Photochemical Modeling For Regulatory Applications Jim Boylan – GA EPD Praveen Amar – NESCAUM CMAS Users Forum Meeting October 14, 2010

Model Efficiency Photochemical modeling is the basis for evaluating the impacts of potential regulatory control scenarios. Increasing run time efficiency of the models will allow more alternative control scenarios to be evaluated and will lead to more informed decision making and more effective rule making.

Improved Efficiency More efficient processor scaling such that CMAQ would continue to gain efficiency as the number of processors increase. –Implement OpenMP on top of MPI –Move from netCDF3 to netCDF4 Save disk space (built-in data compression algorithm) Improve efficiency (better IO performance and indexing). Variable Time Step Algorithm

Model Accuracy Photochemical modeling for regulatory applications needs to be as accurate as possible to ensure the implemented control measures/strategies will achieve the desired results (i.e., attainment of NAAQS for ozone and PM2.5). Regulators need to have a high degree of confidence in their modeling results, especially when they are the basis for rules that require industry to spend large amounts of resources on controls.

Performance and Uncertainty Diagnostic model performance evaluations –Improve Organic Carbon PM2.5 –Improve hourly predictions of gaseous precursors (SO 2, NO x, NH 3, CO, VOCs) and speciated PM2.5 Hourly and daily NAAQS –Re-examine SO2 heterogeneous aqueous phase reaction Use of hourly observed cloud parameters and precipitation –Direct use in CMAQ or assimilated in WRF –Potential “SO 2 plus NO y ” secondary NAAQS Ability to quantify the uncertainty in model predictions and assign confidence interval

August 26 (10:00 am)

PSD Permit Applications Photochemical models should be developed for use in PSD permitting applications to evaluate criteria pollutants including SO 2, NO 2, Pb, ozone, and secondary PM 2.5 from project sources. –Long-range transport and Short-term –NACAA Secondary Formation Workgroup –Plant Washington in Georgia

Flexi-Nest/Plume-in-Grid Flexi-nest grid option that will allow the user to run coarse grid meteorology (e.g., 12-km) at finer grid resolution (e.g., 4-km or 1-km ) Plume-in-Grid is necessary to minimize the artifacts created by the instantaneous dilution of the plume in the grid. Both options are important when looking at the impact of a single source on a specific set of receptors or monitors.