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Highlights
Past Highlights
May 2007
Analysis of Air Quality Forecasts. An updated model configuration was deployed at the National Weather Service in early May 2007 for experimental O3 forecast guidance over the Continental United States. Underestimation of the regional O3 during early May was diagnosed to arise from the use of incorrect mobile emissions in the modeling system. Slight underestimation of moderate level O3 concentrations were also noted after the corrections to the mobile emissions. It was hypothesized that these underestimations could be related to O3 production in plumes associated with wildfires in Georgia throughout May. Additional model simulations that include estimates of emissions associated with these wildfires (derived using remotely sensed information from the Hazard Mapping System) are currently underway. (rohit.mathur@noaa.gov, george.pouliot@noaa.gov, brian.eder@noaa.gov)
Implementation of Pleim-Xiu Land Surface Model in the Weather, Research, and Forecasting Model (WRF).An extended abstract and presentation of the Pleim-Xiu land surface model (PX LSM), the Asymmetric Convective Model version 2 (ACM2) boundary layer model, and surface layer scheme implementation in Weather, Research, and Forecasting (WRF) model Version 2.2. was the main focus in May.
The PX LSM, surface layer exchange model, and ACM2 for the PBL, which are options in the Fifth-Generation Penn State/NCAR Mesoscale Model (MM5 PX) that have been used extensively in air quality studies, were implemented in WRF Version 2.2. In WRF, the implementation of these models allows them to be used independently (e.g., ACM2 with another LSM), although they have yet to be tested in this manner. A key difference between the MM5 and WRF implementation is an update to the parameterization of snow covered surfaces that significantly improves the simulated near-surface temperature. An evaluation of the WRF PX was completed for a summer and winter month. The WRF PX is compared to the MM5 PX and another WRF configuration with a different LSM and PBL option for accuracy of near-surface temperature, moisture, and wind. The key findings of this evaluation include evidence that the WRF PX simulations has more skill at representing near surface moisture and wind variations over a large part of the United States. The simulation of diurnal fluctuations of these variables is also better represented by the WRF PX simulation. Also, the WRF PX had a lower overall error in 10-m wind speed and direction than the other WRF simulations. We did find that the 2-m temperature had more error in the WRF PX than the MM5 and the other WRF configuration. We are actively working to correct this issue and expect to have a final version implemented by the end of the summer. (robert.gilliam@noaa.gov, jonathan.pleim@noaa.gov)
SCIENTIFIC ACCOMPLISHMENTS
A Comparison of Community Multiscale Air Quality (CMAQ) Modeling System Predictions with Observations from the North East Oxidant and Particle Study.An article is being prepared for submission in a special issue of the Journal of Atmospheric Environment on Atmospheric Chemical Mechanism. The article focuses on the comparison of predictions from the Community Multiscale Air Quality modeling system with measurements from the 2001 Northeast Oxidant and Particle Study. Two versions of the Carbon Bond chemical mechanism were used in the model: the CB-IV and CB05 mechanisms. The Mean Bias and the Root Mean Square Error for methyl hydroperoxide improved from 5.1 ppbv and 5.1 ppbv, respectively, with the CB-IV mechanism to 0.1 ppbv and 0.1 ppbv with the CB05 mechanism. The Mean Bias and the Root Mean Square Error for hydrogen peroxide improved from 0.8 ppbv and 0.8 ppbv, respectively, with the CB-IV mechanism to 0.2 ppbv and 0.3 ppbv with the CB05 mechanism. However, the Mean Bias and the Root Mean Square Error for nitrous acid with both mechanisms were poor. Recent studies suggest that emissions, heterogeneous reaction, and surface photolysis may produce additional nitrous acid in the atmosphere. When these pathways were added to the model, the Mean Bias improved from -1.0 ppbv to -0.3 ppbv and the Root Mean Square Error improved from 1.1 ppbv to 0.3 ppbv for nitrous acid. The addition of these pathways also increased the diurnally averaged hydroxyl radical and ozone by 10% and 1.7 ppbv, respectively. (sarwar.golam@epa.gov)
