Trends in Extreme Temperatures in Relation to Urbanization in the Twin Cities Metropolitan Area, Minnesota

Abstract

The long-term trends in extreme summer season temperatures across the Twin Cities Metropolitan Area (TCMA) associated with urbanization are examined. To assess trends in extreme temperature data, maximum and minimum temperatures from 1975 to 2002 were assembled for seven stations located in both rural and urban areas. Furthermore, urbanization since 1975 was assessed by estimating the percentage of impervious surfaces from Landsat images acquired for various years. The results of this study indicated a greater rate of increase in overall minimum temperatures, resulting in a slightly declining trend in diurnal temperature range for all of the stations. In the case of extreme temperatures, most of the peripheral urban and rural stations experienced negative trends in extreme maximum temperatures, accompanied by positive trends in extreme minimum temperatures. This was also validated by the simultaneous increase in the percentage of impervious surfaces in those locations. The greatest changes were observed for Stillwater, which is located relatively close to the heart of the TCMA but has undergone a faster rate of urbanization.