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The primary source for the relative wind data was the PMEL "Skyvane" anemometer that was located at the top of the aerosol sampling mast. For periods of missing data from the PMEL data source the ships IMET SSSG wind sensor was used. We assume that the relative wind information is primarily used to determine periods of ship contamination, thus we are using the anemometer that is closest to the sample inlet. This anemometer also was used as an input to the algorithm that turned off the sample pumps during periods of ship contamination.)
The one second relative wind speed and direction data were separated into orthogonal components of "keel" and "beam". These components were averaged into 1 minute averages, and then recombined to relative wind vectors. Wind speed is reported meters per second and wind direction is in degrees with -90 being wind approaching the ship on the port beam, 0 degrees being wind approaching the ship directly on the bow, and +90 degrees being wind approaching the ship on the starboard beam.
Wind Components/ True Wind Speed/ True Wind Direction:
True wind speed and direction were calculated from measurements
obtained with
the Ships IMET wind sensor. This sensor was mounted 15.5 meters above
the
sea
surface on the ship's meteorological sampling mast at the bow and
should be
less affected by bending of streamlines as the air moves over the ship.
(The
PMEL “Skyvane” was on the top of the Aero-Van and in the ‘perturbed
airflow’.)
The true North and East components of the wind vector from the 10
second
SCS data
were calculated and then averaged into 1 minute intervals in m/s. The
true wind
vector was calculated from these components and is given as wind speed
in m/s
and wind direction in compass degrees. The WindU and WindV are
the east and
north components of the wind vector (in m/s).
One minute averages in degrees C. There were four possible sources, the 2 PMEL rotronics sensors (T1 and T2) and the ship's SSSSG IMET sensor and SSSG Vaisala WXT5 sensor. Of the four temperature records, the T1, T2 and WXT5, agreed the best, the SSSG-IMET sensor was generally 1 to 2 degrees C cooler than the other 3. As the SSSG-WXT5 data record had less gaps it was used for this data set except for several short data gaps where the PMEL T-1 sensor was used.
There were two PMEL rotronics sensors (RH1, and RH2) and one Ship
IMET
sensor (on the IMET Bow mast). Of the three, the PMEL RH1 and the
Ship IMET sensor agreed very well (generally withing 2%) and the PMEL
RH2 sensor was gererally about 5% higher than the other two. For
this reacord the PMEL RH1 sensor was used as the primary sensor, and
when there were data gaps in the PMEL record the ship IMET sensor was
used.
The rainfall rate was measured with a Scientific Technology Inc. ORG-100 Optical Precipitation Intensity Sensor. The instrument was mounted on the railing of Aero van. The dynamic range of the sensor is 0.5 to 1600 mm/h. Spikes in the signal may be associated with sea spray and/or fog. It appears that the instrument malfuctioned after 6-April, as it reported a rainrate of zero from that point on. The data are reported in units of mm/hr.
PMEL SO2
Inlet and Instrument
Air was pulled from 18 m above sea level down the 20 cm ID powder-coated aluminum aerosol sampling mast (6 m) at approximately 1 m3min-1. At the base of the sampling mast a 2.8 Lmin-1 flow was pulled through a 0.32 cm ID, 1m long Teflon tube, a Millipore Fluoropore filter (1.0-um pore size) housed in a Teflon filter holder, a Perma Pure Inc. Nafion Drier (MD-070, stainless steel, 61 cm long) and then through 2 m of Telfon tubing to the Thermo Environmental Instruments Model 43C Trace Level Pulsed Fluorescence Analyzer. The initial 1 m of tubing, filter and drier we located in the humidity controlled (25%) chamber at the base of the mast. Dry zero air (scrubbed with a charcoal trap) was run through the outside of the Nafion Drier at 2 Lmin-1. Data were recorded in 10 second averages. The data have not been filtered for periods when Knorr ship exhaust entered the mast.
