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Updates to In-Line Calculation of Photolysis Rates
Citation:
Hutzell, Bill, David-C Wong, F. Binkowski, J. Bash, AND J. Streicher. Updates to In-Line Calculation of Photolysis Rates. 2015 CMAS Workshop, Model Development Session, Chapel Hill, NC, October 05 - 07, 2015.
Impact/Purpose:
The National Exposure Research Laboratory’s Atmospheric Modeling Division (AMAD) conducts research in support of EPA’s mission to protect human health and the environment. AMAD’s research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the Nation’s air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Description:
How photolysis rates are calculated affects ozone and aerosol concentrations predicted by the CMAQ model and the model?s run-time. The standard configuration of CMAQ uses the inline option that calculates photolysis rates by solving the radiative transfer equation for the needed actinic fluxes. The solution uses meteorological conditions and predicted concentrations at the current time step to determine extinction and scattering.ﾠ In version 5.02 of CMAQ, the inline option has shortcomings in scientific and computational areas. The former includes how extinction and scattering are calculated for clouds and aerosols. The latter area deals with poor computational efficiency and a code structure that is difficult to follow. In the next version of CMAQ, 5.1, the inline option attempts to remove these and other problems. The scientific updates make extinction and scattering from clouds more consistent to meteorological inputs. They also provide runtime options to use more accurate methods for calculating optical properties of aerosols. Regarding the computational area, the source code of the inline option has been reorganized to improve legibility and has greater efficiency regarding run-time.
