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The effects of urban environments on the dynamics of a WRF-simulated supercell thunderstorm

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Tuesday, 4 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
Larissa J. Reames, University of Oklahoma, Norman, OK; and D. J. Stensrud and D. Parsons

The goal of this study is to begin to quantify the relative importance of changes in surface roughness and thermal capacity associated with urban regions to thunderstorm dynamics. An isolated supercell storm that forms to the west of the Oklahoma City urban area and then passes north the city was simulated as a control run using the Advanced Research Weather Research and Forecasting (ARW-WRF) model with a 2.5 km horizontal resolution in the larger domain, and a 500 m resolution for the smaller domain centered over the city. Thermodynamic and dynamic variables were analyzed for this simulation prior to storm formation to quantify the effects of the urban area on its environment. In order to test the sensitivity of this supercell to urban land surface characteristics, multiple simulations were performed in which Oklahoma City, as parameterized by urban fraction, vegetation type, and land use type, was either completely removed and replaced with natural vegetation or moved to many different locations within the domain. Model runs were also performed in which Oklahoma City was replaced with different cities. For each simulation, time series of vertical motion, vertical vorticity, and updraft helicity, as well as the evolution of storm-scale wind and temperature patterns throughout the lifetime of the storm were analyzed. Because wind speed and direction, as well as near-surface temperature and wind patterns, affect storm structure and intensity, perturbation pressure and simulated radar reflectivity will also be examined and results reported.