Analyzing the Effects of Urbanization on Regional Climate in the Chicago Metropolitan Area

Decades of urban development and industrial expansion have prompted climatologists to investigate the relationship between regional climate and land use change. Surface characteristics such as albedo, heat capacity, and soil moisture strongly influence the magnitude of energy fluxes within the planetary boundary layer (PBL) and are theorized to play a significant role in altering temperature and precipitation climatologies in several highly-populated U.S. cities. The urban heat island (UHI) effect, identified as a sharp nocturnal temperature gradient between the cooler rural and warmer urban regions, is one such example. Regional extremes in climate have come to the attention of the public sector and have prompted studies suggesting that the widespread conversion of grassland to urban land may lead to longer-duration, higher-frequency events. This research examines the land-atmosphere relationship during the July 1995 heat wave in the city of Chicago (an extreme temperature event known for producing abnormally high nighttime temperatures and abnormally high dew point values). The Weather Research and Forecasting (WRF) model is used to simulate the state of the atmosphere over a period of 8 days (July 10 – July 17). Comparisons are then made between simulations run over Chicago’s urban region untouched and simulations run over Chicago’s urban region converted to grassland.