| Many efforts to simulate urban effects on convective precipitation omitted microphysical effects, while others produced convection as an undesired by-product of urban heat island (UHI) simulations. The current study thus uses Project ATLANTA data, and MM5 with quadruple nested grids to investigate a UHI initiated convection case over Atlanta, Georgia. The specific hypothesis tested is that urban-induced convergence zones initiate convective precipitation.; Results show significant precipitation from a quasi-stationary front south of Atlanta and from UHI-induced convergence around the urban edges. When Atlanta roughness lengths and thermal properties were removed, the second precipitation region was eliminated, thus showing its urban origin. Results show good correlation between the surface UHI, convergence, and vertical velocity. Urban precipitation, however, was simulated somewhat northeast of the observations, about 3 h too early, but around the correct magnitude. Future simulations will focus on correcting these differences by further refinements of input urban surface parameters. |
