An Evaluation of Summer Discomfort in the United State Using a Relative Climatological Index

A relative climatological index is developed to evaluate interregional variations in human discomfort and the impacts of weather on a variety of socioeconomic parameters. The “weather stress index” is designed to assess the frequency and magnitude of the most uncomfortable weather conditions, and data inputs are limited to air temperature, dewpoint, and wind speed. The index is constructed by calculating the apparent temperature using a simple algorithm and comparing how a particular day's apparent temperature varies from the mean for that day at that locale. The index ranges from 0 percent to 100 percent, with the most uncomfortable apparent temperatures exhibiting the highest values. A geographical distribution of July apparent temperatures at the 95 percent and 99 percent weather-stress-index level indicates that the central and south central United States experience the highest apparent temperatures in the nation. These conditions occur when the surface flow permits maritime air to intrude while a 500-mb ridge is present to encourage atmospheric subsidence. The combination of these events almost never occurs in the Desert Southwest, and the highest apparent temperatures here do not reach the levels encountered in the central United States. The use of the weather stress index should enhance interregional evaluation and facilitate the development of large-scale models for analyses of numerous climate-impact relationships.