Modeling the boundary layer over Galveston Bay and the Gulf of Mexico for air pollution studies

Coastal areas have large contrasts in temperature and mixing height which affect the transport of pollutants. In the Houston/Galveston area, the large, shallow Galveston Bay intrudes into the otherwise northeast-southwest coastline. At times, a "Bay breeze" pattern distinct from the larger scale "Gulf breeze" can be distinguished. Because the most intense pollutant sources are near the Bay, this has important effects on concentrations of ozone and aerosol. Measurements of winds and boundary layer structure over the water have been scarce.

Gradients of pollutants can be very sharp, and the scales of important physical processes are also small, so rather fine resolution is required to model these phenomena. The Advanced Research core of the Weather Research and Forecasting (WRF) model system is run for six days, 28 August – 2 September 2006. Comparisons are made with mixing heights measured by Doppler lidar and surface fluxes from a flux package on the NOAA Research Vessel Ronald H. Brown in Galveston Bay and the Gulf of Mexico. Emphasis is placed on the modeling and measurements over the waters of the Bay and Gulf. The weakly convective boundary layer over the water is well captured. We find that the land surface behavior and initialization of the model are the most important items in producing realistic simulations.