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, (1996), Climate Monitoring and Diagnostics Laboratory No.23 Summary Report 1994-1995, Abstract The Climate Monitoring and Diagnostics Laboratory (CMDL) is located in Boulder, Colorado, with observatories in Barrow, Alaska; Mauna Loa, Hawaii; Cape Matatula, American Samoa; and South Pole, Antarctica. It is one of twelve components of the Environmental Research Laboratories (ERL) within the Office of Oceanic and Atmospheric Research (OAR) of the National Oceanic and Atmospheric Administration (NOAA). CMDL conducts research related to atmospheric constituents that are capable of forcing change in the climate of the earth through modification of the atmospheric radiative environment, for example greenhouse gases and aerosols, and those that may cause depletion of the global ozone layer. This report is a summary of activities of CMDL for calendar years 1994 and 1995. It is the 23rd consecutive report issued by this organization and its Air Resources Laboratory/Geophysical Monitoring for Climatic Change predecessor since formation in 1972. From 1972 through 1993 (numbers 1 through 22), reports were issued annually. However, with this issue we begin a 2-year reporting cycle, which stems from a need to most efficiently use the time and financial resources of our staff and laboratory and from a general trend towards electronic media. In this respect, CMDL has developed a comprehensive internet home page during the past 2 years. There you will find information about our major groups and observatories, latest events and press releases, publications, data availability, and personnel. Numerous data graphs and ftp data files are available. The URL address is http://www.cmdl.noaa.gov. Information (program descriptions, accomplishments, publications, plans, data access, etc.) on CMDL parent organizations can best be obtained via the internet. Their URL addresses are ERL: http://www.erl.noaa.gov; OAR: http://www.oar.noaa.gov; NOAA: http://www.noaa.gov. In 1995, Eldon Ferguson retired from federal service and from the CMDL Director's position that he held from the formation of the Laboratory in 1990. On a personal note, we extend to him our best wishes for the future and our thanks for scientific guidance and direction in the past. In 1996, David Hofmann, the CMDL Chief Scientist since 1990, was appointed Director of CMDL. This report is organized into the following major sections: 1. Observatory, Meteorology, and Data Management 2. Carbon Cycle 3. Aerosols and Radiation 4. Ozone and Water Vapor 5. Nitrous Oxide and Halocompounds 6. Cooperative Programs These are followed by a list of CMDL staff publications for 1994-1995
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Barrie, L.A., J.W. Bottenheim, R. C. Schnell, P.J. Crutzen and R.A. Rasmussen, (1988), Ozone destruction and photochemical reactions at polar sunrise in the lower Arctic atmosphere, Nature, 334, 6178, 138-141, doi:10.1038/334138a0 Abstract There is increasing evidence that at polar sunrise sunlight-induced changes in the composition of the lower Arctic atmosphere (0�2 km) are taking place that are important regarding the tropospheric cycles of ozone, bromine, sulphur oxides1, nitrogen oxides2 and possibly iodine3. Here we focus on recent ground-level observations from the Canadian baseline station at Alert (82.5� N, 62.3� W) and from aircraft that show that ozone destruction is occurring under the Arctic surface radiation inversion during March and April as the Sun rises. The destruction might be linked to catalytic reactions of BrOx radicals and the photochemistry of bromoform, which appears to have a biological origin in the Arctic Ocean. This may clarify previously unexplained regular springtime occurrences of ozone depletion at ground level in a 10-year data record at Barrow, Alaska4, as well as peaks in aerosol bromine observed throughout the Arctic in March and April3. Current information does not allow us to offer more than a speculative explanation for the chemical mechanisms leading to these phenomena.
Bender, M.L., D.T. Ho, M.B. Hendricks, R. Mika, M.O. Battle, P. P. Tans, T. J. Conway, B. Sturtevant and N. Cassar, (2005), Atmospheric O2/N2 changes, 1993-2002: Implications for the partitioning of fossil fuel CO2 sequestration, Global Biogeochemical Cycles, 19, 4, GB4017, doi:10.1029/2004GB002410 Abstract Improvements made to an established mass spectrometric method for measuring changes in atmospheric O2/N2 are described. With the improvements in sample handling and analysis, sample throughput and analytical precision have both increased. Aliquots from duplicate flasks are repeatedly measured over a period of 2 weeks, with an overall standard error in each flask of 3�4 per meg, corresponding to 0.6�0.8 ppm O2 in air. Records of changes in O2/N2 from six global sampling stations (Barrow, American Samoa, Cape Grim, Amsterdam Island, Macquarie Island, and Syowa Station) are presented. Combined with measurements of CO2 from the same sample flasks, land and ocean carbon uptake were calculated from the three sampling stations with the longest records (Barrow, Samoa, and Cape Grim). From 1994�2002, We find the average CO2 uptake by the ocean and the land biosphere was 1.7 � 0.5 and 1.0 � 0.6 GtC yr?1 respectively; these numbers include a correction of 0.3 Gt C yr?1 due to secular outgassing of ocean O2. Interannual variability calculated from these data shows a strong land carbon source associated with the 1997�1998 El Ni�o event, supporting many previous studies indicating that high atmospheric growth rates observed during most El Ni�o events reflect diminished land uptake. Calculations of interannual variability in land and ocean uptake are probably confounded by non-zero annual air sea fluxes of O2. The origin of these fluxes is not yet understood.
Bernhard, G., C. R. Booth, J. C. Ehramjian, R. Stone and E. G. Dutton, (2007), Ultraviolet and Visible Radiation at Barrow, Alaska: Climatology and Influencing Factors on the Basis of Version 2 NSF Network Data, Journal of Geophysical Research-Atmospheres, 112, D09101.1-D09101.19, 10.1029/2006JD007865 Abstract Spectral ultraviolet (UV) and visible irradiance has been measured near Barrow, Alaska (71�N, 157�W), between 1991 and 2005 with a SUV-100 spectroradiometer. The instrument is part of the U.S. National Science Foundation's UV Monitoring Network. Here we present results based on the recently produced "version 2" data release, which supersedes published "version 0" data. Cosine error and wavelength-shift corrections applied to the new version increased biologically effective UV dose rates by 0-10%. Corrected clear-sky measurements of different years are typically consistent to within �3%. Measurements were complemented with radiative transfer model calculations to retrieve total ozone and surface albedo from measured spectra and for the separation of the different factors influencing UV and visible radiation. A climatology of UV and visible radiation was established, focusing on annual cycles, trends, and the effect of clouds. During several episodes in spring of abnormally low total ozone, the daily UV dose at 305 nm exceeded the climatological mean by up to a factor of 2.6. Typical noontime UV Indices during summer vary between 2 and 4; the highest UV Index measured was 5.0 and occurred when surface albedo was unusually high. Radiation levels in the UV-A and visible exhibit a strong spring-autumn asymmetry. Irradiance at 345 nm peaks on approximately 20 May, 1 month before the solstice. This asymmetry is caused by increased cloudiness in autumn and high albedo in spring, when the snow covered surface enhances downwelling UV irradiance by up to 57%. Clouds reduce UV radiation at 345 nm on average by 4% in March and by more than 40% in August. Aerosols reduce UV by typically 5%, but larger reductions were observed during Arctic haze events. Stratospheric aerosols from the Pinatubo eruption in 1991 enhanced spectral irradiance at 305 nm for large solar zenith angles. The year-to-year variations of spectral irradiance at 305 nm and of the UV Index are mostly caused by variations in total ozone and cloudiness. Changes in surface albedo that may occur in the future can have a marked impact on UV levels between May and July. No statistically significant trends in monthly mean noontime irradiance were found.
Bodhaine, B. A., (1983), Aerosol measurements at four background sites, Journal of Geophysical Research, 88, C15, 10753-10768, 10.1029/JC088iC15p10753 Abstract Atmospheric monitoring stations are operated at Barrow, Alaska; Mauna Loa, Hawaii; American Samoa; and South Pole by the Geophysical Monitoring for Climatic Change program to measure the characteristics of gaseous and aerosol species under background conditions. A nearly continuous record of light-scattering coefficient and condensation nuclei concentration measurements is available for Barrow since 1971, Mauna Loa since 1974, Samoa since 1977, and South Pole since 1974. The Barrow light-scattering data exhibit a strong annual cycle with a maximum in winter and spring (the Arctic haze) and a minimum in summer. The Barrow condensation nuclei data exhibit a strong semiannual cycle with a maximum coinciding with that of light scattering and an additional maximum about August. The Mauna Loa light-scattering data show a strong annual cycle with a maximum in April or May caused by long-range transport of Asian desert dust. The Mauna Loa condensation nuclei data show no significant annual cycle. The Samoa light-scattering and condensation nuclei data are representative of a clean marine atmosphere and exhibit no significant annual or diurnal cycle. The South Pole light-scattering data show a complicated annual cycle with a maximum in the austral summer and a minimum about April. The austral winter is dominated by events most likely caused by the transport of sea salt in the troposphere from the coastal regions to the interior of the Antarctic continent. The South Pole condensation nuclei data show a repeatable annual cycle with a maximum in the austral summer and a minimum in the austral winter. Linear least squares trend analyses show no significant trend compared to the standard error about the regression line at any station.
Bodhaine, B.A., (1995), Aerosol absorption measurements at Barrow, Mauna Loa and the south pole, Journal of Geophysical Research-Atmospheres, 100, D5, 8967-8975, 95JD00513 Abstract Aerosol absorption (?ap) has been measured continuously using aethalometers at Barrow, Alaska (1986 to present); Mauna Loa, Hawaii (1990 to present); and south pole, Antarctica (1987�1990). These three stations are part of a network of baseline monitoring stations operated by the Climate Monitoring and Diagnostics Laboratory (CMDL) of the National Oceanic and Atmospheric Administration (NOAA). Condensation nucleus (CN) concentration and multiwavelength aerosol scattering (?sp) have also been measured continuously for many years at these stations. Aethalometer measurements are usually reported in terms of atmospheric black carbon aerosol (BC) concentration using the calibration suggested by the manufacturer. Here we deduce the in situ ?ap(550 nm) from aethalometer measurements by assuming that the aerosol absorption on the aethalometer filter is enhanced by a factor of 1.9 over that in the atmosphere. This is consistent with using 19 m2 g?1 for the specific absorption of BC on the aethalometer filter and 10 m2 g?1 for the in situ specific absorption of BC in the atmosphere (the ratio of the two specific absorptions is 1.9). Although these values of specific absorption may vary significantly for different environments, the ratio might be expected to be relatively constant. The single-scattering albedo, defined by ? = ?sp/(?sp + ?ap), has been estimated from the simultaneous measurements of ?ap and ?sp. Furthermore, assuming a 1/? dependence for ?ap in the 450 to 700-nm wavelength region, multiwavelength ?sp measurements allow the estimation of the wavelength dependence of ?. Each station shows a considerable annual cycle in ?ap, ?sp, and ?. The maximum in the Barrow annual cycle is caused primarily by the springtime Arctic haze phenomenon; the maximum in the Mauna Loa annual cycle is caused by the springtime Asian dust transport; and the maximum in the south pole annual cycle is caused by late winter transport from southern midlatitudes. It was found that annual mean values are ?ap = 4.1 � 10?7 m?1 (?41 ng m?3 BC) and ? = 0.96 for Barrow; ?ap = 5.8 � 10?8 m?1 (?5.8 ng m?3 BC) and ? = 0.97 for Mauna Loa; and ?ap = 6.5 � 10 ?9 m?1 (?0.65 ng m?3 BC) and ? = 0.97 for south pole. It was also found that the wavelength dependence of ? may be important at Barrow and south pole, but not important at Mauna Loa.
Bodhaine, B.A., (1989), Barrow surface aerosol: 1976-1986, Atmospheric Environment (1967), 23, 11, 2357-2369, doi:10.1016/0004-6981(89)90249-7 Abstract Measurements at Barrow during the first Arctic Gas and Aerosol Sampling Program (AGASP-I), conducted in March�April 1983, showed a series of aerosol events detected at the ground that coincided with rapid long-range transport paths from Eurasia to the vicinity of Barrow. These events were strongly correlated with aerosol loading in the vertical column (optical depth). Aerosol and meteorological measurements at Barrow during the second AGASP (AGASP-II), conducted in April 1986, indicate no rapid long-range transport from lower-latitude source regions to the vicinity of Barrow, and only limited vertical transport from above the boundary layer to the surface. Aerosol size distribution measurements in the 0.005�0.1 ?m diameter size range using a Nuclepore-filter diffusion battery apparatus showed a median diameter of about 0.01 ?m during times of high condensation nucleus (CN) concentrations and 0.05 ?m during low concentrations. Aerosol black carbon concentrations exceeding 200 ng m?3 were detected at the surface and were more strongly correlated with CN concentrations than with aerosol scattering extinction (?sp), suggesting that aerosol carbon was generally associated with small particles rather than large particles. A continuous record of CN and ?sp measurements is available from 1976 to the present. The ?sp data show a strong annual cycle, having a maximum exceeding 10 ?5 m ?1 in the winter and spring (the Arctic haze), and a minimum of about 10?6m?1 in the summer and fall. The CN data show a semiannual cycle, having a maximum of several hundred per cubic centimeter coinciding with the maximum in ?spin early spring, and a secondary maximum in August. Minima in CN concentration of about 100 cm?3 occur in summer and late fall. No significant diurnal cycle appears in either the CN or ?sp long-term records.
Bodhaine, B. A., E. G. Dutton, J. Deluisi, G. A. Herbert, G. E. Shaw and A. D. A. Hansen, (1987), Surface aerosol measurements at Barrow during AGASP-II, Fourth Symposium on Arctic Air Chemistry, September 29-October 2, 1987, Hurdal, Norway Abstract Measurements at Barrow during the second Arctic Gas and Aerosol Sampling Program (AGASP-II), conducted in April 1986, showed no rapid long-range transport from lower-latitude source regions to Barrow, and only limited vertical transport from above the boundary layer to the surface. New aerosol size distribution measurements in the 0.005�0.1 m diameter size range using a Nuclepore-filter diffusion battery apparatus showed a median diameter of about 0.01 m during times of high condensation nucleus (CN) concentrations. Aerosol black carbon concentrations exceeding 400 ng m�3 were detected at the surface and were more strongly correlated with CN concentrations than with aerosol scattering extinction (sp), suggesting that aerosol carbon was generally associated with small particles rather than large particles. Measurements at Barrow during AGASP-I, conducted in March�April 1983, showed a series of aerosol events detected at the ground that were caused by rapid long-range transport paths to the vicinity of Barrow from Eurasia. These events were strongly correlated with aerosol loading in the vertical column (optical depth).
Bodhaine, B. A., E. G. Dutton, J. Deluisi, G. A. Herbert, G. E. Shaw and A. D. A. Hansen, (1989), Surface aerosol measurements at Barrow during AGASP-II, Journal of Atmospheric Chemistry, 9, 1-3, 213-224, doi:10.1007/BF00052833 Abstract Measurements at Barrow during the second Arctic Gas and Aerosol Sampling Program (AGASP-II), conducted in April 1986, showed no rapid long-range transport from lower-latitude source regions to Barrow, and only limited vertical transport from above the boundary layer to the surface. New aerosol size distribution measurements in the 0.005�0.1 mgrm diameter size range using a Nuclepore-filter diffusion battery apparatus showed a median diameter of about 0.01 mgrm during times of high condensation nucleus (CN) concentrations. Aerosol black carbon concentrations exceeding 400 ng m�3 were detected at the surface and were more strongly correlated with CN concentrations than with aerosol scattering extinction (sgrsp), suggesting that aerosol carbon was generally associated with small particles rather than large particles. Measurements at Barrow during AGASP-I, conducted in March�April 1983, showed a series of aerosol events detected at the ground that were caused by rapid long-range transport paths to the vicinity of Barrow from Eurasia. These events were strongly correlated with aerosol loading in the vertical column (optical depth).
Bodhaine, B. A., E. G. Dutton and J. J. DeLuisi, (1984), Surface aerosol measurements at Barrow during AGASP, Geophys. Res. Lett., 11, 5, 377-380, 10.1029/GL011i005p00377 Abstract Surface aerosol measurements were made at the Barrow GMCC Observatory during the AGASP flight series in March 1983. The condensation nucleus, scattering extinction coefficient, size distribution, and total aerosol optical depth measurements all clearly show conditions of background Arctic haze for March 9‐11, a series of haze episodes during March 12‐16, and a return to background haze for March 17‐18. Angstrom exponents calculated from scattering coefficient data were low during March 9‐11, relatively higher during March 12‐14, and highest during March 15‐18. Surface aerosol data and aerosol optical depth data are in good qualitative agreement for the 10‐day period studied. Background haze was present when trajectories circled the Arctic basin, and haze episodes occurred when trajectories originated in western Asia and Europe.