Standardization:
Zero air was introduced into the sample line upstream of the Fluoropore filter for 10 minutes every 6 hours to establish a zero baseline. An SO2 standard was generated with a permeation tube held at 40ºC. The flow over the permeation tube, diluted to 4.6 ppb, was introduced into the sample line upstream of the Fluoropore filter for 10 minutes every 24 hours. The limit of detection for 1 min averaged data, defined as 2 times the standard deviation of the signal during the zero periods, was 100 ppt. Data below detection limit are listed as 0 in the ACF file and -8888 in the ICARTT format file. Missing data are listed as -9999. Uncertainties in the concentrations based on the permeation tube weight and dilution flows are <5%.
Seawater DMS
Seawater entered the ship at the bow, 3.7 m below the ship waterline, and was pumped to the ship laboratory. Every 30 minutes a 5 ml water sample was valved from the ship water line directly into a Teflon gas stripper. The sample was purged with hydrogen at 80 ml/min for 5 min. DMS and other sulfur gases in the hydrogen purge gas were collected on a Tenax filled trap, held at -5 deg C. During the sample trapping period, 6.2 pmoles of methylethyl sulfide (MES) were valved into the hydrogen stream as an internal standard. At the end of the sampling/purge period the trap was rapidly heated to +120 deg C and the sulfur gases were desorbed from the trap, separated on a DB-1 megabore fused silica column held at 70 deg C, and quantified with a sulfur chemiluminesence detector. Between each water sample the system analyzed either a DMS standard or a system blank. The system was calibrated using gravimetrically calibrated DMS and MES permeation tubes. The precision of the analysis has been shown to be ± 2% based on replicate analysis of a single water sample at 3.6 nM DMS. The automated DMS system is described in greater detail in Bates et al. (J. Geophys. Res., 103, 16369-16383, 1998; Tellus, 52B, 258-272, 2000). The major improvements since these papers are a new automation-data system and a more reliable cold trap consisting of an electrically heated stainless steel tube embedded in an aluminum block that is cooled to -5 deg C with a thermoelectric cooling chipAerosol Mass
Spectrometer,
AMS
Concentrations of submicrometer NH4+, SO4=, NO3-,
and POM were
measured with a Quadrupole Aerosol Mass Spectrometer (Q-AMS) (Aerodyne
Research
Inc.,
Version 0 data have
been
corrected for collection efficiency based on aerosol acidity. The
aerosol
acidity correction is based on the NH4/SO4 ratio and uses the same
correction
algorithm as used in TexAQS. The
detection limits from individual species were determined by analyzing
periods
in which ambient filtered air was sampled and are calculated as three
times the
standard deviation of the reported mass concentration during those
periods. The detection limits during
ICEALOT were 0.04, 0.2, 0.06, and 0.2 ug/m3 for sulfate, ammonium,
nitrate, and
POM, respectively. Samples below these
detection limits are listed as 0 in the ACF file and -8888 in the
ICARTT format
file. Missing data are listed as -9999.
Version 1 data: The sulfate frag waves were corrected. The acidity correction algorithm was adjusted based on comparisons with the impactor SO4 data.
Jayne, J.T., D.C. Leard, X. Zhang, P. Davidovits,
K.A.
Smith, C.E. Kolb, and D.R. Worsnop, Development of an aerosol mass
spectrometer
for size and composition analysis of submicron particles, Aersol Sci.
Technol.,
33, 49-70, 2000.
Allan, J.D., J.L. Jimenez, P.I. Williams, M.R. Alfarra, K.N. Bower,
J.T. Jayne,
H. Coe, and D.R. Worsnop, Quantitative sampling using an Aerodyne
aerosol mass
spectrometer. Part 1: Techniques of data interpretation and error
analysis, J.
Geophys. Res., 108(D3), 4090, doi:10.1029/2002JD002358, 2003.
