Larissa Reames-March 24th

Influence of a Great Plains urban environment on a simulated supercell

The effect of urban areas on weakly-forced precipitation systems has been studied extensively. However, interactions between urban areas and synoptically-active convection, such as supercells, remain relatively unexamined. The present study uses simultions of a supercell thunderstorm to quantify the impacts of a large Plains urban area on the evolution and strength of a supercell thunderstorm. An initial ensemble of simulations (CTRLE) of a supercell over homogeneous land use is performed using the ARW-WRF model. Additionally, 108 simulations are conducted in which the land use pattern of Dallas-Ft. Worth is placed inside the model domain, with the city center shifted to be  in or near the path of the supercell. Simulations with urban areas are compared to CTRLE, with the aid of hierarchical clustering analysis to form statistically similar groups of simulations. In this analysis, the effects of the storm having various city-relative paths, as well as the storm lifecycle stage during urban interactions, are investigated. These comparisons concentrate on differences in boundary layer characteristics prior to storm formation as well as changes in supercell structure, dynamics and evolution. In addition, a factor separation approach is undertaken to determine the relative importance of roughness and thermal characteristics of urban areas on storm modification. City locations near the beginning and end of the storm’s life cycle are used to determine if the storm’s maturity while interacting directly with the city modulates these effects.