Community Modeling and Analysis System (CMAS) 2007 Annual Conference.CMAS is planning the 6th Annual CMAS User’s Conference for October 1-3, 2007, at the Friday Center in Chapel Hill, North Carolina. While papers from all facets of air quality modeling will be presented at the conference, the focus will be a special session on advances in understanding the sensitivity of air quality models to meteorological inputs. Papers addressing this topic are invited to be expanded into full journal articles to be published in a special issue of a scientific journal. Abstracts and presentations of other topics will be published on the internet. Other sessions will include: air quality model developments, emission inventory modeling, and analyses, air quality forecasting, model evaluation and analysis, climate variability and air quality, integrated modeling systems for environmental decision support, and urban database developments and air quality applications. As of early June, 95 papers have been submitted, approximately 35 that are related to the special journal, and 119 participants had registered. The deadline for submission of abstracts was June 9, 2007. Registration for attendance will remain open through the conference, although reduced registration rates continue only through September 4, 2007. Registration details, logistics, and other details are available on the Internet at http://www.cmascenter.org 
. (william.benjey@noaa.gov )
Evaluation of the University of California Davis aerosol module coupled to the Community Multiscale Air Quality (CMAQ) model. A sectional aerosol model that dynamically simulates gas to particle conversion has recently been coupled to CMAQ; the CMAQ‑UCD model has been applied to simulate air quality in Tampa, Florida, during May 2002. The model has been evaluated against size‑segregated and chemically speciated aerosol measurements made at three Tampa‑area sites. Modeled total aerosol sulfate and ammonium concentrations and size distributions are in good agreement with measurements, but nitrate concentrations are biased low by a factor of two. Sea salt emissions are parameterized as a function of wind speed and relative humidity. Good agreement between measured and modeled sodium and chloride concentrations indicates that the model accurately predicts average emissions and advective transport of sea salt. A manuscript describing this work has been submitted to internal review. (chris.nolte@noaa.gov)
Fusing CMAQ ozone and PM2.5 output and observational data. Results were presented to the data fusion-working group on May 29 from a data fusion method that combines spatial fields (e.g., ozone, PM2.5) from CMAQ and from spatial prediction (via block kriging) of observational data. The fusion technique provides a weighted average of these two fields where the weights are a function of the uncertainty in the kriged observations surfaces. The goal of this approach is to provide a method that is intuitive and relatively easy to implement. There are still open questions on how best to quantify uncertainty in the CMAQ surface fields. This is an ongoing discussion in the working group. R code was developed to perform block kriging and cross validation for maximum 8-hour ozone, maximum 1-hour ozone, and PM2.5 data for the NY domain under study for the fusion project. (kristen.foley@noaa.gov)
Interannual variability in climatological simulations. As part of the Climate Impact on Regional Air Quality (CIRAQ) project, the interannual variability of temperature, precipitation, surface insolation, and isoprene emissions have been compared to the variability in simulated ozone concentrations for both a 5‑summer period representing current climate and a 5‑summer period representing climate circa 2050. Comparison of the patterns in the variability suggests that changes in insolation are most important in affecting changes in ozone concentrations. Future effort in this area will focus on changes in atmospheric dilution via mixing heights and wind speed, as well as changes in particulate matter (PM) concentrations. (chris.nolte@noaa.gov)
Model predictions for Summer 2005 to support dynamic evaluation studies. A manuscript is under development on the topic of dynamic evaluation, which is the evaluation of a model=s ability to simulate air quality changes in response to changes in either emissions or meteorological conditions. The NOx SIP Call reductions in May 2004 were used as a case study for this work, and model simulations were developed for summers 2002 and 2004 to see how well the model-predicted changes in ozone compare to the observed changes. Since summer, 2004 was a much cooler and wetter summer; this comparison of ozone predictions does not isolate the influence of the NOx SIP Call emission reductions. Internal reviewers for the manuscript strongly encouraged the development of a summer 2005 simulation as well, since the meteorology was much more similar to 2002. Given the importance of this study and the reviewer recommendations, summer 2005 simulations were developed and have been incorporated into the analysis. Revisions are currently underway to update the results and discussion sections of the manuscript to include the 2005 results. (alice.gilliland@noaa.gov)
