Elevation-dependent reductions in wind speed over and around the Tibetan Plateau

Abstract

The Tibetan Plateau (TP) affects its surroundings significantly through thermal and dynamic processes. Reductions in near-surface wind speed (Ws) have been observed from ground measurements but how the trends of Ws vary with the elevation is less clear. Trends of Ws with respect to elevation were investigated using long-term daily records taken from 1970 to 2012 of Ws and maximum (Tmax), minimum (Tmin), and mean (Tmean) air temperatures from 139 stations over and around the TP. The major findings are as follows. (1) Pronounced reductions in Ws can be observed in all seasons and annually across the TP. Spring demonstrates the most prominent weakening. The rate of reductions in Ws was amplified with elevation, and higher-elevation environments experienced greater changes in Ws than lower-elevation areas. Elevation-dependent reductions in Ws have intensified from 1970 to 2012. (2) Statistically significant negative correlations between Ws and corresponding near-surface temperatures were detected. We suggested that the elevation-dependent warming and thereby the increased surface roughness at higher-elevation environments may contribute to the elevation-dependent reductions in Ws over and around the TP. More detailed mechanisms causing this pattern are to be further explored.