Bodhaine, B.A., J. M. Harris and G.A. Herbert, (1981), Aerosol light scattering and condensation nuclei measurements at Barrow, Alaska, Second Symposium on Arctic Air Chemistry, May 6-8, 1980, Kingston, RI Abstract N.O.A.A.'s Geophysical Monitoring for Climatic Change Program operates a background monitoring station at Barrow, Alaska. Continuous measurements of aerosols, gases, solar radiation and meteorological parameters are made in an effort to understand their possible long term effects on climate. The aerosol program consists of continuous measurements of integrated light scattering and condensation nuclei (CN) using a four wavelength nephelometer and an automatic CN counter. Light scattering data show an annual cycle with a maximum above 10?5 m?1 in March and a minimum of about 10?6 m?1 in June. Condensation nuclei data show a semi-annual change with monthly mean concentration ranging between 500 and 40 cm?3, maxima in March and August, and minima in June and September. Local aerosol sources have been identified by calculating CN concentration as a function of local wind direction and presenting the results on a 36 point wind rose. Local sources are clearly identified to the north, west and southwest of the observatory site and may be associated with local activities and population centers. A clean air sector may be defined on the wind rose, and pollution episodes may be defined in terms of short term variability of the CN concentration. Large scale 10-day back trajectories have been analysed for Barrow and it is found that light scattering and condensation nuclei concentration are higher when trajectories originate north of the station than when trajectories originate south of the station. Anomalous trajectories from north of the station in August coincide with an anomalous peak in condensation nuclei.
Bodhaine, B. A., J. M. Harris and G. A. Herbert, (1981), Aerosol light scattering and condensation nuclei measurements at Barrow, Alaska, Atmospheric Environment (1967), 15, 8, 1375-1389, 10.1016/0004-6981(81)90344-9 Abstract N.O.A.A.'s Geophysical Monitoring for Climatic Change Program operates a background monitoring station at Barrow, Alaska. Continuous measurements of aerosols, gases, solar radiation and meteorological parameters are made in an effort to understand their possible long term effects on climate. The aerosol program consists of continuous measurements of integrated light scattering and condensation nuclei (CN) using a four wavelength nephelometer and an automatic CN counter. Light scattering data show an annual cycle with a maximum above 10?5 m?1 in March and a minimum of about 10?6 m?1 in June. Condensation nuclei data show a semi-annual change with monthly mean concentration ranging between 500 and 40 cm?3, maxima in March and August, and minima in June and September. Local aerosol sources have been identified by calculating CN concentration as a function of local wind direction and presenting the results on a 36 point wind rose. Local sources are clearly identified to the north, west and southwest of the observatory site and may be associated with local activities and population centers. A clean air sector may be defined on the wind rose, and pollution episodes may be defined in terms of short term variability of the CN concentration. Large scale 10-day back trajectories have been analysed for Barrow and it is found that light scattering and condensation nuclei concentration are higher when trajectories originate north of the station than when trajectories originate south of the station. Anomalous trajectories from north of the station in August coincide with an anomalous peak in condensation nuclei.
Bodhaine, B.A. and E. G. Dutton, (1993), A Long term decrease in Arctic Haze at Barrow, Alaska, Geophysical Research Letters, 20, 10, 947-950, 93GL01146 Abstract Surface aerosol scattering measurements have been conducted at Barrow, Alaska, from May 1976 to the present using a four?wavelength nephelometer. Total column aerosol optical depth measurements have been obtained over the same time period. Both data sets show a maximum in 1982 and then a decreasing trend to the present. This decreasing trend is apparent, and statistically significant, only in March�April. Arctic haze, caused by long?range transport from midlatitude industrial regions, is most evident in the vicinity of Barrow during this time of year. We suggest that the decrease in Arctic haze at Barrow, as observed in the aerosol light scattering and optical depth records, is due to decreased anthropogenic pollution emissions in Europe and the former Soviet Union, the primary source regions for the springtime aerosol at Barrow. Volcanic effects in the stratosphere have been subtracted from the optical depth data, and are not believed to be significant in the surface?based data.
Bridgman, H.A. and B.A. Bodhaine, (1994), On the frequency of long-range transport events at point barrow, Alaska, 1983-1992, Atmospheric Environment, 28, 21, 3537-3549, doi:10.1016/1352-2310(94)90010-8 Abstract The Point Barrow, Alaska pollutant and meteorological data bases from the Climate Monitoring and Diagnostics Laboratory (CMDL) baseline station are evaluated for the first 120 days of each year between 1983 and 1992. The purpose of this study is to investigate whether a relationship between gaseous and aerosol pollutants during clean sector winds could be used to indicate periods of long-range transport of pollutants. Representative pollutant parameters used include carbon dioxide and aerosol light scattering (?sp), with methane, condensation nuclei, and black carbon used in support. Several interesting relationships emerge between the gases and ?sp during long-range transport events: (1) the frequency of clean sector winds for most months is greater than 70%, with the range 31.6�92.8%; (2) high correlations between CO2 and ?sp do not necessarily occur during long-range transport events, and the relationship between the two parameters is weak and erratic; (3) a considerable majority of transport periods occur in January and March, with the highest frequency in the AGASP measurement years 1983 and 1986, in some contrast to previous analysis using only haze as the pollution indicator; (4) pollution reaching surface monitors at Point Barrow most often originates from pooled air in the Arctic Basin, with no clear definition of more distant source regions.
Brock, C. A., J. Cozic, R. Bahreini, K. D. Froyd, A. M. Middlebrook, A. McComiskey, J. Brioude, O. R. Cooper, A. Stohl, K. C. Aikin, J. A. de Gouw, D. W. Fahey, R. A. Ferrare, R.-S. Gao, W. Gore, J. S. Holloway, G. Hübler, A. Jefferson, D. A. Lack, S. Lance, R. H. Moore, D. M. Murphy, A. Nenes, P. C. Novelli, J. B. Nowak, J. A. Ogren, J. Peischl, R. B. Pierce, P. Pilewskie, P. K. Quinn, T. B. Ryerson, K. S. Schmidt, J. P. Schwarz, H. Sodeman, J. R. Spackman, H. Stark, D. S. Thomson, T. Thornberry, P. Veres, L. A. Watts, C. Warneke and A. G. Wollny, (2011), Characteristics, sources, and transport of aerosols measured in spring 2008 during the aerosol, radiation, and cloud processes affecting Arctic Climate (ARCPAC) Project, Atmospheric Chemistry and Physics, 11, 6, 2423-2553, 10.5194/acp-11-2423-2011 Abstract We present an overview of the background, scientific goals, and execution of the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project of April 2008. We then summarize airborne measurements, made in the troposphere of the Alaskan Arctic, of aerosol particle size distributions, composition, and optical properties and discuss the sources and transport of the aerosols. The aerosol data were grouped into four categories based on gas-phase composition. First, the background troposphere contained a relatively diffuse, sulfate-rich aerosol extending from the top of the sea-ice inversion layer to 7.4 km altitude. Second, a region of depleted (relative to the background) aerosol was present within the surface inversion layer over sea-ice. Third, layers of dense, organic-rich smoke from open biomass fires in Southern Russia and Southeastern Siberia were frequently encountered at all altitudes from the top of the inversion layer to 7.1 km. Finally, some aerosol layers were dominated by components originating from fossil fuel combustion. Of these four categories measured during ARCPAC, the diffuse background aerosol was most similar to the average springtime aerosol properties observed at a long-term monitoring site at Barrow, Alaska. The biomass burning (BB) and fossil fuel layers were present above the sea-ice inversion layer and did not reach the sea-ice surface during the course of the ARCPAC measurements. The BB aerosol layers were highly scattering and were moderately hygroscopic. On average, the layers produced a noontime net heating of ~0.1 K day?1 between 2 and 7 km and a~slight cooling at the surface. The ratios of particle mass to carbon monoxide (CO) in the BB plumes, which had been transported over distances >5000 km, were comparable to the high end of literature values derived from previous measurements in fresh wildfire smoke. These ratios suggest minimal precipitation scavenging and removal of the BB particles between the time they were emitted and the time they were observed in dense layers above the sea-ice inversion layer.
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Conway, T. J. and L. P. Steele, (1989), Carbon dioxide and methane in the Arctic atmosphere, Journal of Atmospheric Chemistry, 9, 1-3, 81-99, doi:10.1007/BF00052826 Abstract Fifty flask air samples were taken during April 1986 from a NOAA WP-3D Orion aircraft which flew missions across a broad region of the Arctic as part of the second Arctic Gas and Aerosol Sampling Program (AGASP II). The samples were subsequently analyzed for both carbon dioxide (CO2) and methane (CH4). The samples were taken in well-defined layers of Arctic haze, in the background troposphere where no haze was detected, and from near the surface to the lower stratosphere. Vertical profiles were specifically measured in the vicinity of Barrow, Alaska to enable comparisons with routine surface measurements made at the NOAA/GMCC observatory. Elevated levels of both methane and carbon dioxide were found in haze layers. For samples taken in the background troposphere we found negative vertical gradients (lower concentrations aloft) for both gases. For the entire data set (including samples collected in the haze layers) we found a strong positive correlation between the methane and carbon dioxide concentrations, with a linear regression slope of 17.5 ppb CH4/ppm CO2, a standard error of 0.6, and a correlation coefficient (r2) of 0.95. This correlation between the two gases seen in the aircraft samples was corroborated by in situ surface measurements of these gases made at the Barrow observatory during March and April 1986. We also find a similar relationship between methane and carbon dioxide measured concurrenty for a short period in the moderately polluted urban atmosphere of Boulder, Colorado. We suggest that the strong correlation between methane and carbon dioxide concentrations reflects a common source region for both, with subsequent long-range transport of the polluted air to the Arctic.
Curtis, J., G. Wendler, R. S. Stone and E. G. Dutton, (1998), Precipitation decrease in the western Arctic, with special emphasis on Barrow and Barter Island, Alaska, International Journal of Climatology, 18, 15, 1687-1707, doi:10.1002/(SICI)1097-0088(199812)18:15<1687::AID-JOC341>3.0.CO;2-2 Abstract Over the Arctic during the last few decades a decrease in annual precipitation and snow depths have been observed; this decrease is especially pronounced during the winter months. This decrease was not only found over northern Alaska but also over the high latitude Canadian stations and Russian drift stations. Further, satellite monitoring of North America snow cover has revealed a significant decreasing trend in mid-spring cover since 1972. The temperature increased during the last few decades in the Arctic, hence the simplest explanation - normally increased temperature leads to high precipitation - is not valid. A causal explanation for these trends had been related to the shift of the Aleutian low and Arctic high. This study, with special emphasis on the surface observation data from Barrow and Barter Island, indicates: (i) not only the frequency, but the mean intensity of precipitation has decreased; (ii) the amount of total cloud cover, and in particular, low cloudiness, has decreased with time; (iii) sea-level pressure did not show any significant trends. Variability in atmospheric pressure, however, decreased with time, suggesting that either the intensity and/or frequency of cyclones has decreased; (iv) a shift in seasonal resultant winds at Barrow has been observed.
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Delene, D. J. and J. A. Ogren, (2002), Variability of Aerosol Optical Properties at Four North American Surface Monitoring Sites, Journal of the Atmospheric Sciences, 59, 6, 1135-1150, doi:10.1175/1520-0469(2002)059<1135:VOAOPA>2.0.CO;2 Abstract Aerosol optical properties measured over several years at surface monitoring stations located at Bondville, Illinois (BND); Lamont, Oklahoma (SGP); Sable Island, Nova Scotia (WSA); and Barrow, Alaska (BRW), have been analyzed to determine the importance of the variability in aerosol optical properties to direct aerosol radiative forcing calculations. The amount of aerosol present is of primary importance and the aerosol optical properties are of secondary importance to direct aerosol radiative forcing calculations. The mean aerosol light absorption coefficient (?ap) is 10 times larger and the mean aerosol scattering coefficient (?sp) is 5 times larger at the anthropogenically influenced site at BND than at BRW. The aerosol optical properties of single scattering albedo (?o) and hemispheric backscatter fraction (b) have variability of approximately �3% and �8%, respectively, in mean values among the four stations. To assess the importance of the variability in ?o and b on top of the atmosphere aerosol radiative forcing calculations, the aerosol radiative forcing efficiency (?F/?) is calculated. The ?F/? is defined as the aerosol forcing (?F) per unit optical depth (?) and does not depend explicitly on the amount of aerosol present. Based on measurements at four North American stations, radiative transfer calculations that assume fixed aerosol properties can have errors of 1%�6% in the annual average forcing at the top of the atmosphere due to variations in average single scattering albedo and backscatter fraction among the sites studied. The errors increase when shorter-term variations in aerosol properties are considered; for monthly and hourly timescales, errors are expected to be greater than 8% and 15%, respectively, approximately one-third of the time. Systematic relationships exist between various aerosol optical properties [?ap, ?o, b, ?F/?, and �ngstr�m exponent (�)] and the amount of aerosol present (measured by ?sp) that are qualitatively similar but quantitatively different among the four stations. These types of systematic relationships and the regional and temporal variations in aerosol optical properties should be considered when using �climatological� averages.
Dlugokencky, E. J., L. P. Steele, P. M. Lang and K. A. Masarie, (1995), Atmospheric methane at Mauna Loa and Barrow observatories: Presentation and analysis of in situ measurements, Journal of Geophysical Research-Atmospheres, 100, d11, 23103-23113, doi:10.1029/95JD02460 Abstract In situ methane (CH4) measurement techniques and data from the NOAA Climate Monitoring and Diagnostics Laboratory observatories at Mauna Loa, Hawaii, and Barrow, Alaska, are presented. For Mauna Loa, the data span the time period April 1987 to April 1994. At Barrow the measurements cover the period January 1986 to January 1994. Sixty air samples per day were measured with a fully automated gas chromatograph using flame ionization detection. Details of the experimental methods and procedures are given. Data are presented and assessed over various timescales. The average peak to peak seasonal cycle amplitudes obtained from four harmonics fitted to the detrended data were 25.1 ppb at Mauna Loa and 47.2 ppb at Barrow. When the seasonal cycle amplitude during each calendar year was determined as the difference between the maximum and minimum value from a smooth curve fitted to the data, the average amplitudes were (30.6 �4.2) ppb at Mauna Loa and (57.5 � 11.4) ppb at Barrow. A discrepancy exists between these two methods due to the temporal variability in the positions of the seasonal maxima. The average trend at Mauna Loa was 9.7 ppb yr?1, but this trend was observed to decrease at a rate of 1.5 ppb yr?2. For Barrow the average trend was 8.5 ppb yr?1, and the rate of decrease in the trend was 2.1 ppb yr?2. At Mauna Loa, a diurnal cycle was sometimes observed with an amplitude of up to 10 ppb when averaged over 1 month.
Dutton, E. G., A. Farhadi, R. S. Stone, C. Long and D. W. Nelson, (2004), Long-term variations in the occurrence and effective solar transmission of clouds as determined from surface-based total irradiance observations, Journal of Geophysical Research-Atmospheres, 109, d3, D03204-D03204, doi:10.1029/2003JD003568 Abstract [1] Time series of cloud solar transmission and cloud occurrence frequency are developed for the past 27 years at four globally remote and climatically diverse surface locations. A new methodology is developed that objectively segregates times of cloud-free conditions from those times when clouds are detected in high-time-resolution total solar irradiance observations that are obtained from pyranometers. The methodology for cloud detection depends on the magnitude and short-term variability of observed departures from clear-sky conditions. Expected clear-sky irradiances are based on interpolated clear-sky observations. Results of the new cloud detection methodology are compared to four independent cloud detection methods. An effective cloud transmission is determined as the ratio of observed irradiance in the presence of clouds to that expected in the absence of clouds. Selective forward scattering by clouds toward the observation site results in computed effective transmissions frequently being >1.0. It is shown that conditional temporal averaging of effective cloud transmission over periods of three days or more virtually eliminates the unrealistic cloud transmissions exceeding 1.0. Such temporal averaging of the surface measurements is advantageous for comparing against other area-wide cloud transmission estimates, such as those determined from satellite or by numerical climate models. The cloud occurrence frequency and the effective solar transmission for long-term observational records are summarized into monthly and annual averages, and their long-term variability is investigated. Temporal variations in frequency distributions of transmission are used to determine which clouds are responsible for changes in mean cloudiness. A statistically significant upward trend in cloud occurrence frequency, from 76 to 82% between 1976 and 2001, is detected at Barrow, Alaska, where clouds having solar transmission near 0.2 exhibit the largest increase. At the South Pole, decadal timescale oscillations in both cloud characteristics are detected, but no particular cloud category is identified as the source of that oscillation.