Aerosol OC/EC
Contact person: Tim Bates, tim.bates@noaa.gov
1. Inlet
Aerosol particles were sampled 18m above the sea surface through a heated mast that extended 5 m above the aerosol measurement container. The mast was capped with a cone-shaped inlet nozzle that was rotated into the relative wind to maintain nominally isokinetic flow and minimize the loss of supermicrometer particles. Air was drawn through the 5 cm diameter inlet nozzle at 1 m3 min-1 and down the 20 cm diameter mast. The lower 1.5 m of the mast were heated to dry the aerosol to a relative humidity (RH) of <25%. This allowed for constant instrumental size cuts through variations in ambient RH. Twenty three 1.9 cm diameter electrically conductive polyethylene or stainless-steel tubes extend into this heated zone to direct the air stream at flows of 30 l min-1 to the various aerosol sizing/counting instruments and impactors. The efficiency of the mast inlet is discussed in Bates et al. (JGR 2002).
2. Sample collection
Stainless-steel tubes extending from the base of the sampling mast supplied air at 30 l min-1 to each of the impactors used for organic aerosol sampling. Two-stage and one-stage multi-jet cascade impactors (Berner et al., 1979) sampling air at <25% RH were used to determine the submicrometer and sub 10 micrometer concentrations of organic carbon (OC) and elemental carbon (EC). The 50% aerodynamic cutoff diameters, D50,aero, were 1.1 and 10 mm. For the data reported here, submicrometer refers to particles with Daero < 1.1 mm at <25% RH and supermicrometer, the difference between the concentrations measured with the two impactors, refers to particles with 1.1 mm < Daero < 10 mm at <25% RH. A 47mm quartz filter (Pall Gelman Sciences, #7202, 9.62 cm2 effective sample area) was used as the stage 1 filter in these impactors. An additional quartz filter was used as the backup filter to assess sampling artifacts.
A third submicrometer impactor with two quartz filters was deployed downstream of a 30 cm long diffusion denuder that contained 18 parallel strips (34 faces) of 20.3 cm x 2.8 cm carbon-impregnated glass fiber (CIG) filters separated by ~1.8 mm. The denuder cross-sectional area was 9.6 cm2.
The quartz filters were cleaned on board ship by baking at 550˚C for 12 hours. The cleaned filters were stored in Al foil lined (press-fitted) petri dishes, sealed with Teflon tape, in a freezer dedicated solely to these filters. After sample collection the filters and substrates were returned to their petri dishes and stored in the freezer until analysis. All samples were analyzed on board ship.
3. Filter sample analysis
The analysis of the filter samples was done using a Sunset Laboratory thermal/optical analyzer. The instrument heated the sample converting evolved carbon to CO2 and then CH4 for analysis by a FID. The thermal program was the same as that used during ACE-Asia (Schauer et al.2003, Mader et al., 2003). Four temperature steps were used to achieve a final temperature of 870°C in He to drive off OC. After cooling the sample down to 550°C, a He/O2 mixture was introduced and the sample was heated in four temperature steps to 890˚C to drive off elemental carbon (EC). The instrument measured the transmission of laser light through the filter to enable the separation of EC from OC that charred during the first stages of heating.
No correction has been made for carbonate carbon in these samples so OC includes both organic carbon and carbonate carbon if it was present.
4. Uncertainties
The uncertainties associated with positive and negative artifacts in the sampling of semi-volatile organic species can be substantial [Turpin et al., 1994; Turpin et al., 2000]. An effort was made to minimize and assess positive (adsorption of gas phase species) and negative (volatilization of aerosol organic species which may have resulted from the pressure drop across the impactor and filter) artifacts by using a denuder upstream of the impactor and by comparing undenuded and denuder-filter samplers. Results from these comparisons have shown that after correcting for sampling artifacts, measured OC concentrations can vary by 10% between samplers [Mader et al., 2003]. Other sources of uncertainty in the OC mass include the air volume sampled (5%), the area of the filter (5%), 2 times the standard deviation of the blanks measured over the course of the experiment (0.44 µg/cm2) which was on average 40% of the sample, and the precision of the method (5%) based on the results of Schauer et al. [2003]. The total uncertainty, calculated as the sum of the squares was 13%. Sub-micrometer OC values were always above the detection limit of 0.1 to 0.8 ug/m3 which varied with volume. Missing values are denoted with a -9999. The supermicrometer OC values are the difference between generally similar numbers. Samples where the difference was insignificant (<0.1 ug/m3) are denoted with a -8888.
