Modeling Urban Impacts on Regional Weather of Central U.S

Urbanization can notably impact regional weather. As a result, sensitivity experiments of urbanization on regional weather events were conducted for three metropolitan areas along the Ohio River: Evansville, Indiana; Louisville, Kentucky; and Cincinnati, Ohio. Using the Weather Research and Forecasting (WRFv3.2.1) model, four summer precipitation events were simulated and analyzed. The objective was to determine how the urban environment impacted these specific events. The four cases, 11 June 2006; 17 June 2006; 23 June 2006; and 29 August 2008 were selected for generally similar synoptic environments with minimal frontal influence.

The United States Geological Survey National Land Cover Dataset (USGS NLCD) of 1993 was used to determine the impacts of urbanization. Four nested domains with increasing spatial resolution were used to model these precipitation events. The two inner domains covered the three urban areas at 1-km spatial resolution. Each event was run with and without the urban canopy model (UCM). Subsequently, the influence on the urban climate was evaluated, focusing on how precipitation totals, heat flux, and planetary boundary layer heights changed.

The UCM runs had the largest improvement in model precision for daytime sensible heat flux. For small rain totals, the UCM also performed better than the control. In general, both the control and UCM overestimated precipitation totals and range.