Dutton, E. G., J. Deluisi and B. A. Bodhaine, (1984), Features of Aerosol Optical Depth Observed at Barrow, March 10-20, Geophysical Research Letters, 11, 5, 385-388, Abstract Total vertical aerosol optical depth over Barrow, Alaska, during March 1983 was up to four times greater than the average for recent years, with part of the excess being due to stratospheric debris from El Chichon. The variability in optical depth during a 10?day period spanning the aircraft flights of the Arctic Gas and Aerosol Sampling Program (AGASP) suggests a major tropospheric aerosol event on March 12 and 13, which accounts for the maximum observed optical depths. Occurrence of the tropospheric event is substantiated with independent aerosol data from aircraft, surface sampling, and synoptic scale meteorological data. Analysis of the Barrow optical depth data yields information on the climatic effects of both the stratospheric aerosol from El Chichon and the tropospheric aerosol commonly called Arctic haze.
Dutton, E. G. and D. Endres, (1991), Date of Snowmelt at Barrow, Alaska, U.S.A., Arctic and Alpine Research, 23, 1, 115-119, Abstract The date of snowmelt near Barrow, Alaska, for recent years is determined from radiometric in situ measurements of the tundra solar albedo. The snowmelt dates determined from the albedo measurements dispute recently published values based on routine visual observations at the Barrow National Weather Service (NWS) Office. Local heat-budget-altering effects of the village and its recent abrupt growth are suggested as the cause for the disagreement between the rural albedo and NWS "in town" observations. The open tundra albedo measurements combined with historical NWS observations suggest that there is no significant trend in the date of snowmelt near Barrow.
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Elliott, W. P., J. K. Angell and K. W. Thoning, (1991), Relation of atmospheric CO2 to tropical sea and air temperatures and precipitation, Tellus B, 43B, 2, 144-155, 10.1034/j.1600-0889.1991.00009.x Abstract Associations between the season-to-season changes in CO2 concentration and the sea-surface temperature in the eastern equatorial Pacific, the tropospheric air temperature, and the precipitation in the tropics are explored. The CO2 records at Mauna Loa and the South Pole from the Scripps Institution of Oceanography and the GMCC/NOAA program, as well as the GMCC records at Barrow, Alaska and American Samoa were used after the annual cycle and the growth due to fossil fuel emission has been removed. We find that the correlation between CO2 changes and each of the other variables changes with time. In particular, the period from about 1968 to about 1978 was the period of highest correlation, which was also the period when the climate variables were best correlated with each other. The air temperature and the precipitation were as well correlated with CO2 changes as was SST. Also, there are individual seasons when the CO2 changes are much better correlated with the climate variables than at other seasons. Furthermore, El Ni�o events, while the source of the largest signal in the CO2 record, are by no means the same from one event to the next. We take these results as further confirmation that the apparent effect of SST on the CO2 record comes less from changes in the equatorial eastern Pacific Ocean than from climate changes throughout the globe. Climate effects on the terrestrial biosphere seem a likely source of much of the interannual variation in atmospheric CO2.
Endres, D., (1995), GPS-derived time baffles NOAA researcher, Ocean Navigator, , , Abstract Recently, I discovered that time derived from GPS satellites was not quite in step with other time sources. I am presently doing research at the Climate Monitoring and Diagnostics Lab near Pt. Barrow, Alaska (located at 71� 19' N, 156� 37' W). This facility is maintained by the National Oceanographic and Atmospheric Administration and is part of the network of sites designed to monitor meteorological conditions and background atmospheric constituents for detecting changes in worldwide pollution levels and monitoring the effect of these changes on global climate.
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Foster, J., J. Winchester and E. G. Dutton, (1992), The Date of Snow Disappearance on the Arctic Tundra as Determined from Satellite, Meteorological Station and Radiometric insitu Observations, IEEE Transactions on Geoscience and Remote Sensing, 30, 4, 793-798, Abstract In this study satellite-derived snow cover maps for sites in Alaska, Canada, Scandinavia, and Siberia were employed to assess the date when snow disappeared on the Arctic tundra and to determine ir the snow has been melting earlier in the spring in more recent years. Results show that for three of the four sites there has been a tendency toward earlier snowmelt during the 1980's. In Alaska, the satellite-derived date of snowmelt was compared to the date of snowmelt as observed at the Barrow meteorological station and a site near Barrow where radiometric in situ measurements were made for the last 5 years. The three data sources complement each other even though the satellite site is located 150 km from Barrow. One mechanism which could cause a trend toward earlier snowmelt in Alaska is the deposition of soot and particulates on the snow surface as a result of Arctic haze.
G
Garrett, T. J., C. Zhao and P. C. Novelli, (2010), Assessing the relative contributions of transport efficiency and scavenging to seasonal variability in Arctic aerosol, TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY, 62, 190-196, 10.1111/j.1600-0889.2010.00453.x Abstract Regional aerosol concentrations are governed by an evolving balance between aerosol sources and sinks. Here, a simple technique is described for making estimates of the extent to which seasonal aerosol variability is controlled by wet scavenging rather than the efficiency of transport from pollution source regions. Carbon monoxide (CO) is employed as an assumed passive tracer of pollution transport efficiency, to which the magnitude of aerosol light scattering is compared. Because aerosols, unlike CO, are affected by wet scavenging as well as transport efficiency, the ratio of short-term perturbations in these two quantities provides a measure of the relative roles of these two processes. This technique is applied to surface measurements in the Arctic at Barrow, Alaska (71�N) for the decade between 2000 and 2009. What is found is that a well-known seasonal cycle in �Arctic Haze� is dominated by variability in wet scavenging. Crossing the freezing threshold for warm rain production appears particularly critical for efficiently cleaning the air.
H
Halter, B. and J. M. Harris, (1983), On the variability of atmospheric carbon dioxide concentration at Barrow, Alaska, during winter, Journal of Geophysical Research, 88, C11, 6858-6864, Abstract Winter variability over periods of 1 to 5 days in surface CO2 concentration at Barrow, Alaska was studied by examining the relation between CO2 concentration and air mass. The largest positive anomalies of CO2 concentration occurred with relatively deep surface-based Arctic air masses. The long residence time in the Arctic of these air masses is qualitatively compatible with both a natural CO2 source, such as the Arctic Ocean, and transport of anthropogenic CO2 from mid-latitudes in a manner similar to that proposed for the Arctic haze. Trajectories suggest that the anthropogenic CO2 source region of eastern Asia does not contribute significantly to the positive anomalies. The largest negative CO2 anomalies were associated with the influx of air from the North Pacific or North Atlantic regions above a shallow surface-based Arctic layer. The moisture sounding data suggest mixing or diffusion of this air aloft to the surface through the inversion layer.
Halter, B. C. and J. T. Peterson, (1981), On the variability of atmospheric carbon dioxide concentration at Barrow, Alaska, during summer, Atmospheric Environment (1967), 15, 8, 1391-1399, 10.1016/0004-6981(81)90345-0 Abstract Atmospheric carbon dioxide data obtained at Barrow, Alaska for the May�September period of 1978 were studied to understand the causes of the day-to-day and within-day variations. Sixteen instances of 24-h change in average CO2 concentration of from 15 to 50% of the annual range (approx. 14 ppm) were identified. Within-day variations of up to 50% of the annual range were noted. The variations were found to be related to local and synoptic scale meteorology interacting with local and regional sources and sinks of CO2. The results are consistent with an overall source of CO2 in the tundra of the Alaskan North Slope and a significant sink for CO2 in the ice-free areas of the seas bordering Alaska. The analysis provides an interpretation of the Barrow CO2 record which can be used in the selection of representative data for studying large scale trends.
Hansen, A. D. A., T. J. Conway, L. P. Steele, B. A. Bodhaine, K. W. Thoning, P. P. Tans and T. Novakov, (1989), Correlations among combustion effluent species at Barrow, Alaska: Aerosol black carbon, carbon dioxide, and methane, Journal of Atmospheric Chemistry, 9, 283-299, 10.1007/BF00052838 Abstract As part of the second Arctic Gas and Aerosol Sampling Program (AGASP II) continuous measurements of atmospheric aerosol black carbon (BC) were made at the NOAA/GMCC observatory at Barrow, Alaska (71�19N, 156�36W) during the period March 21�April 22, 1986. Black carbon is produced only by incomplete combustion of carbonaceous materials and so is a particularly useful atmospheric indicator of anthropogenic activities. The BC data have been analyzed together with the concurrent measurements of carbon dioxide (CO2), methane (CH4), and condensation nuclei (CN) that are routinely made at the observatory. All four species showed elevated and highly variable concentrations due to local human activities, principally in the township of Barrow, 7 km to the southwest, and at the DEW Line radar installation 1 km to the northwest. We distinguish between those periods of the record that are affected by local activities and those that are not, on the basis of the short-term (periods of up to 1 hour) variability of the continuous CO2 and CN records, with large short-term variabilities indicating local sources. We identified seven periods of time (events) with durations ranging from 13 to 37 hours when the BC, CO2, and CH4 concentrations changed smoothly over time, were highly correlated with each other, and were not influenced by local activities. These events had BC/CO2 ratios in the range (50�103)�10�6. These ratios are dimensionless since we convert the CO2 concentrations to units of ng m�3 of carbon. Such values of BC/CO2 are characteristic of the combustion effluent from large installations burning heavy fuel oil or coal, automobiles, and domestic-scale natural gas usage. We conclude that these events are indicative of air masses that have been polluted with combustion emissions in a distant location and then transported to the Arctic. In the absence of species-selective loss mechanisms, these air masses will maintain their combustion effluent signatures during the transport. The BC/CO2 ratios found for the local combustion activities are consistent with those expected from known combustion processes.
Harris, J. M., (1984), Trajectories during AGASP, Geophysical Research Letters, 11, 5, 453-456, 10.1029/GL011i005p00453 Abstract Atmospheric trajectories were calculated for various Arctic locations for March and April 1983, during the Arctic Gas and Aerosol Sampling Program (AGASP). Ten?day back trajectories arriving twice daily were calculated on the 850?, 700?, and 500?mb isobaric surfaces. During AGASP flights 1?4, trajectories arriving at Barrow show that flow was over the pole from western Asia and Europe, and that the strongest winds and least vertical wind shear were on March 14 at 0000 UT. Surface aerosols and optical depth measured at this time at Barrow reflect a significant haze episode. Trajectories arriving along the flight tracks north of Barrow were frequently very different from those arriving at Barrow, indicating that source areas were in northeast Asia. Trajectories arriving along AGASP flight track 8 near Svalbard showed that the source area changed dramatically in the approximate location of an Arctic aerosol/haze front.
Harris, J. M., E. J. Dlugokencky, S. J. Oltmans, P. P. Tans, T. J. Conway, P. C. Novelli, K. W. Thoning and J.D.W. Kahl, (2000), An interpretation of trace gas correlations during Barrow, Alaska, winter dark periods, 1986-1997, Journal of Geophysical Research-Atmospheres, 105, D13, 17267-17278, JD900167 Abstract Positive correlations among CO, CO2, and CH4 during winter-spring have been observed at Barrow, Alaska, for many years. We examine these, as well as negative correlations between O3 and these gases, during the winter dark period. Because biogenic and photochemical processes are limited within this environment, we believe that pollution is driving these relationships. The dearth of mixing processes within the Arctic basin, the strong stability of the winter boundary layer, and lack of sunlight (and hence low OH) contribute to the winter-spring maxima in CO, CO2, and CH4. We hypothesize that the negative correlation of O3 with these gases is the result of O3 titration by NO and NO2 (NO x ) in industrial plumes, which leads to the destruction of one to two molecules of O3 per NO emitted. Using the empirical slopes of O3/CO2 and O3/CO determined from 12 years of Barrow data, we derived emission factors, NO x /CO2 and NO x /CO, assuming -1.5 O3/NO because of titration. Comparing these with published emission factors for NO x , CO2, and CO from industrial processes, we found good agreement. This pollution signature is regionally widespread, although air parcels transported from the direction of Siberia have the highest mixing ratios of pollutant gases. Possible scenarios leading to these trace gas relationships are explored.
Harris, J. M. and J.D.W. Kahl, (1994), Analysis of 10-day isentropic flow patterns for Barrow, Alaska: 1985-1992, Journal of Geophysical Research-Atmospheres, 99, D12, 25845-25855, 94JD02324 Abstract Atmospheric transport patterns to Barrow, Alaska, during 1985-1992 were investigated using a newly developed isentropic air trajectory model. The new model features a layeraveraged mode that is activated whenever an air parcel traveling isentropically approaches the Earth's surface. A dynamic preprocessing program ensures that trajectories always arrive at a constant, predetermined altitude. Ten-day back trajectories arriving twice daily at 500, 1500, and 3000 m above sea level revealed no long-term trends in flow patterns during the 8-year period. Frequency of transport type was fairly stable from year to year, except in the anomalously warm year of 1989 when increased numbers of trajectories from the Aleutian region were observed. During the Arctic haze season, trajectories suggest that transport of pollution from north central Russia occurs near the surface (about 20% frequency), whereas that from northern Europe occurs at higher elevations (about 10% frequency).
Helmig, D, S. J. Oltmans, D CARLSON, J LAMARQUE, A JONES, C LABUSCHAGNE, K ANLAUF and K HAYDEN, (2007), A review of surface ozone in the polar regions, Atmospheric Environment, 41, 24, 5138-5161, doi:10.1016/j.atmosenv.2006.09.053 Abstract Surface ozone records from ten polar research stations were investigated for the dependencies of ozone on radiative processes, snow-photochemisty, and. synoptic and stratospheric transport. A total of 146 annual data records for the Arctic sites Barrow, Alaska; Summit, Greenland; Alert, Canada; Zeppelinfjellet, Norway; and the Antarctic stations Halley, McMurdo, Neumayer, Sanae, Syowa, and South Pole were analyzed. Mean ozone at the Northern Hemisphere (NH) stations (excluding Summit) is similar to 5ppbv higher than in Antarctica. Statistical analysis yielded best estimates for the projected year 2005 median annual ozone mixing ratios, which for the Arctic stations were 33.5 ppbv at Alert, 28.6 ppbv at Barrow, 46.3ppbv ppb at Summit and 33.7ppbv at Zeppelinfjellet. For the Antarctic stations the corresponding ozone mixing ratios were 21.6 ppbv at Halley, 27.0 ppbv at McMurdo, 24.9 ppbv at Neumayer, 27.2 ppbv at Sanae, 29.4 ppbv at South Pole, and 25.8 ppbv at Syowa. At both Summit (3212m asl) and South Pole (2830m asl), annual mean ozone is higher than at the lower elevation and coastal stations. A trend analysis revealed that all sites in recent years have experienced low to moderate increases in surface ozone ranging from 0.02 to 0.26 ppbv yr(-1), albeit none of these changes were found to be statistically significant trends. A seasonal trend analysis showed above-average increases in ozone during the spring and early summer periods for both Arctic (Alert, Zeppelinfjellet) and Antarctic (McMurdo, Neumayer, South Pole) sites. In contrast, at Barrow, springtime ozone has been declining. All coastal stations experience springtime episodes with rapid depletion of ozone in the boundary layer, attributable to photochemically catalyzed ozone depletion from halogen chemistry. This effect is most obvious at Barrow, followed by Alert. Springtime depletion episodes are less pronounced at Antarctic stations. At South Pole, during the Antarctic spring and summer, photochemical ozone production yields frequent episodes with enhanced surface ozone. Other Antarctic stations show similar, though less frequent spring and summertime periods with enhanced ozone. The Antarctic data provide evidence that austral spring and summertime ozone production in Antarctica is widespread, respectively, affects all stations at least through transport events. This ozone production contributes to a several ppbv enhancement in the annual mean ozone over the Antarctic plateau; however, it is not the determining process in the Antarctic seasonal ozone cycle. Although Summit and South Pole have many similarities in their environmental conditions, this ozone production does not appear to be of equal importance at Summit. Amplitudes of diurnal, summertime ozone cycles at these polar sites are weaker than at lower latitude locations. Amplitudes of seasonal ozone changes are larger in the Southern Hemisphere (by similar to 5 ppbv), most likely due to less summertime photochemical ozone loss and more transport of ozone-rich air to the Arctic during the NH spring and summer months.