Modifying Community Multiscale Air Quality (CMAQ) to allow for changes in methane concentration. Methane (CH4) plays an important role in determining tropospheric ozone concentrations. However, because it is a slow‑reacting, well‑mixed chemical species, CH4 is not dynamically simulated in regional‑scale air quality models such as CMAQ, but is instead held constant. As part of the Climate Impact on Regional Air Quality (CIRAQ) project, a sensitivity simulation was conducted with the CH4 concentration increased from the current value of 1.85 ppm to 2.40 ppm, which is the projected global concentration at 2050 under the Intergovernmental Panel on Climate Change's A1B greenhouse gas emissions scenario. This simulation was compared to the base case simulation for a future summer period, which kept methane at the current value of 1.85 ppm. The result was that the daily maximum 8‑h average ozone concentrations were increased by 0.5‑2 ppb throughout most of the U.S. This result has been incorporated into a revised manuscript, which is under journal review. (chris.nolte@noaa.gov)
Results from Community Multiscale Air Quality (CMAQ) Model Simulations to Assess the Impact on Ozone from Point Source NOx Emission Reductions. Statistical performance metrics have been computed on a set of daily maximum 8‑hour ozone concentration pairs composed of modeled values from Community Multiscale Air Quality (CMAQ) model base case simulations and CASTNet (Clean Air Status and Trends Network) site data for the 3‑month summer 2002 modeling period. Based on journal peer‑reviewer comments, the evaluation results will be incorporated into the revised version of a manuscript entitled "Modeling Assessment of Point Source NOx Emission Reductions on Ozone Air Quality in the Eastern United States.” This paper presents the modeling results on the effects of major point source emission reductions of nitrogen oxides (NOx), associated with EPA's NOx SIP (State Implementation Plan) Call program, on maximum 8‑hour ozone concentrations across a domain covering the eastern half of the United States. Model differences between the base case and post‑control scenarios revealed notable decreases in daily maximum 8‑h ozone concentrations, particularly within and downwind of the greater Ohio River Valley where numerous major point sources experienced significant NOx emission reductions of up to 90%.
A related effort involving a detailed examination of the model's process analysis (PA) results has been completed on an investigation of the changes to the various physical and chemical processes, which contribute to the hourly ozone concentrations in the modeling scenarios. A manuscript entitled "Influence of Point Source NOx Emission Reductions on Modeled Processes Governing Ozone Concentrations and Chemical / Transport Indicators," describes the differences in the spatial and temporal variations in the individual physical and chemical processes between the base case and emission reduction scenarios. Model PA results were examined from a set of case study days during summer 2002 exhibiting a synoptic pattern with southwesterly wind flows conducive to pollutant transport from the mid‑western source region toward the northeastern states. Spatial patterns of the ozone chemical production rate and the physical process (i.e. vertical mixing, horizontal and vertical advection, and dry deposition) terms displayed lower values in the emission reduction scenario results in the same areas exhibiting decreases in ozone concentrations. Of particular importance, ozone chemical production rates during the mid‑day and afternoon periods were found to be dramatically lower downwind of major point sources due to significant NOx emission reductions and consequently, ozone concentrations dropped by 15‑20 ppb from base case values. Analysis of the ozone to NOx concentration ratio, a key indicator of the atmospheric chemical state, revealed considerably higher ratio values in the NOx reduction simulation results, which indicates a marked shift toward more NOx ‑limited conditions after the emission controls. On the other hand, a notable effect of the emission reductions was to increase the ozone production efficiency (OPE), the ratio of ozone to total reactive nitrogen species produced, within the plume‑impacted areas of the eastern United States. (james.godowitch@noaa.gov)
