Seasonal Variations in Diurnal Temperature Range From Satellites and Surface Observations

Abstract

The diurnal temperature range (DTR) is an important climate-change variable and, until recently, it was derived from station observations of surface air temperature (Ta). Station-based observations are sparse and unevenly distributed, making the use of satellites an attractive option for evaluating DTR. In this study, satellite-based estimates of DTR are evaluated against ground measurements of surface skin temperature (Ts) and compared with weather-station observations based on Ta. Geographical and seasonal differences were identified in both ground- and satellite-derived DTRs. Estimates of DTR from station-observed air temperature represent all-sky conditions while satellite estimates of DTR from surface skin temperature represent clear conditions only. For both station observations and satellite estimates, DTRs at rural locations tend to be larger than at urban sites. The DTRs based on Ts are larger than those derived from Ta under both all and clear-sky conditions. Clouds tend to reduce the magnitude of the DTR. The station-observed DTRs are found to be larger in summer than in winter over the entire U.S. The satellite-derived DTRs are larger in spring and fall than in winter and summer over the eastern U.S., while they are larger in spring and summer than in fall and winter over the western part. Evapotranspiration from land vegetation and the effects of water-vapor radiative forcing have a major effect on the detected spatial and seasonal variations in the DTR patterns