Helmig, D., Patrick Boylan, Bryan Johnson, Sam Oltmans, Chris Fairall, Ralf Staebler, Andrew Weinheimer, John Orlando, David J. Knapp, Denise D. Montzka, Frank Flocke, Udo Frieß, Holger Sihler and Paul B. Shepson, (2012), Ozone dynamics and snow-atmosphere exchanges during ozone depletion events at Barrow, Alaska, J. Geophys. Res., 117, D20, D20303, 10.1029/2012JD017531 Abstract The behavior of lower atmospheric ozone and ozone exchanges at the snow surface were studied using a suite of platforms during the Ocean-Atmosphere-Sea Ice-Snow (OASIS) Spring 2009 experiment at an inland, coastal site east of Barrow, Alaska. A major objective was to investigate if and how much chemistry at the snow surface at the site contributes to springtime ozone depletion events (ODEs). Between March 8 and April 16, seven ODEs, with atmospheric ozone dropping below 1.0 ppbv, were observed. The depth of the ozone-depleted layer was variable, extending from the surface to ∼200–800 m. ODEs most commonly occurred during low wind speed conditions with flow coming from the Arctic Ocean. Two high-sensitivity ozone chemiluminescence instruments were used to accurately define the remaining sub-ppbv ozone levels during ODEs. These measurements showed variable residual ODE ozone levels ranging between 0.010 and 0.100 ppbv. During the most extended ODE, when ozone remained below 1.0 ppbv for over 78 h, these measurements showed a modest ozone recovery or production in the early afternoon hours, resulting in increases in the ozone mixing ratio of 0.100 to 0.800 ppbv. The comparison between high-sensitivity ozone measurements and BrO measured by longpath differential absorption spectroscopy (DOAS) during ODEs indicated that at low ozone levels formation of BrO is controlled by the amount of available ozone. Measurements of ozone in air drawn from below the snow surface showed depleted ozone in the snowpack, with levels consistently remaining <6 ppbv independent of above-surface ambient air concentrations. The snowpack was always a sink of ozone. Ozone deposition velocities determined from ozone surface flux measurements by eddy covariance were on the order of 0.01 cm s−1, which is of similar magnitude as ozone uptake rates found over snow at other polar sites that are not subjected to ODEs. The results from these multiple platform measurements unequivocally show that snow-atmosphere chemical exchanges of ozone at the measurement site do not exhibit a major contribution to ozone removal from the boundary layer and the formation of ODE.
Herbert, G., J. M. Harris and B.A. Bodhaine, (1989), Atmospheric transport during agasp-ii: the Alaskan flights (2-10 April 1986), Atmospheric Environment (1967), 23, 11, 2521-2536, doi:10.1016/0004-6981(89)90264-3 Abstract Kinematic trajectories were computed on isentropic surfaces, in the upwind direction, to determine the origin of the air masses sampled during the Alaskan phase of AGASP-II (Arctic Gas and Aerosol Sampling Program) flights. Gridded wind data from the National Meteorological Center were used to compute the trajectories. Trajectories were computed from the centers of the haze layers and regions of high CN concentration whenever possible. Below 1.5 km, in the presence of large-scale ascending motion, the isentropic surfaces descended to below the lowest level for which temperatures were available. In these situations it was not possible to compute trajectories for more than 2�4 days (1000�2000 km). Otherwise, trajectories were computed for 10 days, at 10-K intervals to the lower stratosphere. The Alaskan AGASP-II flights consisted of research flights to Barrow on 2�3 and 9�10 April, and to over the Beaufort Sea, north of Barter Island, on 8 April 1986. During the 2�3 April flight a major haze event was encountered 900 km northwest of Barrow. In this air mass the measured values of aerosol scattering extinction, and the concentrations of condensation nuclei, aerosol black carbon and SO2 were significantly higher than background in layers from 1 to 5 km. Trajectories arriving at 1.8 and 5 km show the haze to have originated as a polluted air mass over Europe 8 days earlier. On 8 April, while the aircraft sampled over the ice-covered Beaufort Sea, the concentration of haze constituents was found to be significantly less than on the first flight. The trajectories to this region indicate that the air had been over the Arctic Basin and northern Canada for the previous week. On the second flight to Barrow, 9�10 April, concentrations of the pollution constituents had decreased further, and only a shallow layer of elevated aerosol scattering extinction values were observed at 1 km. Trajectory analysis indicates that this haze originated over Europe 2 weeks earlier and found its way to Alaska by way of Svalbard and the Greenland Sea. During the 2�3 April flight trajectories at 290 and 300 K passed over south-central Alaska at about the time of the eruption of the Augustine volcano. An increase in aerosol concentrations and a high value of SO2 immediately below the tropopause over Barrow suggest the presence of volcanic debris. The 290 K trajectory on 8 April also passed downwind of the Augustine volcano while it was erupting, but there was no evidence of debris in that case. Source regions are considered to be at least 1000 km square to be consistent with known uncertainties in trajectory analysis.
Herbert, G.A., R. C. Schnell, H.A. Bridgman, B.A. Bodhaine, S. J. Oltmans and G.E. Shaw, (1989), Meteorology and haze structure during AGASP-II, Part 1: Alaskan Arctic flights, 2-10 April 1986, Journal of Atmospheric Chemistry, 9, 1-3, 17-48, 10.1007/BF00052823 Abstract The second Arctic Gas and Aerosol Sampling Program (AGASP-II) was conducted across the Alaskan and Canadian Arctic in April 1986, to study the in situ aerosol, and the chemical and optical properties of Arctic haze. The NOAA WP-3D aircraft, with special instrumentation added, made six flights during AGASP-II. Measurements of wind, pressure, temperature, ozone, water vapor, condensation nuclei (CN) concentration, and aerosol scattering extinction (bsp) were used to determine the location of significant haze layers. The measurements made on the first three flights, over the Arctic Ocean north of Barrow and over the Beaufort Sea north of Barter Island, Alaska are discussed in detail in this report of the first phase of AGASP II. In the Alaskan Arctic the WP-3D detected a large and persistent region of haze between 960 and 750 mb, in a thermally stable layer, on 2, 8, and 9 April 1986. At its most dense, the haze contained CN concentrations >10,000 cm�3 and bsp of 80�10�6 m�1 suggesting active SO2 to H2SO4 gas-to-particle conversion. Calculations based upon observed SO2 concentrations and ambient relative humidities suggest that 104�105 small H2SO4 droplets could have been produced in the haze layers. High concentrations of sub-micron H2SO4 droplets were collected in haze. Ozone concentrations were 5�10 ppb higher in the haze layers than in the surrounding troposphere. Outside the regions of haze, CN concentrations ranged from 100 to 400 cm�3 and bsp values were about (20�40)�10�6 m�1. Air mass trajectories were computed to depict the air flow upwind of regions in which haze was observed. In two cases the back trajectories and ground measurements suggested the source to be in central Europe.
Hirdman, D, H Sodemann, S Eckhardt, J Burkhart, A. Jefferson, T. Mefford, P Quinn, S Sharma, J Strom and A Stohl, (2010), Source identification of short-lived air pollutants in the Arctic using statistical analysis of measurement data and particle dispersion model output, Atmospheric Chemistry and Physics, 10, , 10.5194/acp-10-669-2010 Abstract As a part of the IPY project POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate Chemistry, Aerosols and Transport), this paper studies the sources of equivalent black carbon (EBC), sulphate, light-scattering aerosols and ozone measured at the Arctic stations Zeppelin, Alert, Barrow and Summit during the years 2000�2007. These species are important pollutants and climate forcing agents, and sulphate and EBC are main components of Arctic haze. To determine where these substances originate, the measurement data were combined with calculations using FLEXPART, a Lagrangian particle dispersion model. The climatology of atmospheric transport from surrounding regions on a twenty-day time scale modelled by FLEXPART shows that the stations Zeppelin, Alert and Barrow are highly sensitive to surface emissions in the Arctic and to emissions in high-latitude Eurasia in winter. Emission sensitivities over southern Asia and southern North America are small throughout the year. The high-altitude station Summit is an order of magnitude less sensitive to surface emissions in the Arctic whereas emissions in the southern parts of the Northern Hemisphere continents are more influential relative to the other stations. Our results show that for EBC and sulphate measured at Zeppelin, Alert and Barrow, northern Eurasia is the dominant source region. For sulphate, Eastern Europe and the metal smelting industry in Norilsk are particularly important. For EBC, boreal forest fires also contribute in summer. No evidence for any substantial contribution to EBC from sources in southern Asia is found. European air masses are associated with low ozone concentrations in winter due to titration by nitric oxides, but are associated with high ozone concentrations in summer due to photochemical ozone formation. There is also a strong influence of ozone depletion events in the Arctic boundary layer on measured ozone concentrations in spring and summer. These results will be useful for developing emission reduction strategies for the Arctic.
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Jaffe, D.A., R.E. Honrath, D. Furness, T. J. Conway, E. J. Dlugokencky and L. P. Steele, (1995), A determination of the CH4, NOx and CO2 emissions from the Prudhoe Bay, Alaska oil development, Journal of Atmospheric Chemistry, 20, 3, 213-227, doi:10.1007/BF00694494 Abstract In this paper we quantify the CH4, CO2 and NO x emissions during routine operations at a major oil and gas production facility, Prudhoe Bay, Alaska, using the concentrations of combustion by products measured at the NOAA-CMDL observatory at Barrow, Alaska and fuel consumption data from Prudhoe Bay. During the 1989 and 1990 measurement campaigns, 10 periods (called lsquoeventsrsquo) were unambiguously identified where surface winds carry the Prudhoe Bay emissions to Barrow (approximately 300 km). The events ranged in duration from 8�48 h and bring ambient air masses containing substantially elevated concentrations of CH4, CO2 and NO y to Barrow. Using the slope of the observed CH4 vs CO2 concentrations during the events and the CO2 emissions based on reported fuel consumption data, we calculate annual CH4 emissions of (24+/�8)�103 metric tons from the facility. In a similar manner, the annual NO x emissions are calculated to be (12+/�4)�103 metric tons, which is in agreement with an independently determined value. The calculated CH4 emissions represent the amount released during routine operations including leakage. However this quantity would not include CH4 released during non-routine operations, such as from venting or gas flaring.
Jiang, X., W.L. Ku, R. Shia, Q. Li, J. W. Elkins, R.G. Prinn and Y.L. Yung, (2007), Seasonal cycle of N2O: Analysis of data, Global Biogeochemical Cycles, 21, GB1006, , 10.1029/2006GB002691 Abstract [1] We carried out a systematic study of the seasonal cycle and its latitudinal variation in the nitrous oxide (N2O) data collected by National Oceanic and Atmospheric Administration - Global Monitoring Division (NOAA-GMD) and the Advanced Global Atmospheric Gases Experiment (AGAGE). In order to confirm the weak seasonal signal in the observations, we applied the multitaper method for the spectrum analysis and studied the stations with significant seasonal cycle. In addition, the measurement errors must be small compared with the seasonal cycle. The N2O seasonal cycles from seven stations satisfied these criteria and were analyzed in detail. The stations are Alert (82 degrees N, 62 degrees W), Barrow (71 degrees N, 157 degrees W), Mace Head (53 degrees N, 10 degrees W), Cape Kumukahi (19 degrees N, 155 degrees W), Cape Matatula (14 degrees S, 171 degrees W), Cape Grim (41 degrees S, 145 degrees E) and South Pole (90 degrees S, 102 degrees W). The amplitude ( peak to peak) of the seasonal cycle of N2O varies from 0.29 ppb (parts-per-billion by mole fraction in dry air) at the South Pole to 1.15 ppb at Alert. The month at which the seasonal cycle is at a minimum varies monotonically from April ( South Pole) to September ( Alert). The seasonal cycle in the Northern Hemisphere shows the influence of the stratosphere; the seasonal cycle of N2O in the Southern Hemisphere suggests greater influence from surface sources. Preliminary estimates are obtained for the magnitude of the seasonally varying sources needed to account for the observations.
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Karion, A., C. Sweeney, S. Wolter, T. Newberger, H. Chen, A. Andrews, J. Kofler, D. Neff and P. Tans, (2012), Long-term greenhouse gas measurements from aircraft, Atmospheric Measurement Techniques Discussions, 5, 5, , 10.5194/amtd-5-7341-2012 Abstract In March 2009 the NOAA/ESRL/GMD Carbon Cycle and Greenhouse Gases Group collaborated with the US Coast Guard (USCG) to establish the Alaska Coast Guard (ACG) sampling site, a unique addition to NOAA's atmospheric monitoring network. This collaboration takes advantage of USCG bi-weekly Arctic Domain Awareness (ADA) flights, conducted with Hercules C-130 aircraft from March to November each year. NOAA has installed window-replacement inlet plates on two USCG C-130 aircraft and deploys a pallet with NOAA instrumentation on each ADA flight. Flights typically last 8 h and cover a very large area, traveling from Kodiak, AK in the south up to Barrow, AK in the north, and making altitude profiles near the coast as well as in the interior. NOAA instrumentation on each flight includes: a flask sampling system, a continuous CO₂/CH₄/CO/H₂O analyzer, a continuous ozone analyzer, and an ambient temperature and humidity sensor. GPS time and location from the aircraft's navigation system are also collected. Air samples collected in flight are analyzed at NOAA/ESRL for the major greenhouse gases and a variety of halocarbons and hydrocarbons that influence climate, stratospheric ozone, and air quality. Instruments on this aircraft are designed and deployed to be able to collect air samples and data autonomously, so that NOAA personnel visit the site only for installation at the beginning of each season. We present an assessment of the cavity ring-down spectroscopy (CRDS) CO₂/CH₄/CO/H₂O analyzer performance operating on an aircraft over a three-year period. We describe the overall system for making accurate greenhouse gas measurements using a CRDS analyzer on an aircraft with minimal operator interaction. Short and long-term stability of the CRDS analyzer over a seven-month deployment period is better than 0.15 ppm, 2 ppb, and 5 ppb for CO₂, CH₄, CO respectively, considering differences of on-board reference tank measurements from a laboratory calibration performed prior to deployment. This stability is not affected by variation in pressure or temperature during flight. Biases and standard deviations of comparisons with flask samples suggest that atmospheric variability, flask-to-flask variability, and possible flask sampling biases may be driving biases in the comparison between flasks and in-situ CRDS measurements.
Kasischke, E. S. and L. M. P. Bruhwiler, (2002), Emissions of carbon dioxide, carbon monoxide, and methane from boreal forest fires in 1998, Journal of Geophysical Research-Atmospheres, 108, d1, 8146, doi:10.1029/2001JD000461 Abstract The global boreal forest region experienced some 17.9 million ha of fire in 1998, which could be the highest level of the decade. Through the analysis of fire statistics from North America and satellite data from Russia, semimonthly estimates of area burned for five different regions in the boreal forest were generated and used to estimate total carbon release and CO2, CO, and CH4 emissions. Different levels of biomass, as well as different biomass categories, were considered for each of the five different regions (including peatlands in the Russian Far East and steppes in Siberia), as were different levels of fraction of biomass (carbon) consumed during fires. Finally, two levels of flaming versus smoldering combustion were considered in the model. Boreal forest fire emissions for 1998 were estimated to be 290�383 Tg of total carbon, 828�1103 Tg of CO2, 88�128 Tg of CO, and 2.9�4.7 Tg of CH4. The higher estimate represents 8.9% of total global carbon emissions from biomass burning, 13.8% of global fire CO emissions, and 12.4% of global fire CH4 emissions. Russian fires accounted for 71% of the total emissions, with the remainder (29%) from fires in North America. Assumptions regarding the level of smoldering versus flaming generally resulted in small (<4%) variations into the emissions estimates, although in two cases, these variations were higher (6% and 12%). We estimated that peatland fires in the Russian Far East contributed up to 40 Tg of carbon to the atmosphere in the fall of 1998. The combined seasonal CO emissions from forest and peatland fires in Russia are consistent with anomalously high atmospheric CO measurements collected at Point Barrow, Alaska.
Kiedron, P., J. Michalsky, B. Schmid, D. Slater, J. Berndt, L. Harrison, P. Racette, E. Westwater and Y. Han, (2001), A robust Retrieval of Water Vapor Column in Dry Arctic Conditions Using the Rotating Shadowband Spectroradiometer, Journal of Geophysical Research Atmospheres, 106, D20, 24007-24016, Abstract A method to retrieve water vapor column using the 940-nm water vapor absorption band in dry Arctic conditions is presented. The retrievals with this method are stable with respect to uncertainties in instrument radiometric calibration, air pressure, solar source function, and aerosols. The water vapor column was retrieved with this method using spectra obtained with the rotating shadowband spectroradiometer (RSS) that was deployed during an intensive observation period near Barrow, Alaska, in March 1999. A line-by-line radiative transfer model was used to compute water vapor transmittance. The retrievals with this method are compared with retrievals obtained from three independent measurements with microwave radiometers. All four measurements show the same pattern of temporal variations. The RSS results agree most closely with retrievals obtained with the millimeter-wave imaging radiometer (MIR) at its 183 GHz � 7 double-side band channel. Their correlation over a period of 7 days when water vapor column varied between 0.75 mm and 3.6 mm (according to RSS) is 0.968 with MIR readings 0.12 mm higher on average.
Komhyr, W. D., (1983), An aerosol and gas sampling apparatus for remote observatory use, Journal of Geophysical Research, 88, C6, 3913-3918, 10.1029/JC088iC06p03913 Abstract An air sampling apparatus is described which standardizes sampling height at a field station at 10 m or more above ground level and which minimizes loss of particles and destruction and contamination of sampled trace atmospheric gases as air is conducted through the apparatus to various monitoring instruments. Basic design features render the apparatus useful for air sampling under widely varying climate conditions, and at station altitudes ranging from sea level to more than 4 km. Four systems have been built, and have been used sucessfully since 1977 at the NOAA Geophysical Monitoring for Climatic Change program baseline stations at Point Barrow, Alaska; Mauna Loa, Hawaii; American Samoa, South Pacific; and South Pole, Antarctica.
