A New Fully Coupled Meteorology-Chemistry-Aerosol Model and Initial Results for Houston, Texas

Coupling of the Weather Research and Forecasting (WRF) version 2 regional meteorological model with the aerosol-chemistry mechanisms developed at Pacific Northwest National Laboratory is complete, and initial demonstration runs have been performed. WRF is the latest atmospheric sciences community model and the model framework enables advances in chemistry and aerosols to be tested and compared. This new model is well suited for simulating pollutants emitted from mega-cities through its ability to simultaneously simulate the local, regional, and synoptic impacts of aerosols. The aerosol-chemistry mechanisms that have been added are the Carbon Bond Mechanism-Zaveri photochemical (CBM-Z) module, the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) module, and the Fast-J photolysis module. These components are fully coupled and allow for on-line feedbacks between the meteorology, chemistry, aerosol, and radiative portions of the model. Aerosol feedbacks currently include the direct radiative effect, while the indirect effect of aerosols on clouds is under development and will be available at a future date. Mesh refinement, via nesting, allows higher resolution grids to be centered on areas with high emissions and strong gradients in atmospheric pollutants, whereas coarser outer nests can cover surrounding areas that are necessary for developing accurate meteorological conditions within the model as well as for determining long-range transport of trace gases and particulates. Demonstration runs have been performed, centered on Houston, Texas for the period 28 August through 2 September 2000. The simulated period corresponds with the 2000 Texas Air Quality Study (TexAQS) field campaign and thus has extensive meteorological, chemical, and aerosol measurements for verifying the model results. The domain configuration consists of three grids with horizontal grid spacings of 16, 4, and 1.33 km. Emission rates of trace gases and particulates are derived from the Texas Commission on Environmental Quality and from the Environmental Protection Agency?s National Emission Trend inventory. Results will be presented showing the radiative effect of the aerosol burden produced by the primary particulates released from the Houston metropolitan area on regional temperature distributions as well as an evaluation of the predicted concentration and spatial distribution