Climatology of the Soil Surface Diurnal Temperature Range in a Warming World: Annual Cycles, Regional Patterns, and Trends in China

Abstract

The soil surface diurnal temperature range (SSDTR), reflecting the synchronicity of changes in the daily extremes of soil surface temperatures, provides an important and sensitive indicator of climate change. The climatology of SSDTR and its trends have a strong connection with the land surface energy budget, but this has received little notice up to now. Our research examines the spatial-temporal characteristics of the annual cycle of SSDTR and its connection with other climate variables in China. The results demonstrate that the annual SSDTR curve changes gradually across space, with both regional and zonal characteristics. The shape of the annual SSDTR curve varies among regions. While it shows consistently strong positive associations with solar irradiance across China, a strong negative association with relative humidity is evident only in the dry western regions and the connection with relative humidity progressively decouples as we move toward the moist eastern regions. Atmospheric circulation affects SSDTR indirectly through derived changes in the seasonal cycles of moisture and solar irradiance. This produces a zonal character of the SSDTR annual curve in the east, while in the west the positive land-atmosphere feedback under low moisture conditions is associated with a regional character. The magnitude of the annual cycle of SSDTR is large compared with temporal change, contributing to the generally stable nature of the cycle under global warming conditions.