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Lanconelli, C., M. Busetto, E. G. Dutton, G. K�nig, M. Maturilli, R. Sieger, V. Vitale and T. Yamanouchi, (2011), Polar baseline surface radiation measurements during the International Polar Year 2007-2009, Earth System Science Data, 3, 1, 1-8, doi:10.5194/essd-3-1-2011 Abstract Downwelling and upwelling shortwave and longwave radiation components from six active polar sites, taking part of the Baseline Surface Radiation Network (BSRN), were selected for the period of the last International Polar Year (March 2007 to March 2009), and included in the BSRN-IPY dataset, along with metadata and supplementary data for some of the stations. Two sites, located at Svalbard archipelago (Ny �lesund) and Alaska (Barrow), represent Arctic sea-level conditions. Four Antarctic stations represent both sea-level (Dronning Maud Land and Cosmonaut Sea) and high-elevation conditions (South Pole and East Antarctic Plateau). The BSRN-IPY dataset content and quality are discussed. The dataset is now available at doi:10.1594/PANGAEA.737668, and can be used for free after accepting the BSRN data release guidelines. The dataset has been summarized as monthly averages and subject to further evaluation according to strict criteria not previously applied.
Li, S.-M., J.W. Winchester, J.D. Kahl, S. J. Oltmans, R. C. Schnell and P. J. Sheridan, (1990), Arctic Boundary Layer Ozone Variations Associated With Nitrate, Bromine, and Meteorology: A Case Study, Journal of Geophysical Research-Atmospheres, 95, D13, 22433-22440, 90JD01947 Abstract Gas and aerosol measurements at Barrow, Alaska during the spring of 1986 confirm the inverse relationship between particulate excess bromine (xBr) and O3. In addition to this inverse XBr�O3 relationship, several other factors were found to be important in understanding the springtime variability of O3 at Barrow. They are (1) O3 concentration variability associated with NOx chemistry at high pollutant levels or transport of primary pollutant O3 from lower latitudes, (2) displacement of air masses of high O3 content with air masses low in O3 but high in sea salt, suggesting potential roles of sea salt in O3 fluctuations, and (3) when pollutant levels were low, advection of air that can cause gradual change in O3 with more rapid inversely related fluctuations of O3 and xBr superimposed. Under the conditions of factor 3 the trend and anticorrelation each accounted for about one quarter of the variance in O3, suggesting a role for other compounds or low level reactive nitrogen species and gas-particle interaction in the photolytic O3 destruction process.
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Marty, C., R. Philipona, J. Delamere, E. G. Dutton, J. J. Michalsky, K. Stamnes, R. Storvold, T. Stoffel, S. A. Clough and E. J. Mlawer, (2003), Downward longwave irradiance uncertainty under arctic atmospheres: Measurements and modeling, Journal of Geophysical Research-Atmospheres, 108, d12, 4-1, doi:10.1029/2002JD002937 Abstract [1] Measurement and modeling of downward longwave irradiance are a special challenge in arctic winter due to its low water vapor content and the extreme meteorological conditions. There are questions about the representativeness of the instrument calibration, the consistency and uncertainty of measurements and models in these environments. The Second International Pyrgeometer and Absolute Sky-scanning Radiometer Comparison (IPASRC-II), which was conducted at Atmospheric Radiation Measurement (ARM) program�s North Slope of Alaska (NSA) site in Barrow provided a unique opportunity to compare high accuracy downward longwave irradiance measurements and radiative transfer model computations during arctic winter. Participants from 11 international institutions deployed 14 pyrgeometers, which were field-calibrated against the Absolute Sky-scanning Radiometer (ASR). Continuous measurements over a 10-day period in early March 2001 with frequent clear-sky conditions yielded downward longwave irradiances between 120 and 240 W m2. The small average difference between ASR irradiances, pyrgeometer measurements, MODTRAN and LBLRTM radiative transfer computations indicates that the absolute uncertainty of measured downward longwave irradiance under arctic winter conditions is within �2 W m2.
Miller, J. B., K.A. Mack, R. Dissly, J.W.C. White, E. J. Dlugokencky and P. P. Tans, (2002), Development of analytical methods and measurements of 13C/12C in atmospheric CH4 from the NOAA Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network, Journal of Geophysical Research-Atmospheres, 107, d13, 4178, doi:10.1029/2001JD000630 Abstract We describe the development of an automated gas chromatography-isotope ratio mass spectrometry (GC-IRMS) system capable of measuring the carbon isotopic composition of atmospheric methane (?13CH4) with a precision of better than 0.1�. The system requires 200 mL of air and completes a single analysis in 15 min. The combination of small sample size, fast analysis time, and high precision has allowed us to measure background variations in atmospheric ?13CH4 through the NOAA Climate Monitoring and Diagnostics Laboratory Cooperative Air Sampling Network. We then present a record of ?13CH4 obtained from six surface sites of the network between January 1998 and December 1999. The sites are Barrow, Alaska (71�N); Niwot Ridge, Colorado (40�N); Mauna Loa, Hawaii (20�N); American Samoa (14�S); Cape Grim, Tasmania (41�S); and the South Pole (90�S). For the years 1998 and 1999, the globally averaged surface ?13C value was ?47.1�, and the average difference between Barrow and the South Pole was 0.6�. Consistent seasonal variations were seen only in the Northern Hemisphere, especially at Barrow, where the average amplitude was 0.5�. Seasonal variations in 1998, however, were evident at all sites, the cause of which is unknown. We also use a two-box model to examine the extent to which annual average ?13C and CH4 mole fraction measurements can constrain broad categories of source emissions. We find that the biggest sources of error are not the atmospheric ?13C measurements but instead the radiocarbon-derived fossil fuel emission estimates, rate coefficients for methane destruction, and isotopic ratios of source emissions.
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Novelli, P. C., L. P. Steele and P. P. Tans, (1992), Mixing Ratios of Carbon Monoxide in the Troposphere, Journal of Geophysical Research-Atmospheres, 97, D18, 20731-20750, JD02010 Abstract Carbon monoxide (CO) mixing ratios were measured in air samples collected weekly at eight locations. The air was collected as part of the CMDL/NOAA cooperative flask sampling program (Climate Monitoring and Diagnostics Laboratory, formerly Geophysical Monitoring for Climatic Change, Air Resources Laboratory/National Oceanic and Atmospheric Administration) at Point Barrow, Alaska (71�N), Niwot Ridge, Colorado (40�N), Mauna Loa and Cape Kumakahi, Hawaii (19�N), Guam, Marianas Islands (13�N), Christmas Island (2�N), Ascension Island (8�S) and American Samoa (14�S). Half-liter or 3-L glass flasks fitted with glass piston stopcocks holding teflon O rings were used for sample collection. CO levels were determined within several weeks of collection using gas chromatography followed by mercuric oxide reduction detection, and mixing ratios were referenced against the CMDL/NOAA carbon monoxide standard scale. During the period of study (mid-1988 through December 1990) CO levels were greatest in the high latitudes of the northern hemisphere (mean mixing ratio from January 1989 to December 1990 at Point Barrow was approximately 154 ppb) and decreased towards the south (mean mixing ratio at Samoa over a similar period was 65 ppb). Mixing ratios varied seasonally, the amplitude of the seasonal cycle was greatest in the north and decreased to the south. Carbon monoxide levels were affected by both local and regional scale processes. The difference in CO levels between northern and southern latitudes also varied seasonally. The greatest difference in CO mixing ratios between Barrow and Samoa was observed during the northern winter (about 150 ppb). The smallest difference, 40 ppb, occurred during the austral winter. The annually averaged CO difference between 71�N and 14�S was approximately 90 ppb in both 1989 and 1990; the annually averaged interhemispheric gradient from 71�N to 41�S is estimated as approximately 95 ppb.
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Oltmans, S. J., A.S. Lefohn, J. M. Harris, D.W. Tarasick, A.M. Thompson, H. Wernli, B. J. Johnson, P. C. Novelli, S. A. Montzka, J.D. Ray, L. Patrick, C. Sweeney, A. Jefferson, T. Dann, J. Davies, I. Shapiro and B.N. Holben, (2010), Enhanced ozone over western North America from biomass burning in Eurasia during April 2008 as seen in surface and profile observations, Atmospheric Environment, 44, 35, 4497-4509, doi:10.1016/j.atmosenv.2010.07.004 Abstract During April 2008, as part of the International Polar Year (IPY), a number of ground-based and aircraft campaigns were carried out in the North American Arctic region (e.g., ARCTAS, ARCPAC). The widespread presence during this period of biomass burning effluent, both gaseous and particulate, has been reported. Unusually high ozone readings for this time of year were recorded at surface ozone monitoring sites from northern Alaska to northern California. At Barrow, Alaska, the northernmost point in the United States, the highest April ozone readings recorded at the surface (hourly average values >55 ppbv) in 37 years of observation were measured on April 19, 2008. At Denali National Park in central Alaska, an hourly average of 79 ppbv was recorded during an 8-h period in which the average was over 75 ppbv, exceeding the ozone ambient air quality standard threshold value in the U.S. Elevated ozone (>60 ppbv) persisted almost continuously from April 19�23 at the monitoring site during this event. At a coastal site in northern California (Trinidad Head), hourly ozone readings were >50 ppbv almost continuously for a 35-h period from April 18�20. At several sites in northern California, located to the east of Trinidad Head, numerous occurrences of ozone readings exceeding 60 ppbv were recorded during April 2008. Ozone profiles from an extensive series of balloon soundings showed lower tropospheric features at 1�6 km with enhanced ozone during the times of elevated ozone amounts at surface sites in western Canada and the U.S. Based on extensive trajectory calculations, biomass burning in regions of southern Russia was identified as the likely source of the observed ozone enhancements. Ancillary measurements of atmospheric constituents and optical properties (aerosol optical thickness) supported the presence of a burning plume at several locations. At two coastal sites (Trinidad Head and Vancouver Island), profiles of a large suite of gases were measured from airborne flask samples taken during probable encounters with burning plumes. These profiles aided in characterizing the vertical thickness of the plumes, as well as confirming that the plumes reaching the west coast of North America were associated with biomass burning events.
Oltmans, S. J., A. S Lefohn, J. M. Harris, D. W. Tarasick, A. M Thompson and H. Wernli, (2010), Enhanced ozone over western North America from biomass burning in Eurasia during April 2008 as seen in surface and profile observations, State of the Arctic, 16 - 19 March, Miami Florida Abstract During April 2008 as part of the International Polar Year, a number of ground-based and aircraft campaigns were carried out in the North American arctic region. The ubiquitous presence during this period of biomass burning effluent, both gaseous and particulate, has been reported. Unusually high ozone readings for this time of year were recorded at surface ozone monitoring sites from northern Alaska to northern California. At Barrow, Alaska the highest April ozone readings recorded at the surface (hourly average values >55 ppbv) in 36 years of observation were measured on April 19, 2008. At Denali National Park in central Alaska an hourly average of 79 ppbv was recorded during an 8 hour period in which the average was over 75 ppb, exceeding the ozone ambient air standard threshold value in the U.S.. Elevated ozone (>60 ppbv) persisted almost continuously from April 19�23 at the monitoring site as part of this event. During the first three weeks of April 2008, near daily ozone soundings were performed at several sites in western North America as part of the Arctic Intensive Ozonesonde Network Study (ARCIONS) in conjunction with ARCTAS. These soundings showed lower tropospheric features at ~1-6 km with enhanced ozone during the times of elevated ozone amounts at the surface sites noted above. Ancillary information, such as aerosol optical thickness and back trajectories, are employed to diagnose the potential air masses that may have contributed to these elevated ozone readings. The back trajectories appear to be matched with known burning source regions in the Eurasian region during April 2008. At a few surface sites, atmospheric trace constituents in addition to ozone were measured that help identify biomass burning as a likely source of the enhanced ozone readings.
Oltmans, S. J., B. J. Johnson and J. M. Harris, (2012), Springtime boundary layer ozone depletion at Barrow, Alaska: Meteorological influence, year-to-year variation, and long-term change, Journal of Geophysical Research, 117, D00R18, 10.1029/2011JD016889 Abstract In April 2008 and March-April 2009 near daily ozonesonde measurements were made over a several week period to study springtime Arctic boundary layer ozone loss in the vicinity of Barrow, Alaska. A detailed picture of the vertical structure of the depletion events from the soundings was obtained showing that the depletion was confined to approximately the lowest 1000 m with an average height of the top of the layer at $500 m. The two years were strongly contrasting in the frequency of ozone depletion events providing an opportunity for investigating the differing conditions under which these events develop. Short-term variability of the ozone depletion events is closely tied to the frequency of airflow that is primarily Arctic Ocean in origin (more depletion) or originates at lower latitudes (less depletion). The ubiquitous depletion events are interrupted by periodic mixing of ozone rich air into the boundary layer with the onset of synoptic scale weather changes that interrupt flow from off the Arctic Ocean. A 38-year record of surface ozone measurements at Barrow provides a unique time series that reveals the strong year-to-year variability of ozone depletion event occurrence. During March, but not April or May, there has been a significant increase in the frequency of ozone depletion events. This long-term increase in March depletion events appears to follow the decline in multiyear sea ice in the Arctic Ocean and its replacement by first-year ice. This significant change in the occurrence of boundary layer ozone events in March may signal a change in the oxidative chemistry in the Arctic that is related to climate change in this sensitive region.
Oltmans, S. J., R. C. Schnell, P. J. Sheridan, R. E. Peterson, S. -M. Li, J. W. Winchester, P. P. Tans, W. T. Sturges, J. D. Kahl and L. A. Barrie, (1989), Seasonal surface ozone and filterable bromine relationship in the high Arctic, Atmospheric Environment, 23, 11, 2431-2441, 10.1016/0004-6981(89)90254-0 Abstract Ozone and filterable bromine measurements in the high Arctic during the spring return of solar radiation suggest a rapid concurrent destruction of O3 and conversion of gaseous to particulate Br. Multiyear observations show that this pattern is an annual feature of O3 measured near the surface at Barrow, Alaska, and other Arctic locations. Aircraft measurements show low O3 amounts and high filterable Br concentrations beneath the surface temperature inversion over ice throughout the Arctic in the spring. A wintertime build-up of the gaseous organic compound bromoform and a rapid depletion of bromoform in the spring may be a link between the episodic O3 depletion events and the accompanying rise in filterable Br.
Oltmans, S. J. and H. I. Levy, (1994), Surface ozone measurements from a global network, Atmospheric Environment, 28, 1, 9-24, doi:10.1016/1352-2310(94)90019-1 Abstract From a network of sites, primarily in the Atlantic and Pacific Ocean regions, measurements of the surface ozone concentration yield information on the seasonal, synoptic, and diurnal patterns. These sites, generally removed from the effects of local pollution sources, show characteristics that typify broad geographical regions. At Barrow, AK; Mauna Loa, HI; American Samoa; and South Pole, data records of 15�20 years show trends that in all cases are a function of season. This dependence on season is important in understanding the causes of the long-term changes. At Barrow, the summer (July, August, September) increase of 1.7% per year is probably indicative of photochemical production. At South Pole, on the other hand, the summer (December, January, February) decrease is related to photochemical losses and enhanced transport from the coast of Antarctica. At all the sites there is a pronounced seasonal variation. In the Southern Hemisphere (SH), all locations which run from 14 to 90�S show a winter (July� August) maximum and summer minimum. In the Northern Hemisphere (NH) most of the sites show a spring maximum and autumn minimum. At Barrow (70�N) and Barbados (14�), however, the maxima occur during the winter, but for very different reasons. At many of the sites, the transport changes associated with synoptic scale weather patterns dominate the day-to-day variability. This is particularly pronounced at Bermuda and the more tropical sites. In the tropics, there is a very regular diurnal surface ozone cycle with minimum values in the afternoon maxima early in the morning. This appears to result from photochemical destruction during the day in regions with very low concentrations of nitrogen oxides. At Niwot Ridge, CO, and Mace Head, Ireland, there is clear evidence of photochemical ozone production in the summer during transport from known regional pollution sources.
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Peterson, J.T., K.J. Hanson, B.A. Bodhaine and S. J. Oltmans, (1980), Dependence of CO2, aerosol, and ozone concentrations on wind direction at Barrow, Alaska during winter, Geophysical Research Letters, 7, 5, 349-352, doi:10.1029/GL007i005p00349 Abstract Measurements of CO2, aerosol scattering, condensation nuclei, and ozone made continuously at the NOAA baseline observatory at Barrow, Alaska, have been analyzed in conjunction with low?level trajectories of airflow arriving at Barrow during periods from January to March of 1977 and 1978. Ozone concentrations had no dependence on wind direction whereas CO2 and aerosol values did show directional dependence; higher values occurred with airflow from the Arctic Basin than with that from the south. The aerosol analyses support the hypothesis that Arctic haze results from advection of aerosols to the Arctic from European or North American anthropogenic sources. CO2 results suggest two possible sources for the higher concentrations: transfer from the ocean through annual sea ice to the Arctic atmosphere or advection from mid?latitude anthropogenic sources similar to that for the Arctic haze.