Sources of uncertainty in the EC mass include the air volume sampled (5%), the area of the filter (5%), and the precision of the method (5%) based on the results of Schauer et al. [2003]. The total uncertainty, calculated as the sum of the squares was 9%. The limit of detection varied from 0.015 to 0.12 ug/m3 based on the volume sampled. Values below the detection limit are denoted with a -8888. Missing values are denoted with a -9999. The supermicrometer EC values were not above detection limit.
5. Data reported in archive
The following OC/EC data sets are reported in the data archive:
Bates,
T.S., D.J. Coffman, D.S. Covert, and P.K. Quinn (2002). Regional marine
boundary layer aerosol size distributions in the Indian,
Eatough, D.J., B.D.
Grover, N.L. Eatough, R.A. Cary, D.F.
Smith, P.K. Hopke, and W.E. Wilson, Continuous measurement of PM2.5
semi-volatile and nonvolatile organic material. Presented at the 8th
International Conference on Carbonaceous Particles in the Atmosphere,
Mader, B.T., J.J. Schauer, J.H. Seinfeld, R.C. Flagan, J.Z.Yu, H. Yang, Ho-Jin Lim, B.J. Turpin, J. T. Deminter, G. Heidemann, M. S. Bae, P. Quinn, T. Bates, D.J. Eatough, B.J. Huebert, T. Bertram, and S. Howell (2003). Sampling methods used for the collection of particle-phase organic and elemental carbon during ACE-Asia, Atmos. Environ., in press.
Schauer, J.J., B.T. Mader, J. T. DeMinter, G. Heidemann, M. S. Bae, J.H. Seinfeld, R.C. Flagan, R.A. Cary, D. Smith, B.J. Huebert, T. Bertram, S. Howell, J. T. Kline, P. Quinn, T. Bates, B. Turpin, H. J. Lim, J. Z. Yu, H. Yang, and M. D. Keywood (2003). ACE-Asia intercomparison of a thermal-optical method for the determination of particle-phase organic and elemental carbon, Environ. Sci. Technol., 37, 993-1001, 10.1021/es020622f.
Turpin, B.J., J.J. Huntzicker, and S.V. Hering, Investigation of organic aerosol sampling artifacts in the Los Angeles Base, Atmos. Environ., 28, 23061-3071, 1994.
Turpin, B.J., P. Saxena, and E. Andrews, Measuring and simulating particulate organics in the atmosphere: problems and prospects, Atmos. Environ., 34, 2983-3013, 2000.
Aerosol Ion Chemistry Data
Contact persons: Tim Bates, tim.bates@noaa.gov; Trish Quinn, patricia.k.quinn@noaa.gov
Two-stage multi-jet cascade impactors (Berner et al., 1979) sampling air at <25% RH
were used
to determine the sub- and supermicrometer
concentrations of Cl-, Br-,
NO3-, SO4=, methanesulfonate (MSA-),
oxalate (Ox-),
Na+, NH4+, K+, Mg+2, and Ca+2. Sampling periods ranged from
The impaction stage at the inlet of the impactor was coated with silicone grease to prevent the bounce of larger particles onto the downstream stages. Tedlar films were used as the collection substrate in the impaction stage and a Millipore Fluoropore filter (1.0-um pore size) was used for the backup filter. Films were cleaned in an ultrasonic bath in 10% H2O2 for 30 min, rinsed in distilled, deionized water, and dried in an NH3- and SO2-free glove box. Filters and films were wetted with 1 mL of spectral grade methanol. An additional 5 mLs of distilled deionized water were added to the solution and the substrates were extracted by sonicating for 30 min. The extracts were analyzed by ion chromatography [Quinn et al., 1998]. All handling of the substrates was done in the glove box. Blank levels were determined by loading an impactor with substrates but not drawing any air through it.