Revised Parameterization of Heterogeneous N2O5 Reaction Probability. Model results for wintertime particulate nitrate are quite sensitive to the reaction probability of dinitrogen pentoxide (γN2O5) on wetted particle surfaces. In the Community Multiscale Air Quality (CMAQ) model version 4.6, γN2O5 was updated to include a dependence on temperature and RH based on the work by Evans and Jacob (Geophys. Res. Lett., 32: L09813, 2005). Following the release of CMAQ v4.6, we discovered that the published parameterization of γN2O5 contains a typographical error and is based on only a subset of the available laboratory measurements of γN2O5. Upon recognizing these shortcomings, Division scientists developed a new parameterization of γN2O5 by fitting all of the published laboratory data. A regression equation was developed using tests for statistical significance and a weighting function that accounts for reported uncertainty in the laboratory measurements. The form of our final equation is simpler than the one by Evans and Jacob, yet it captures the dependencies of gN2O5 on temperature and RH that have been measured in several laboratories. The revised parameterization will be incorporated into the next CMAQ model release. (davis.jerry@epa.gov, kristen.foley@noaa.gov, prakash.bhave@noaa.gov)
COMPUTER INFRASTRUCTURE SUPPORT
Programming support for the Data Fusion Studies. Developed programs to generate both observed and modeled data files needed to data fusion studies that combine observed and predicted air quality fields for air quality characterization fields. These files are needed to compare different techniques for merging or fusing modeled and observed data sets. Modifications to the cmp_airs program to compute the maximum hourly and maximum 8-hour values of the neighboring grid cells of each site. (steve.howard@noaa.gov)
Extracting Emissions Data. Used the MRGGRID routine from Sparse Matrix Operator Kernel Emissions Modeling System (SMOKE) to merge daily emissions together. The daily fire emissions were merged for the 2001ai case. (alfreida.torian@noaa.gov)
Editing CMAQ Manual. "Operational Guidance for the Community Multiscale Air Quality (CMAQ) Modeling System" version. 4.6. This document was written by Institute of the Environment, University of North Carolina, Chapel Hill, NC. (alfreida.torian@noaa.gov)
CONFERENCES, WORKSHOPS AND PRESENTATIONS
COST Action 728 Workshop. Dr. Jason Ching attended the COST (European Cooperation in the field of Science and Technological Research) Action 728 Workshop on “Urbanization of meteorological and air quality models,” held on May 3-4, 2007 at the United Kingdom Met Office. His presentation, “Conceptual database system for urban model development and applications,” provided examples and illustrations from on urban morphology and databases from the National Urban Database and Access Portal Tools (NUDAPT) project, which is being sponsored by EPA’s Advance Monitoring Initiative (AMI) program. The presentation showed how NUDAPT is seeking to build a specialized database of urban variables and parameters capable of running advanced meteorological and air quality models for the nation’s major urban areas. When completed, NUDAPT will contain high resolution building data and derived products such as urban canopy parameters, guided anthropogenic heat, and population (on a diurnal basis). A database for Houston, Texas, is being created to serve as the project’s primary prototype. (Additional prototypes in this initial demonstration will include the urban areas of Atlanta, Georgia and Phoenix, Arizona). Illustrations of the NUDAPT’s portal tool, which will enable public access to the urban database, were included in the presentation. In general, the discussion regarding the conceptual framework for actions towards advancing urbanization of models was positive and well received. (jason.ching@noaa.gov)
Earth System Modeling Framework (ESMF) Community Meeting, Boulder, Colorado, May 30 – June 1, 2007. David Wong attended this meeting.
Environmental Protection Agency’s Modeler’s Workshop. Division staff participated in EPA’s regional, state, and local air quality modeler’s workshop in Virginia Beach, Virginia on May 15-17, 2007. This workshop provided a forum for modelers from EPA’s Office of Air Quality Planning and Standards (OAQPS), EPA’s regional offices, other federal agencies and state and local air pollution agencies to discuss EPA’s current air quality dispersion models and their applications. (vlad.isakov@noaa.gov)Inverse Modeling. The previously developed method for resolving the relationship between NOx emissions and NO2 concentrations modeled by CMAQ and observed by the SCIAMACHY satellite by incorporating direct sensitivities and the Kalman Filter inverse was presented at the 16th Annual International Emissions Inventory Conference in Raleigh, NC. (sergey.napelenok@noaa.gov)
Principal findings data analysis workshop, TexAQS II / GoMACCS, Austin Texas, May 29 - June 1, 2007. The meeting was attended by Jonathan Pleim. Division scientists also contributed to the following presentation at the meeting: Dimitriades, B. and D. Luecken, “An observational investigation of Ozone sensitivity to VOC and NOx, and its variation in the HGB ozone non-attainment area,” presented at Principal findings data analysis workshop, TexAQS II / GoMACCS, Austin Texas, May 29 - June 1, 2007.