Peterson, J. T., W.D. Komhyr, L.S. Waterman, R.H. Gammon, K. W. Thoning and T. J. Conway, (1989), Atmospheric CO2 variations at Barrow, Alaska, 1973-1982, Journal of Atmospheric Chemistry, 4, 4, 491-510, 10.1007/BF00053848 Abstract The first 10 years (1973-1982) of atmospheric CO2 measurements at Barrow, Alaska, by the NOAA/GMCC program are described. The paper updates and extends the Barrow CO2 record presented in Tellus (1982). The data are given in final form, based on recent calibrations of the Scripps Institution of Oceanography, with selected values identified as representative of large, spacescale conditions. Analyses of the data show: (1) a long-term CO2 average increase of 1.3 ppm per year, but with large year-to-year variations in that growth rate; (2) a suggestion, not statistically significant, of a secular increase in the amplitude of the annual cycle, presumably a reflection of global-scale biospheric variability; and (3) good absolute agreement between the Barrow results and those from four neighboring high latitude sites between 50 and 82°N.
Polissar, A. V., P. K. Hopke, P. Paatero, Y. J. Kaufmann, D. K. Hall, B. A. Bodhaine, E. G. Dutton and J. M. Harris, (1999), The aerosol at Barrow, Alaska: long-term trends and source locations, Atmospheric Environment, 33, 16, 2441-2458, Abstract Aerosol data consisting of condensation nuclei (CN) counts, black carbon (BC) mass, aerosol light scattering (SC), and aerosol optical depth (AOD) measured at Barrow, Alaska from 1977 to 1994 have been analyzed by three-way positive matrix factorization (PMF3) by pooling all of the di!erent data into one large three-way array. The PMF3 analysis identi"ed four factors that indicate four di!erent combinations of aerosol sources active throughout the year in Alaska. Two of the factors (F1, F2) represent Arctic haze. The "rst Arctic haze have factor F1 is dominant in January}February while the second factor F2 is dominant in March}April. They appear to be material that is generally ascribed to long-range transported anthropogenic particles. A lower ratio of condensation nuclei to scattering coe$cient loadings is obtained for F2 indicating larger particles. Factor F3 is related to condensation nuclei. It has an annual cycle with two maxima, March and July}August indicating some involvement of marine biogenic sources. The fourth factor F4 represents the contribution to the stratospheric aerosol from the eruptions of El Chichon and Mt. Pinatubo. No signi"cant long-term trend for F1 was detected while F2 shows a negative trend over the period from 1982 to 1994 but not over the whole measurement period. A positive trend of F3 over the whole period has been observed. This trend may be related to increased biogenic sulfur production caused by reductions in the sea-ice cover in the Arctic and/or an air temperature increase in the vicinity of Barrow. Potential source contribution function (PSCF) analysis showed that in winter and spring during 1989 to 1993 regions in Eurasia and North America are the sources of particles measured at barrow. In contrast to this, large areas in the North Paci"c Ocean and the Arctic Ocean was contributed to observed high concentrations of CN in the summer season. Three-way positive matrix factorization was an e!ective method to extract time-series information contained in the measured quantities. PSCF was useful for the identi"cation possible source areas and the potential pathways for the Barrow aerosol. The e!ects of long-distance transport, photochemical aerosol production, emissions from biogenic activities in the ocean, volcanic eruptions on the aerosol measurements made at Barrow were extracted using this combined methodology.
Polissar, A. V., P. K. Hopke and J. M. Harris, (2001), Source Regions for Atmospheric Aerosol Measured at Barrow, Alaska, Environmental Science and Technology, 35, 21, 4214-4226, 10.1021/es0107529 Abstract Aerosol data consisting of condensation nuclei (CN) counts, black carbon (BC) mass concentration, and aerosol light scattering coefficient at the wavelength of 450 nm (SC) measured at Barrow, AK, from 1986 to 1997 have been analyzed. BC and SC show an annual cycle with the Arctic haze maxima in the winter and spring and the minima in the summer. The CN time series shows two maxima in March and August. Potential source contribution function (PSCF) that combines the aerosol data with air parcel backward trajectories was applied to identify potential source areas and the preferred pathways that give rise to the observed high aerosol concentrations at Barrow. Ten-day isentropic back trajectories arriving twice daily at 500 and 1500 m above sea level were calculated for the period from 1986 to 1997. The PSCF analyses were performed based on the 80th percentile criterion values for the 2- and 24-h averages of the measured aerosol parameters. There was a good correspondence between PSCF maps for the 2- and 24-h averages, indicating that 1-day aerosol sampling in the Arctic adequately represents the aerosol source areas. In winter, the high PSCF values for BC and SC are related to industrial source areas in Eurasia. The trajectory domain in winter and spring is larger than in summer, reflecting weaker transport in summer. No high PSCF areas for BC and SC can be observed in summer. The result is related to the poor transport into the Arctic plus the strong removal of aerosol by precipitation in summer. In contrast to the BC and SC maps, the CN plot for summer shows high PSCF areas in the North Pacific Ocean. High CN values appear to be mostly connected with the long-range transport from Eurasia in winter and spring and with the reduced sulfur compound emission from biogenic activities in the ocean in the summer. PSCF analysis was found to be effective in identifying potential aerosol source areas.
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Quay, P., J. Stutsman, D. Wilbur, A. Snover, E. J. Dlugokencky and T. Brown, (1999), The Isotopic Composition of Atmospheric Methane, Global Biogeochemical Cycles, 13, 2, 445-461, 1998GB900006 Abstract Measurements of the 13C/12C, D/H and 14C composition of atmospheric methane (CH4) between 1988 and 1995 are presented. The 13C/12C measurements represent the first global data set with time series records presented for Point Barrow, Alaska (71�N), Olympic Peninsula, Washington (48�N), Mauna Loa, Hawaii (20�N), American Samoa (14�S), Cape Grim, Australia (41�S), and Baring Head, New Zealand (41�S). North-south trends of the 13C/12C and D/H of atmospheric CH4 from air samples collected during oceanographic research cruises in the Pacific Ocean are also presented. The mean annual ?13C increased southward from about ?47.7 � at 71�N to ?41.2 � at 41�S. The amplitude of the seasonal cycle in ?13C ranged from about 0.4 � at 71�N to 0.1 � at 14�S. The seasonal ?13C cycle at sites in tropical latitudes could be explained by CH4 loss via reaction with OH radical, whereas at temperate and polar latitudes in the northern hemisphere seasonal changes in the ?13C of the CH4 source were needed to explain the seasonal cycle. The higher ?13C value in the southern (?47.2 �) versus northern (?47.4 �) hemisphere was a result of interhemispheric transport of CH4. A slight interannual ?13C increase of 0.02�0.005 � yr?1 was measured at all sites between 1990 and 1995. The mean ?D of atmospheric CH4 was ?86�3 � between 1989 and 1995 with a 10 � depletion in the northern versus southern hemisphere. The 14C content of CH4 measured at 48�N increased from 122 to 128 percent modern between 1987 and 1995. The proportion of CH4 released from fossil sources was 18�9% in the early 1990s as derived from the 14C content of CH4.
Quinn, P. K., G. Shaw, E. Andrews, E. G. Dutton, T. Ruoho-Airola and S. L. Gong, (2007), Arctic Haze: Current trends and knowledge gaps, Tellus. Series B, 59, 99-114, 10.1111/j.1600-0889.2006.00238.x Abstract Trend analyses were performed on several indicators of Arctic haze using data from sites located in the North American, Norwegian, Finnish and Russian Arctic for the spring months of March and April. Concentrations of nonseasalt (nss) SO4 = in the Canadian, Norwegian and Finnish Arctic were found to have decreased by 30�70% from the early 1990s to present. The magnitude of the decrease depended on location. The trend in nss SO4 = at Barrow, Alaska from 1997 to present, is unclear. Measurements at Barrow of light scattering by aerosols show a decrease of about 50% between the early 1980s and the mid-1990s for both March and April. Restricting the analysis to the more recent period of 1997 to present indicates an increase in scattering of about 50% during March. Aerosol NO3? measured at Alert, Canada has increased by about 50% between the early 1990s and 2003. Nss K+ and light absorption, indicators of forest fires, have a seasonal maximum during the winter and spring and minimum during the summer and fall at both Alert and Barrow. Based on these data, the impact of summertime forest fire emissions on low-altitude surface sites within the Arctic is relatively small compared to winter/spring emissions. Key uncertainties about the impact of long range transport of pollution to the Arctic remain including the certainty of the recent detected trends; sources, transport and trends of soot; and radiative effects due to complex interactions between aerosols, clouds and radiation in the Arctic.
Quinn, P. K., T. L. Miller, T. S. Bates, J. A. Ogren, E. Andrews and G. E. Shaw, (2002), A Three-Year Record of Simultaneously Measured Aerosol Chemical and Optical Properties at Barrow, Alaska, Journal of Geophysical Research Atmospheres, 107, D11, 4130, 10.1029/2001JD001248 Abstract Results are presented from 3 years of simultaneous measurements of aerosol chemical composition and light scattering and absorption at Barrow, Alaska. All results are reported at the measurement relative humidity of 40%. Reported are the annual cycles of the concentration of aerosol mass, sea salt, non-sea-salt (nss) sulfate, methanesulfonate or MSA-, NH4+, and nss K+, Mg+2, and Ca+2 for the submicron and supermicron size ranges. Submicron nss SO4=, NH4+, and nss K+, Mg+2, and Ca+2 peak in winter and early spring corresponding to the arrival and persistence of Arctic Haze. Submicron sea salt displays a similar annual cycle presumably due to long-range transport from the northern Pacific Ocean. Supermicron sea salt peaks in summer corresponding to a decrease in sea ice extent. Submicron and supermicron MSA- peak in the summer due to a seasonal increase in the flux of dimethylsulfide from the ocean to the atmosphere. A correlation of MSA- and particle number concentrations suggests that summertime particle production is associated with this biogenic sulfur. Mass fractions of the dominant chemical species were calculated from the concentrations of aerosol mass and chemical species. For the submicron size range the ionic mass and associated water make up 80 to 90% of the aerosol mass from November to May. Of this ionic mass, sea salt and nss SO4= are the dominant species. The residual mass fraction, or fraction of mass that is chemically unanalyzed, is equivalent to the ionic mass fraction in June through October. For the supermicron size range the ionic mass and associated water make up 60 to 80% of the aerosol mass throughout the year with sea salt being the dominant species. Also reported for the submicron size range are the annual cycles of aerosol light scattering and absorption at 550 nm, �ngstr�m exponent for the 450 and 700 nm wavelength pair, and single scattering albedo at 550 nm. On the basis of linear regressions between the concentrations of sea salt and nss SO4= and the light scattering coefficient, sea salt has a dominant role in controlling light scattering during the winter, nss SO4= is dominant in the spring, and both components contribute to scattering in the summer. Submicron mass scattering efficiencies of the dominant aerosol chemical components (nss SO4=, sea salt, and residual mass) were calculated from a multiple linear regression of the measured light scattering versus the component concentrations. Submicron nss SO4= mass scattering efficiencies were relatively constant throughout the year with seasonal averages ranging from 4.1 � 2.9 to 5.8 � 1.0 m2 g-1. Seasonal averages for submicron sea salt ranged from 1.8 � 0.37 to 5.1 � 0.97 m2 g-1 and for the residual mass ranged from 0.21 � 0.31 to 1.5 � 1.0 m2 g-1. Finally, concentrations of nss SO4= measured at Barrow were compared to those measured at Poker Flat Rocket Range, Denali National Park, and Homer for the 1997/1998 and 1998/1999 Arctic Haze seasons. Concentrations were highest at Barrow and decreased with latitude from Poker Flat to Denali to Homer revealing a north to south gradient in the extent of the haze.
Quinn, P.K., T.S. Bates, T.L. Miller, D.J. Coffman, J.E. Johnson, J. M. Harris, J. A. Ogren, G. Forbes, T.L. Anderson, D.S. Covert and M. J. Rood, (2000), Surface submicron aerosol chemical composition: What fraction is not sulfate?, Journal of Geophysical Research-Atmospheres, 105, D5, 6785-6805, JD901034 Abstract Measurements of submicron aerosol mass and the mass of major ionic components have been made over the past 5 years on cruises in the Pacific and Southern Oceans and at monitoring stations across North America (Barrow, Alaska; Cheeka Peak, Washington; Bondville, Illinois; and Sable Island, Nova Scotia). Reported here are submicron concentrations of aerosol mass, nonsea salt (nss) sulfate, sea salt, methanesulfonate, other nss inorganic ions, and residual, or chemically unanalyzed, mass. Residual mass concentrations are based on the difference between simultaneously measured aerosol mass and the mass of the major ionic components. A standardized sampling protocol was used for all measurements making the data from each location directly comparable. For the Pacific and Southern Oceans, concentrations of the chemical components are presented in zonally averaged 20� latitude bins. For the monitoring stations, mean concentrations are presented for distinct air mass types (marine, clean continental, and polluted based on air mass back trajectories). In addition, percentile information for each chemical component is given to indicate the variability in the measured concentrations. Mean nss sulfate submicron aerosol mass fractions for the different latitude bins of the Pacific ranged from 0.14 � 0.01 to 0.34 � 0.03 (arithmetic mean � absolute uncertainty at the 95% confidence level). The lowest average value occurred in the 40��60�S latitude band where nss sulfate concentrations were low due to the remoteness from continental sources and sea salt concentrations were relatively high. Mean nss sulfate aerosol mass fractions were more variable at the monitoring stations ranging from 0.13 � 0.004 to 0.65 � 0.02. Highest values occurred in polluted air masses at Bondville and Sable Island. Sea salt mean mass fractions ranged between 0.20 � 0.02 and 0.53 � 0.03 at all latitude bands of the Pacific (except 20��40�N where the residual mass fraction was relatively high) and at Barrow. The concentration of residual mass was significant at the 95% confidence level at all stations and all Pacific latitude bands (assuming that all errors were random and normally distributed and contamination of the samples did not occur beyond that accounted for by storage and transport uncertainties). Mean residual mass fractions ranged from 0.09 � 0.07 to 0.74 � 0.04.
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Raatz, W. E., (1985), Meteorological conditions over Eurasia and the Arctic contributing to the March 1983 Arctic haze episode, Atmospheric Environment (1967), 19, 12, 2121-2126, 10.1016/0004-6981(85)90119-2 Abstract It is shown that the 11�18 March 1983 Arctic haze episode observed at Barrow, Alaska, was caused by air pollutants being rapidly transported from Eurasia industrial sources across the Arctic. These sources emitted pollutants into an air mass forming during anticyclonic synoptic conditions. On the basis of potential temperatures observed in the haze layers over Barrow, it is hypothesized that aerosols and gases in the different layers originated from different Eurasian source regions. The Arctic haze episode at Barrow existed as long as there was a meridional large-scale circulation pattern of the Arctic atmosphere and ceased when the circulation became zonal in character.
Rasmussen, R. A., M. A. K. Khalil and R. J. Fox, (1983), Altitudinal and temporal variation of hydrocarbons and other gaseous tracers of Arctic haze, Geophysical Research Letters, 10, 2, 144-147, 10.1029/GL010i002p00144 Abstract Springtime concentrations of hydrocarbons and chlorocarbons in the arctic atmosphere (70�N, Barrow) are reported. Concentrations of the following gases were determined: acetylene (C2H2), ethene (C2H4), ethane (C2H6), propane (C3H8), benzene (C6H6), toluene (C7H8), perchloroethylene (C2Cl4), and trichloroethylene (C2HCl3). Vertical distributions of these gases were also determined on flights during May 1982. The results show that C2Cl4, C2H2, and C2H6 may be gaseous tracers of arctic haze. Their vertical profiles suggest that polluted air may be transported to the arctic 1?2 km above ground, and perhaps also in layers higher than this level.
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Sharma, S., E. Andrews, L. A. Barrie, J. A. Ogren and D. Lavoue, (2006), Variations and sources of the equivalent black carbon in the high Arctic revealed by long-term observations at Alert and Barrow: 1989-2003, Journal of Geophysical Research-Atmospheres, 111, D14, , doi:10.1029/2005JD006581 Abstract [ 1] Fifteen years of ``equivalent'' black carbon (EBC) measurements ( derived from aethalometer measurements of light absorption) made at Alert in Nunavut, Canada, and Point Barrow in Alaska, United States, were compared for the long-term trends and seasonal cycle. Over the 15-year period from 1989 to 2003, the results revealed a downward trend in EBC concentrations by as much as 54% at Alert and 27% at Barrow for the all-year data, by 49% at Alert and 33% at Barrow for the winter data, and by 53% at Alert for the summer. It was difficult to quantify if there was a decline during the summer for Barrow since there was no clear trend. The difference in trends might be related to changes in circulation in the Arctic, variable source contribution, and/or scavenging of particles. The results revealed that EBC concentrations were 40% higher during the positive phase of the North Atlantic Oscillation than during the negative phase. The source contributions at the two sites were determined by using trajectory analysis techniques, which revealed that Alert came under the influence of Siberia/Europe transport while Barrow showed influence from Siberian and Pacific/Asian transport.
