Coupled Atmospheric Chemistry Schemes for Modeling Regional and Global Atmospheric Chemistry

William R. Stockwell
Howard University
27 July, noon in 2155

Atmospheric chemistry models are used for air quality forecasting and these require chemical reaction mechanisms to simulate the production of air pollution. Chemical boundary conditions are another necessity for the simulations. Global models may be used to provide boundary conditions to regional models. NOAA/NCEP uses the Community Multi-scale Air Quality Model (CMAQ) for air quality forecasting and one of its standard chemical mechanisms is the Regional Atmospheric Chemistry Mechanism, Version 2 (RACM2). The goal of this project is to develop the Global Atmospheric Chemistry Mechanism (GACM), a global version of RACM2. GACM is intended for use in global scale atmospheric chemistry models to provide chemical boundary conditions for regional scale simulations by models such as CMAQ. GACM includes additional chemistry for marine environments while reducing its treatment of the chemistry needed for highly polluted urban regions. This keeps GACM’s size small enough to allow it to be used efficiently in global models. GACM’s chemistry of volatile organic compounds (VOC) is highly compatible with the VOC chemistry in RACM2 allowing a global model with GACM to provide VOC boundary conditions to a regional scale model with RACM2 with reduced error. The GACM-RACM2 system of mechanisms should yield more accurate forecasts by regional air quality models such as CMAQ.