Urbanization-Induced Land Use Change Enhances Tornado Potential
Tornadoes pose enormous risk of casualty and economic loss in the United States. Compared to other landscapes, urban areas are more vulnerable to the tornado hazard because of the higher concentration of population and wealth. As the most extreme case of land-use change, urbanization modifies the physical properties of the underlying surface and the boundary layers, which could potentially impact the processes related to tornado formation and development. Here we explore the impact of urbanization-induced land use change on the tornado potential based on a tornadic supercell case on 1 July 2015 in Kansas City using WRF-Chem model simulations at 1 km grid spacing. The multi-layer urban canopy model Building Environment Parameterization coupled with Building Energy Model is used for urban canopy parameterization. We find that the urban land use can significantly increase tornado potential and risk compared to the simulation with the Kansas City replaced by the surrounding cropland, mainly through enhancing the streamwise horizontal vorticity and its transport into the supercell updraft regions. The stronger streamwise horizontal vorticity and its advection come from two main sources – the stronger and faster westward propagation of storm outflow boundary and the stronger baroclinic vorticity generation near the supercell updraft core area. Both of these enhancements are associated with the faster storm development and stronger storm intensity caused by the urban land effect.