Sharma, S., M. Ishizawa, D. Chan, D. Lavoué, E. Andrews, K. Eleftheriadis and S. Maksyutov, (2013), 16-year simulation of Arctic black carbon: transport, source contribution, and sensitivity analysis on deposition, Journal of Geophysical Research: Atmospheres, , n/a-n/a, 10.1029/2012JD017774 Abstract Arctic regional climate is influenced by the radiative impact of aerosol black carbon (BC) both in the atmosphere and deposited on the snow and ice covered surfaces. The NIES (National Institute for Environmental Studies) global atmospheric transport model was used, with BC emissions from mid-latitude fossil fuel and biomass burning source regions, to simulate BC concentrations with 16 year period. The model-simulated BC agreed well with the BC observations, including the trends and seasonality, at three Arctic sites: Alert (Nunavut, Canada), Barrow (Alaska, USA), and Zepplin, Ny-Ålesund (Svalbard, Norway). The equivalent black carbon (EBC, absorption inferred BC) observations at the three Arctic locations showed an overall decline of 40% from 1990 to 2009; with most change occurring during early 1990s. Model simulations confirmed declining influence on near surface BC contribution by 70% , and atmospheric BC burden by one half from the Former Soviet Union (FSU) BC source region over 16 years. In contrast, the BC contribution from the East Asia (EA) region has little influence at the surface but atmospheric Arctic BC burden increased by 3 folds. Modelled dry deposition is dominant in the Arctic during wintertime, while wet deposition prevails at all latitudes during summer. Sensitivity analyses on the dry and wet deposition schemes indicate that parameterizations need to be refined to improve on the model performance. There are limitations in the model due to simplified parameterizations and remaining model uncertainties, which requires further exploration of source region contributions, especially from growing EA source region to Arctic BC levels in the future is warranted.
Sharma, Sangeeta, Misa Ishizawa, Douglas Chan, David Lavoue, E. Andrews, Kostas Eleftheriadis and Shamil Maksyutov, (2012), 16-year simulation of Arctic black carbon: Transport, source contribution, and sensitivity analysis on deposition, Journal of Geophysical Research, , , 10.1029/2012JD017774 Abstract Arctic regional climate is influenced by the radiative impact of aerosol black carbon (BC) both in the atmosphere and deposited on the snow and ice covered surfaces. The NIES (National Institute for Environmental Studies) global atmospheric transport model was used, with BC emissions from mid-latitude fossil fuel and biomass burning source regions, to simulate BC concentrations with 16 year period. The model-simulated BC agreed well with the BC observations, including the trends and seasonality, at three Arctic sites: Alert (Nunavut, Canada), Barrow (Alaska, USA), and Zeppelin, Ny-Ålesund (Svalbard, Norway). The equivalent black carbon (EBC, absorption inferred BC) observations at the three Arctic locations showed an overall decline of 40% from 1990 to 2009; with most change occurring during early 1990s. Model simulations confirmed declining influence on near surface BC contribution by 70% , and atmospheric BC burden by one half from the Former Soviet Union (FSU) BC source region over 16 years. In contrast, the BC contribution from the East Asia (EA) region has little influence at the surface but atmospheric Arctic BC burden increased by 3 folds. Modelled dry deposition is dominant in the Arctic during wintertime, while wet deposition prevails at all latitudes during summer. Sensitivity analyses on the dry and wet deposition schemes indicate that parameterizations need to be refined to improve on the model performance. There are limitations in the model due to simplified parameterizations and remaining model uncertainties, which requires further exploration of source region contributions, especially from growing EA source region to Arctic BC levels in the future is warranted.
Shaw, P.M, L.M Russell, A. Jefferson and P.K Quinn, (2010), Arctic organic aerosol measurements show particles from mixed combustion in spring haze and from frost flowers in winter, Geophysical Research Letters, 37, L10803, , 10.1029/2010GL042831 Abstract Submicron atmospheric aerosol particles were collected between 1 March 2008 and 1 March 2009 at Barrow, Alaska, to characterize the organic mass (OM) in the Arctic aerosol. Organic functional group concentrations and trace metals were measured with FTIR on submicron particles collected on Teflon filters. The OM varied from 0.07 ?g m?3 in summer to 0.43 ?g m?3 in winter, and 0.35 ?g m?3 in spring, showing a transition in OM composition between spring and winter. Most of the OM in spring could be attributed to anthropogenic sources, consisting primarily of alkane and carboxylic acid functional groups and correlated to elemental tracers of industrial pollution, biomass burning, and shipping emissions. PMF analysis associated OM with two factors, a Mixed Combustion factor (MCF) and an Ocean-derived factor (ODF). Back trajectory analysis revealed that the highest fractions of the MCF were associated with air masses that had originated from northeastern Asia and the shipping lanes south of the Bering Straits. The ODF consisted of organic hydroxyl groups and correlated with organic and inorganic seawater components. The ODF accounted for more than 55% of OM in winter when the sampled air masses originated along the coastal and lake regions of the Northwest Territories of Canada. Frost flowers with organic-salt coatings that arise by brine rejection during sea ice formation may account for this large source of carbohydrate-like OM during the ice-covered winter season. While the anthropogenic sources contributed more than 0.3 ?g m?3 of the springtime haze OM, ocean-derived particles provided comparable OM sources in winter.
Sheridan, P. J., R. C. Schnell, W.H. Zoller, J.J. Zieman and R.A. Rasmussen, (1993), Composition of Br-containing aerosols and gases related to boundary layer ozone destruction in the arctic, Atmospheric Environment Part A General Topics, 27, 17-18, 2839-2849, doi:10.1016/0960-1686(93)90315-P Abstract During the third Arctic Gas and Aerosol Sampling Program (March 1989), aircraft measurements of atmospheric gases and aerosols were performed in the European Arctic for the purpose of investigating the phenomenon of boundary layer O3 destruction. Eight high-volume aerosol filter samples were collected in tropospheric air over the pack ice. In these sampling periods, continuous O3 measurements were made and trace gases were collected in flasks. For all samples, total elemental bromine collected on the filters in excess of the estimated sea salt component (XSFBr) was found to anticorrelate stronly (r = ?0.90) with the mean ozone concentration observed during the sampling period. These findings are similar to earlier observations at Alert and Barrow. Air samples collected during these periods were analysed for Br-containing gases and hydrocarbons. None of these compounds were well correlated with either O3 or XSFBr concentration over the course of the experiment. This is probably because variable conditions of local meteorology, atmospheric structure and geographic location influenced the degree to which O3 was depleted, by affecting the size of the reaction reservoir and the source(s) of the reactants. Samples collected in the surface (not, vert, similar 50 m deep) isothermal or slightly stable layer (SSL) over pack ice and with light winds from the direction of the central Arctic showed the highest O3 depletions. When winds were from the direction of open water, significantly higher O3 and lower XSFBr values were observed. When the SSL was not present, samples collected below the strong inversion showed less O3 destruction and lower XSFBr concentrations than similar low altitude samples collected within the SSL. This is consistent with the notion of a larger reservoir volume available for reaction. Gas and aerosol chemistry results were compared for two samples collected close spatially and temporally over ice north of Spitsbergen. Our data indicate that (1) CHBr3 may be the key organobromine species supplying Br atoms and BrO radicals in a heterogeneous photochemical reaction cycle causing the photolytic destruction of O3 in the springtime Arctic surface layers, and (2) ambient hydrocarbons (especially C2H2) are depleted during O3 destruction, and may be important in the overall reaction mechanism. This catalytic O3 depletion process was observed to occur to an extent causing near-total O3 destruction in the SSL over a 1�2 d period. Thus, relatively rapid photochemical reactions between atmospheric Br, hydrocarbons and aerosols are suggested as driving the photolytic O3 destruction process.
Skov, H., S. B. Brooks, M. E. Goodsite, S. E. Lindberg, T. P. Meyers, M. S. Landis, M. R. B. Larsen, B. Jensen, G. McConville and J. Christensen, (2006), Fluxes of reactive gaseous mercury measured with a newly developed method using relaxed eddy accumulation, Atmospheric Environment, 40, 28, 5452-5463, doi:10.1016/j.atmosenv.2006.04.061 Abstract There is a qualitative understanding that gaseous elemental mercury (GEM) is oxidized during Arctic spring to reactive gaseous mercury (RGM) that afterwards is removed by fast deposition to snow surfaces. The conditional sampling or relaxed eddy accumulation (REA), technique represents the first opportunity to directly measure fluxes of reactive gaseous mercury (RGM) to the snow pack in the Arctic. Using a micrometeorological method REA system, with a heated sampling system specifically designed for Arctic use, the dry deposition of RGM is measured after polar sunrise, in Barrow, Alaska. Heated KCl-coated manual RGM annular denuders were used as the accumulators with an inlet allowing only fine particles to pass (Cut off diameter 2.5 mu m). At 3 in above the snow pack significant RGM fluxes were measured each spring in 2001-2004. Both depositions and emissions were observed. The emissions were attributed to chemical formation of RGM at or near the snow surface. The surface resistance, R-c, for RGM was found to be very small and set to zero as a first estimate. (c) 2006 Elsevier Ltd. All rights reserved.
Stohl, A., E. Andrews, J. F. Burkhart, C. Forster, A. Herber, S. W. Hoch, D. Kowal, C. Lunder, T. Mefford, J. A. Ogren, S. Sharma, N. Spichtinger, K. Stebel, R. S. Stone, J. Strom, K. Torseth, C. Wehrli and K. E. Yttri, (2006), Pan-Arctic enhancements of light absorbing aerosol concentrations due to North American boreal forest fires during summer 2004, Journal of Geophysical Research-Atmospheres, 111, D22, , doi:10.1029/2006JD007216 Abstract During summer of 2004, about 2.7 million hectare of boreal forest burned in Alaska, the largest annual area burned on record, and another 3.1 million hectare burned in Canada. This study explores the impact of emissions from these fires on light absorbing aerosol concentration levels, aerosol optical depths (AOD), and albedo at the Arctic stations Barrow (Alaska), Alert (Canada), Summit (Greenland), and Zeppelin/Ny Alesund on Spitsbergen (Norway). The Lagrangian particle dispersion model FLEXPART was run backward from these sites to identify periods that were influenced by forest fire pollution plumes. It is shown that the fires led to enhanced values of particle light absorption coefficients (sigma(ap)) at all of these sites. Barrow, about 1000 km away from the fires, was affected by several fire pollution plumes, one leading to spectacularly high 3-hour mean sigma(ap) values of up to 32 Mm(-1), more than the highest values measured in Arctic Haze. AOD measurements for a wavelength of 500 nm saturated but were estimated at above 4-5 units, unprecedented in the station records. Fire plumes were transported through the atmospheric column over Summit continuously for 2 months, during which all measured AOD values were enhanced, with maxima up to 0.4-0.5 units. Equivalent black carbon concentrations at the surface at Summit were up to 600 ng m(-3) during two major episodes, and Alert saw at least one event with enhanced sigma(ap) values. FLEXPART results show that Zeppelin was located in a relatively unaffected part of the Arctic. Nevertheless, there was a 4-day period with daily mean sigma(ap) > 0.3 Mm(-1), the strongest episode of the summer half year, and enhanced AOD values. Elevated concentrations of the highly source-specific compound levoglucosan positively confirmed that biomass burning was the source of the aerosols at Zeppelin. In summary, this paper shows that boreal forest fires can lead to elevated concentrations of light absorbing aerosols throughout the entire Arctic. Enhanced AOD values suggest a substantial impact of these plumes on radiation transmission in the Arctic atmosphere. During the passage of the largest fire plume, a pronounced drop of the albedo of the snow was observed at Summit. We suggest that this is due to the deposition of light absorbing particles on the snow, with further potentially important consequences for the Arctic radiation budget.
Stone, R.S., (2002), MONITORING AEROSOL OPTICAL DEPTH AT BARROW, ALASKA AND SOUTH POLE; HISTORICAL OVERVIEW, RECENT RESULTS, AND FUTURE GOALS, Abstract Atmospheric aerosols affect the Earth's radiation budget through interactions with solar and terrestrial radiation. Various committees involved with assessing global climate change recognize that aerosols can significantly impact the earth’s radiation balance. In particular, the Scientific Committee on Antarctic Research has recommended the establishment of an international network of solar spectrophotometers to monitor aerosol optical depth (AOD) at high latitudes. Although such a network now exists, better coordination is needed in order to provide research quality data to the scientific community. The U.S. National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostics Laboratory (CMDL) is collaborating with other institutes to assimilate AOD data from all polar observatories into a central archive for analysis. Historically, in situ aerosol data have been collected at CMDL baseline observatories located near Barrow, Alaska (BRW) and at South Pole, Antarctica (SPO), and since January 2000 continuous photometric measurements (during sunlit periods) have been made at these sites. An overview of past and current CMDL efforts to monitor AOD is given and some recent results are presented. Significant differences between the magnitudes and spectral signatures of AOD measured at BRW and SPO highlight the importance of assimilating similar data sets from other locations to better characterize polar aerosols spatially and temporally. Initial efforts should focus on defining natural cycles of AOD at a number of high latitude sites. Once these cycles are understood, more accurate assessments of climate forcing due to anthropogenic aerosol perturbations are possible. Through international cooperation this work can be expedited.
Stone, R. S., (1997), Variations in western Arctic temperatures in response to cloud radiative and synoptic-scale influences, Journal of Geophysical Research-Atmospheres, 102, D18, 21769-21776, JD01840 Abstract The analysis focuses on Barrow, Alaska, a site that is sensitive to changing conditions because it is located near cryospheric boundaries and is influenced by both extratropical and Arctic synoptic activity. Surface and upper air meteorological data for a 31-year period (1965�1995) are used to evaluate temperature variations as they relate to dynamical and radiative processes. Both annual and monthly analyses indicate a tendency toward warming overall. However, the annual warming is not monotonic over time and varies seasonally. Comparisons of temperature time series from four sites along the Siberian-Alaskan coastline show that Barrow is a representative site to evaluate climate change in the western Arctic coastal zone. Regionally, the warming is dominated by significant temperature increases during winter and spring, but cooling is indicated for autumn. These results are not entirely consistent with model predictions of a more uniform high-latitude warming during the cold season in response to increasing concentrations of greenhouse gases in the atmosphere. Rather, the observed changes are attributed to well-known natural processes that affect regional cloud distributions in response to changing circulation patterns. Coincident daily and hourly meteorological and radiation data are also used to demonstrate empirically how clouds modulate Arctic temperatures.
Stone, R. S., E. G. Dutton, J. M. Harris and D. Longenecker, (2002), Earlier spring snowmelt in northern Alaska as an indicator of climate change, Journal of Geophysical Research-Atmospheres, 107, d10, 10-1, doi:10.1029/2000JD000286 Abstract [1] Predictions of global circulation models (GCMs) that account for increasing concentrations of greenhouse gases and aerosols in the atmosphere show that warming in the Arctic will be amplified in response to the melting of sea ice and snow cover. There is now conclusive evidence that much of the Arctic has warmed in recent decades. Northern Alaska is one region where significant warming has occurred, especially during winter and spring. We investigate how the changing climate of northern Alaska has influenced the annual cycle of snow cover there and in turn, how changes in snow cover perturb the region's surface radiation budget and temperature regime. The focus is on Barrow, Alaska, for which comprehensive data sets exist. A review of earlier studies that documented a trend toward an earlier disappearance of snow in spring is given. Detection and monitoring activities at Barrow are described, and records of snow disappearance from other sites in the Alaskan Arctic are compared. Correlated variations and trends in the date of final snowmelt (melt date) are found by examining several independent time series. Since the mid-1960s the melt date in northern Alaska has advanced by ~;8 days. The advance appears to be a consequence of decreased snowfall in winter, followed by warmer spring conditions. These changes in snowfall and temperature are attributed to variations in regional circulation patterns. In recent decades, there has been a higher frequency of northerly airflow during winter that tends to diminish snowfall over northern Alaska. During spring, however, intrusions of warm moist air from the North Pacific have become more common, and these tend to accelerate the ablation of snow on the North Slope of Alaska. One result of an earlier melt date is an increase in the net surface radiation budget. At Barrow, net radiative forcing can exceed 150 W m-2 on a daily basis immediately following the last day of snowmelt, and as a result of an 8-day advance in this event, we estimate an increase of ~2 W m-2 on an annual basis. Our results are in general agreement with earlier analyses suggesting that reductions in snow cover over a large portion of the Arctic on an annual basis have contributed to a warming of the Northern Hemisphere (NH). In addition, the terrestrial ecosystems of the region are very sensitive to snow cover variations. There is growing concern that these perturbations are anthropogenically forced and adapting to these environmental changes will have significant social and economic consequences. While observed decreases in NH snow cover are in broad agreement with GCM simulations, our analyses suggest that internal (or natural) shifts in circulation patterns underlie the observed variations. Continued monitoring and further study is needed to determine whether the earlier disappearance of snow cover in spring in northern Alaska is an indicator of greenhouse-forced global warming or is a manifestation of a more natural, long-term cycle of climate change.