Non-sea salt sulfate concentrations were calculated from Na+ concentrations and the ratio of sulfate to sodium in seawater. Concentrations are reported as ug/m3 at STP (25C and 1 atm). Values below the detection limit are denoted with a -8888, missing data are denoted with a -9999.
Berner et
al., Sci. Total Environ.,
13, 245 -
261, 1979.
Quinn et al., J. Geophys. Res., 105, 6785 - 6805,
2000.
Gravimetrically-determined Aerosol Mass
Contact persons: Tim Bates, tim.bates@noaa.gov; Trish Quinn, patricia.k.quinn@noaa.gov
Two-stage multi-jet cascade impactors (Berner et al., 1979) sampling air at <25% RH were used to determine sub- and supermicrometer aerosol mass concentrations. The RH of the sampled air stream was measured a few inches upstream from the impactor. The 50% aerodynamic cutoff diameters, D50,aero, were 1.1 and 10 um. Submicrometer refers to particles with Daero < 1.1 um at <25% RH and supermicrometer refers to particles with 1.1 um < Daero < 10 um at <25% RH.
The impaction stage at the inlet of the impactor was coated with silicone grease to prevent the bounce of larger particles onto the downstream stages. Millipore Fluoropore films were used as the collection substrate in the impaction stage and a Millipore Fluoropore filter (1.0-um pore size) was used for the backup filter. Films were cleaned in an ultrasonic bath in 10% H2O2 for 30 min, rinsed in distilled, deionized water, and dried in an NH3- and SO2-free glove box.
Films and filters were weighed at PMEL with a Cahn Model 29 and Mettler UMT2 microbalance, respectively. The balances are housed in a glove box kept at a humidity of <25%. The resulting mass concentrations from the gravimetric analysis include the water mass that is associated with the aerosol at <25% RH.
The glove box was continually purged with room air that had passed through a scrubber of activated charcoal, potassium carbonate, and citric acid to remove gas phase organics, acids, and ammonia. Static charging, which can result in balance instabilities, was minimized by coating the walls of the glove box with a static dissipative polymer (Tech Spray, Inc.), placing an anti-static mat on the glove box floor, using anti-static gloves while handling the substrates, and exposing the substrates to a 210Po source to dissipate any charge that had built up on the substrates. Before and after sample collection, substrates were stored double-bagged with the outer bag containing citric acid to prevent absorption of gas phase ammonia. More details of the weighing procedure can be found in Quinn and Coffman [1998].
Concentrations are reported as ug/m3 at STP (25C and 1 atm). Missing data are denoted with a -9999.
Berner et
al., Sci. Total Environ.,
13, 245 -
261, 1979.
Quinn et al., J. Geophys. Res., 105, 6785 - 6805,
2000.
Aerosol Trace Elements:
Contact persons: Tim Bates, tim.bates@noaa.gov;
Trish Quinn, patricia.k.quinn@noaa.gov
Concentrations of Al, Si, Ca, Ti, and Fe were
determined by
thin-film x-ray primary and secondary emission spectrometry [Feely et
al.,
1991; Feely et al., 1998]. Submicrometer and sub-10 um samples
were
collected on Teflo filters (1.0 um pore size) mounted in Berner
impactors
having a D50,aero of 1.1 um and 10 um jet plates, respectively (Berner
et al.,
1979). Supermicrometer elemental concentrations were determined
by
difference between the submicrometer and sub-10 um
concentrations. This
method of sample collection allows for the sharp size cut of the
impactor while
collecting a thin film of aerosol necessary for the x-ray
analysis.
Sampling periods ranged from
Berner et al., Sci. Total Environ., 13, 245
- 261,
1979.
Feely et al., Geophys. Monogr. Ser., vol. 63, AGU,
Feely et al., Deep Sea Res., 45, 2637 - 2664, 1998.
U.S.Dept of Commerce / NOAA / OAR / PMEL / Atmospheric Chemistry