Spatiotemporal variation of upper-air and surface wind speed and its influencing factors in northwestern China during 1980–2012

Abstract

Scientists generally believe that human activities and atmospheric circulations have important effects on wind speed changes; however, the main driving factors of wind speed at different times and in different areas are far from clear. Here, based on monthly wind speed data in the northwestern China during 1980–2012, we analyzed the spatiotemporal variations in wind speed and their relationship with atmospheric circulations. The results showed that (1) annual surface wind speed (SWS) displayed a decreasing trend (− 0.032 m/s/10a) during 1980–2012; SWS increased only in winter. In contrast, annual upper-air wind speed (UWS) exhibited an increasing trend; UWS presented a declining trend only in summer. (2) Human activities were likely the major cause of decrease in SWS, whereas the enhancement of the Asian Meridional Circulation (AMC, R = 0.50, P < 0.01) was an important factor for the increase in SWS in winter. (3) Annual UWS exhibited an increasing trend (0.176 m/s/10a) in the troposphere. This trend was closely related to the weakening of the Eurasian Zonal Circulation (EZC, R = − 0.52, P < 0.01) and the enhancement of the Siberian High (SH, R = 0.48, P < 0.01) during the winter, whereas the enhancement of the Eurasian Zonal Circulation (EZC, R = − 0.60, P < 0.001) in summer was the prime reason for the decrease in UWS in summer. (4) UWS increased significantly (0.38 m/s/10a) in the lower stratosphere, and this trend was mainly associated with the weakening of the Pacific Decadal Oscillation (PDO, R = − 0.40, P < 0.05).