Observational evidence from two mountainous regions that near‐surface wind speeds are declining more rapidly at higher elevations than lower elevations: 1960–2006

Abstract

Coupling recent observed declines of terrestrial mid‐latitude near‐surface wind speed ( u ) with knowledge that high‐elevation sites rapidly experience climate change led to an assessment of the regional near‐surface elevation dependence of u ( u Z ) at two mountainous regions (central China and Switzerland). The monthly u Z were calculated from 1960–2006. In both regions u Z were higher in winter (∼2.25 m s −1 km −1 ) compared to summer (∼1.25 m s −1 km −1 ). For the first time u Z trends were calculated, the results were strongly seasonal, ranging from ∼−0.025 m s −1 km −1 a −1 in winter to ∼−0.005 m s −1 km −1 a −1 in summer. For both regions u Z trend results showed that u has declined more rapidly at higher than lower elevations, even though different u dynamics were observed. The u Z trends have important implications for climatic changes of coupled land‐surface/boundary‐layer processes (such as evapotranspiration) at high‐elevation regions where much of the globe's fresh water is derived.