Simulations for a Houston ozone episode and the NYC DHS MSG tracer study with an urbanized version of MM5

A highly urbanized version of MM5 (by use of the Martilli-Dupont-Taha scheme) has improved its performance in the simulation of Houston and NYC urban meteorology characteristics. In particular, the EPA version of MM5 (called uMM5 at SJSU) better simulates canopy-layer and PBL meteorological fields by use of a drag-force approach in lieu of typical roughness length theory. It also accepts available fine-resolution input parameters obtained from a high resolution urban LU/LC data set collected by airborne lidar. The model was used with data from both the Texas2000 field study and NYC DHS MSG UDS tracer study. Results from uMM5 and the standard MM5 models showed both more accurate urban heat islands (UHIs) and urban winds from the uMM5 simulations. In particular, the Houston low-speed results showed a strong daytime UHI, which produced a convergence of ozone into the city, while the high-speed NYC results showed no UHI and a building barrier effect that produced divergence flow around the city. The uMM5 met fields from the Houston results are being fed into the CAMX air quality model, while those from the NYC results will be used to provide time and space varying boundary conditions to a variety of rapid and CFD ER urban canopy/canyon flow and dispersion models.