Variations in the Diurnal Range of Surface Temperature over the Western United States

Surface temperature records stored in the MesoWest database from 1997-2006 are examined at thousands of locations in the western United States. The goal of this study is to assess the characteristics of the diurnal temperature range as a function of local physiographic features (location relative to water bodies, elevation, slope, etc.). The temperature values within a 7-day window during all available years are aggregated for each hour of each day. Rejecting extreme values through several quality control steps, climatological estimates of the mean and standard deviation for each hour of each day are obtained. In addition to computing the harmonics of the diurnal cycle as a function of season, subseasonal variations in the amplitude and variability of the diurnal temperature range are examined.

Abrupt changes in the amplitude of the diurnal range are evident in many locations as a result of elevation, intervening terrain, changes in vegetation, etc. Applications of this climatological information as part of a real-time quality control of MesoWest temperature observations are demonstrated.