OTHER ACTIVITIES
Comparison of chemical mechanisms. Prepared a manuscript on comparison of predictions by the CB05, CB4, and SAPRC99 chemical mechanisms for ozone and gas-phase precursors. The manuscript is based on expansion of a presentation made at the International Conference on Atmospheric Chemistry held in Davis CA, November 2006. This paper is being prepared for the dedicated issue of Atmospheric Environment. (luecken.deborah@epa.gov)
VISITORS
PUBLICATIONS
Published Paper
Pour-Biazar, A., R.T. McNider, S.J. Roselle, R. Suggs, G. Jedlovec, D.W. Byun, S. Kim, C.J. Lin, T.C. Ho, S. Haines, B. Dornblaser, and R. Cameron. Correcting photolysis rates on the basis of satellite observed clouds, Journal of Geophysical. Research, 112, D10302, doi:10.1029/2006JD007422 (2007).
Yu, S., P. V. Bhave, R. L. Dennis, and R. Mathur. Seasonal and regional variations of primary and secondary organic aerosols over the continental United States: Observation-based estimates and Model evaluation, Environmental Science & Technology, Web publication date: May 26, 2007.
Reff, A., B.J. Turpin, J.H. Offenberg, C.P. Weisel, J. Zhang, M. Morandi, T. Stock, S. Colome, and A. Winer. A functional group characterization of organic PM2.5 exposure: Results from the RIOPA study, Journal of Atmospheric Environment, Vol. 41, pp 4585-4398 (2007).
Papers in Press
Sarwar, G. and P. V. Bhave. Modeling the effect of chlorine emissions on ozone levels over the eastern United States. Journal of Applied Meteorology and Climate.
Papers in Journal Review
Luecken, D.J. Technical challenges involved in implementation of VOC reactivity-based control of ozone, Environmental Science and Technology, May 3, 2007.
Otte, T.L. The impact of nudging in the meteorological model for retrospective air quality simulations. Part I: Evaluation against national observation networks. Journal of Applied Meteorology and Climatology, May 25, 2007.
Otte, T.L. The impact of nudging in the meteorological model for retrospective air quality simulations. Part II: Evaluation collocated meteorological and air quality observations. Journal of Applied Meteorology and Climatology, May 25, 2007.
Papers in NOAA Review
The Environmental Impact of Atmospheric NH3 Emissions under Present and Future Conditions in the Eastern United States, Pinder, R.W., Dennis, R.L., Gilliland, A.B., to be submitted to Geophysical Research Letters
Intercomparison of SCIAMACHY and OMI 1tropospheric NO2 columns: observing the diurnal 2evolution of chemistry and emissions from space 3, K. Folkert Boersma, Daniel J. Jacob, Henk J. Eskes, Robert W. Pinder, Jun Wang, Ronald J. van der A, to be submitted to Geophysical Research
Modeling of urban an dregional aerosols-application of the CMAQ-UCD aerosol model to a coastal urban site, Christopher G. Nolte, Parkash V. Bhave, Jeff R. Arnold, Robin L. Dennis, K. Max Zhang, and Anthony S. Wexler, to be submitted to Environment Science and Technology
Papers in ASMD Review
The following draft conference paper for International Technical Meeting paper has been submitted:
S.L. Napelenok, R.W. Pinder, A.B. Gilliland, R.V. Martin. Developing a method for resolving NOx emission inventory biases using Discrete Kalman Filter inversion, direct sensitivities, and satellite‑based NO2 columns. Proceedings of the 29th International Technical Meeting on Air Pollution Modeling and its Application. September 2007. Aveiro, Portugal.
Hutzell, B. and D. Luecken. Fate and transport of emissions for several toxic metals over the United States.