Stone, R. S., G. P. Anderson, E. Andrews, E. G. Dutton, E. P. Shettle and A. Berk, (2007), Incursions and radiative impact of Asian dust in northern Alaska, Geophysical Research Letters, 34, L14815, , 10.1029/2007GL029878 Abstract The Arctic region is sensitive to incursions of aerosols that affect its radiation balance, directly through interactions with solar and terrestrial radiation and indirectly as cloud condensation nuclei. During spring 2002 dust was transported from the Gobi desert passing over instrumented field sites near Barrow, Alaska, providing the opportunity to measure the dust properties. Empirical determinations of the direct radiative forcing by dust were used to corroborate simulations made using the Moderate Resolution Transmittance radiative transfer code, MODTRAN�5. During sunlit periods, dust cools the surface while warming those layers in which it resides, increasing atmospheric stability. At night, dust layers tend to cool while the surface warms slightly due to infrared emissions from the dust layer.
Stone, R. S., G. P. Anderson, E. P. Shettle, E. Andrews, K. Loukachine, E. G. Dutton, C. Schaaf and M. O. Roman III, (2008), Radiative impact of boreal smoke in the Arctic: Observed and modeled, JGR-Atmospheres, 113, D14S16, , 10.1029/2007JD009657 Abstract The Arctic climate is modulated, in part, by the presence of aerosols that affect the horizontal and vertical distribution of radiant energy passing through the atmosphere. Aerosols affect the surface-atmosphere radiation balance directly through interactions with solar and terrestrial radiation and indirectly through interactions with cloud particles. During summer 2004 forest fires destroyed vast areas of boreal forest in Alaska and western Canada, releasing smoke into the atmosphere. Smoke aerosol passing over instrumented field sites near Barrow, Alaska, was monitored to determine its physical and optical properties and its impact on the surface radiation budget. Empirical determinations of the direct aerosol radiative forcing (DARF) by the smoke were used to corroborate simulations made using the Moderate Resolution Transmittance radiative transfer model, MODTRAN�5. DARF is defined as the change in net shortwave irradiance per unit of aerosol optical depth (AOD). DARF, varying with solar angle and surface type, was evaluated at the surface, at the top of the atmosphere (TOA), and within the intervening layers of the atmosphere. The TOA results are compared with fluxes derived from coincident satellite retrievals made using the Clouds and the Earth's Radiant Energy System (CERES) radiance data. Smoke tends to reduce the net shortwave irradiance at the surface while increasing it within layers in which it resides. Over the Arctic tundra during summer, a layer of smoke having AOD = 0.5 at 500 nm produces a diurnally averaged DARF of about ?40 W m?2 at the surface and ?20 W m?2 at TOA, while the layer itself tends to warm at a rate of ?1 K d?1. The tendency of smoke to cool the surface while heating the layer above may lead to increased atmospheric stability and suppress cloud formation. Radiative forcing at the top of the atmosphere is especially sensitive to small changes in surface albedo, evidenced in both the model results and satellite retrievals. TOA net shortwave flux decreases when smoke is present over dark surfaces and tends to increase if the underlying surface is bright. For example, at solar noon during midsummer at Barrow, a layer of smoke having AOD(500) = 0.5 will reduce the net shortwave flux at TOA by ?30 W m?2 over the ocean while at the same time increasing it by 20 W m?2 over an adjacent area of melting sea ice. For smoke aerosol, the sensitivity of DARF to changing surface albedo (assuming a solar zenith angle of 50�) is about +15 W m?2 AOD?1 for every increase in surface albedo of 0.10. Throughout the Arctic summer, surface and TOA cooling and a tendency toward warming in the intervening atmospheric layers are the dominant radiative impacts of boreal smoke over the ocean and tundra areas, but the radiative forcing at TOA is positive over regions covered by ice or snow. Enhanced differential cooling/heating of ocean, ice, and snow due to the presence of smoke in the atmosphere may affect regional circulation patterns by perturbing diabatic processes. Should the frequency and intensity of boreal fires increase in the future because of global warming, the more persistent presence of smoke in the atmosphere may be manifest as a negative feedback at the surface. In addition, there will likely be indirect radiative impacts of the smoke as it influences cloudiness, which in turn further modulates the Arctic radiation budget.
Sturges, W.T., J.F. Hooper, L.A. Barrie and R. C. Schnell, (1993), Stable lead isotope ratios in Alaskan arctic aerosols, Atmospheric Environment Part A General Topics, 27, 17-18, 2865-2837, doi:10.1016/0960-1686(93)90317-R Abstract Aerosol samples collected at Barrow, Alaska, during February and March 1990 were found to have uniform stable lead isotope compositions. The mean 208Pb/207Pb ratio was 2.423�0.009 and the mean 206Pb/207Pb ratio was 1.161�0.014. The latter ratio is essentially the same as that obtained from an earlier study of aerosols at two Canadian stations in the High Arctic and is typical of, but not unique to, Eurasian sources of atmospheric lead. Further discriminating power was available in this study through the inclusion of 208Pb/207Pb ratios, which provided additional evidence that the former Soviet Union and eastern Europe are major contributors to atmospheric particulate lead in the Alaskan Arctic, accounting for around two-thirds of the particulate lead measured at Barrow. The remaining third of the lead is attributed to west European sources. There was no evidence for a substantial North American component, other than local contamination.
Sturges, W.T., R. C. Schnell, S. Landsberger, S. J. Oltmans, J. M. Harris and S.-M. Li, (1993), Chemical and meteorological influences on surface ozone destruction at Barrow, Alaska, during Spring 1989, Atmospheric Environment Part A General Topics, 27, 17-18, 2851-2863, doi:10.1016/0960-1686(93)90316-Q Abstract Surface ozone, particulate bromine and inorganic and organic gaseous bromine species were measured at Barrow, AK, during March and April 1989 to examine the causes of surface ozone destruction during the arctic spring. Satellite images of the Alaskan Arctic taken during the same period were also studied in conjunction with calculated air mass trajectories to Barrow to investigate the possible origins of the ozone-depleted air. It was found that during major ozone depletion events (O3<25 ppbv) concentrations of particulate bromine and the organic brominated gases bromoform and dibromochloromethane were elevated. Air mass trajectories indicated that the air had crossed areas of the Arctic Ocean where leads had been observed by satellite. The transport time from the leads was typically a day or less, suggesting a fast loss mechanism for ozone. A similarly fast production of particulate bromine was shown by irradiating ambient nighttime air in a chamber with actinic radiation that approximated daylight conditions. Such rapid reactions are not in keeping with gas-phase photolysis of bromoform, but further studies showed evidence for a substantial fraction of organic bromine in the particulate phase; thus heterogeneous reactions may be important in ozone destruction.
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Tans, P. P., K. W. Thoning, W. P. Elliot and T. J. Conway, (1990), Error estimates to background atmospheric CO2 patterns from weekly flask samples, Journal of Geophysical Research-Atmospheres, 95, D9, 14063-14070, Abstract The precision and accuracy of trends and seasonal cycles of CO2, as determined from grab samples, was investigated. First, the statistical aspects of infrequent (weekly) sampling were studied by simulating, via a partially random procedure, parallel time series of CO2 flask samples. These simulated flask series were compared to the continuous analyzer records from which they had been derived. The second approach to studying the uncertainties of flask records was to compare real flask results with simultaneous hourly mean concentrations of the in situ analyzers at the Geophysical Monitoring for Climatic Change observatories at Point Barrow, Mauna Loa, Samoa, and the south pole. The latter comparisons emphasized experimental, rather than statistical, errors. The uncertainties and sampling biases depend on the site and on the period of averaging. For monthly means the uncertainty varies from 0.2 to 0.6 ppm (one standard deviation, parts per million by volume), being largest for Barrow. Sampling biases for monthly means at Barrow and Mauna Loa are significant, up to 0.5 ppm. Experimental errors are the dominant error source for annual averages, and spurious interannual variations can be up to 0.4 ppm.
Tans, P. P., K. W. Thoning, W.P. Elliott and T. J. Conway, (1989), Background Atmospheric CO2 patterns from weekly flask samples at Barrow, Alaska: Optimal signal recovery and error estimates, in The Statistical Treatment of CO2 Data Records, NOAA Technical Memorandum, 173, 131, 112-123, Abstract Atmospheric CO2 flask sampling time series were simulated by choosing one or more hourly CO2 concentration values per week from the continuous analyzer record of the GMCC observatory at Point Barrow, Alaska using a partially random procedure. These simulated time series were analyzed using various curve-fitting techniques. After data selection, monthly averages were calculated for each simulated flask data set. These averages were compared with the parent data set from which the simulated flasks were derived. The statistical uncertainty of a monthly flask average was estimated to be between 0.4 and 0.6 ppm with optimal curve-fitting technique. Systematic biases of up to 1.3 ppm were present depending on the month and on the curve-fitting technique that was used. Increasing the sampling from once per week to twice per week did not significantly reduce the biases. The seasonal cycle was characterized by a fit with four harmonics. The harmonic coefficients were determined very tightly by only three years of flask data.
Tomasi, C, A Lupi, M Mazzola, R. S. Stone, E. G. Dutton, A. Herber, V Radionov, B Holblen, M Sorokin, S Sakerin, S Terpugova, P Sobolewski, C Lanconelli, B Petkov, M Busetto and V Vitale, (2012), An update on polar aerosol optical properties using POLAR-AOD and other measurements performed during the International Polar Year, Atmospheric Environment, 52, 29–47, 10.1016/j.atmosenv.2012.02.055 Abstract An updated set of time series of derived aerosoloptical depth (AOD) and Ångström’s exponent α from a number of Arctic and Antarctic stations was analyzed to determine the long-term variations of these two parameters. The Arctic measurements were performed at Ny-Ålesund (1991–2010), Barrow (1977–2010) and some Siberian sites (1981–1991). The data were integrated with Level 2.0 AERONET sun-photometer measurements recorded at Hornsund, Svalbard, and Barrow for recent years, and at Tiksi for the summer 2010. The Antarctic data-set comprises sun-photometer measurementsperformed at Mirny (1982–2009), Neumayer (1991–2004), and Terra Nova Bay (1987–2005), and at South Pole (1977–2010). Analyses of daily mean AOD were made in the Arctic by (i) adjusting values to eliminate volcanic effects due to the El Chichón, Pinatubo, Kasatochi and Sarychev eruptions, and (ii) selecting the summer background aerosol data from those affected by forest fire smoke. Nearly null values of the long-term variation of summer background AOD were obtained at Ny-Ålesund (1991–2010) and at Barrow (1977–2010). No evidence of important variations in AOD was found when comparing the monthly mean values of AOD measured at Tiksi in summer 2010 with those derived from multi-filter actinometer measurementsperformed in the late 1980s at some Siberian sites. The long-term variations of seasonal mean AOD for Arctic Haze (AH) conditions and AH episode seasonal frequency were also evaluated, finding that these parameters underwent large fluctuations over the 35-year period at Ny-Ålesund and Barrow, without presenting well-defined long-term variations. A characterization of chemical composition, complex refractive index and single scattering albedo of ground-level aerosol polydispersions in summer and winter–spring is also presented, based on results mainly found in the literature. The long-term variation in Antarctic AOD was estimated to be stable, within ±0.10% per year, at the three coastal sites, and nearly null at South Pole, where a weak increase was only recently observed, associated with an appreciable decrease in α, plausibly due to the formation of thin stratospheric layers of ageing volcanic particles. The main characteristics of chemical composition, complex refractive index and single scattering albedo of Antarctic aerosols are also presented for coastal particles sampled at Neumayer and Terra Nova Bay, and continental particles at South Pole.
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Xi, B., X. Dong, K. Crosby, C. N. Long, R. S. Stone and M. D. Shupe, (2010), A 10-yr Climatology of Arctic Cloud Fraction and Radiative Forcing at Barrow, Alaska, Geophysical Research Abstracts, 12, , Abstract A 10-yr record of Arctic cloud fraction and radiative forcing has been generated using data collected at the Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) site and the nearby NOAA Barrow Observatory (BRW) from June 1998 to May 2008. The cloud fractions (CF) derived from ARM radar-lidar and ceilometer measurements increase significantly from March to May (0.57!0.84), remain relatively high (0.80-0.9) from May to October, and then decrease from November to the following March (0.8!0.57), having an annual average of 0.76. These CFs are comparable to those derived from ground-based radar-lidar observations during the SHEBA experiment and from satellite observations over theWestern Arctic regions. The monthly means of estimated clearsky and measured all-sky SW-down and LW-down fluxes at the two facilities are almost identical with the annual mean differences less than 1.6 Wm
Xiquan, D., B. Xi, K. Crosby, C. N. Long, R. S. Stone and M. D. Shupe, (2010), A 10 year climatology of Arctic cloud fraction and radiative forcing at Barrow, Alaska, Journal of Geophysical Research, 115, D17212, 1-14, doi:10.1029/2009JD013489 Abstract A 10 year record of Arctic cloud fraction and radiative forcing has been generated using data collected at the Atmospheric Radiation Measurement (ARM) North Slope of Alaska site and the nearby NOAA Barrow Observatory (BRW) from June 1998 to May 2008. The cloud fractions (CFs) derived from ARM radar?lidar and ceilometer measurements increase significantly from March to May (0.57?0.84), remain relatively high (?0.80�0.9) from May to October, and then decrease from November to the following March (0.8?0.57), having an annual average of 0.76. These CFs are comparable to those derived from ground?based radar?lidar observations during the Surface Heat Budget of the Arctic Ocean experiment and from satellite observations over the western Arctic regions. The monthly means of estimated clear?sky and measured all?sky shortwave (SW)?down and longwave (LW)?down fluxes at the two facilities are almost identical with the annual mean differences less than 1.6 Wm?2. Values of LW cloud radiative forcing (CRF) are minimum (6 Wm?2) in March, then increase monotonically to reach maximum (63 Wm?2) in August, then decrease continuously to the following March. The cycle of SW CRF mirrors its LW counterpart with the greatest negative impact occurring during the snow?free months of July and August. On annual average, the negative SW CRFs and positive LW CRFs nearly cancel, resulting in annual average NET CRF of about 3.5 Wm?2 on the basis of the combined ARM and BRW analysis. Compared with other studies, we find that LW CRF does not change over the Arctic regions significantly, but NET CRFs change from negative to positive from Alaska to the Beaufort Sea, indicating that Barrow is at a critical latitude for neutral NET CRF. The sensitivity study has shown that LW CRFs increase with increasing cloud fraction, liquid water path, and radiating temperature with high positive correlations (0.8�0.9). Negative correlations are found for SW CRFs, but a strong positive correlation between SW CRF and surface albedo exists.
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Yurganov, L. N., D. A. Jaffe, E. Pullman and P. C. Novelli, (1998), Total column and surface densities of atmospheric carbon monoxide in Alaska, 1995, Journal of Geophysical Research-Atmospheres, 103, D15, 19337-19345, JD02299 Abstract The results of correlated investigations of atmospheric carbon monoxide in Alaska during the spring-summer of 1995 using three different techniques are presented. CO total column abundance was measured in Fairbanks using IR spectroscopy with the Sun as a light source. A new computer retrieval code was developed and compared with the previously used technique. Surface mixing ratios were determined in situ by gas filter correlation and by gas chromatography with a mercuric oxide reduction detector. Surface measurements were made at two uncontaminated sites: Poker Flat Research Range in interior Alaska and the National Oceanic and Atmospheric Administration Point Barrow Observatory. In spring, the measurements revealed considerably more CO in the surface layer as compared with the tropospheric mean values determined by spectroscopy. This suggests an accumulation of anthropogenic CO in the boundary atmospheric layer over vast areas of the northern hemisphere during the winter. Beginning in mid-April, the CO concentration in the troposphere decreases, but the rate of decrease in the surface layer was 2�2.5 times greater than that for the troposphere as a whole. By June the surface mixing ratios and mean tropospheric values nearly converged, and the CO mixing ratio seemed to be almost constant with altitude. The July measurements revealed days with enhanced CO total column burden; these are most likely associated with lifted layers of air, polluted by forest fires.

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