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

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.