Recent recovery of surface wind speed in northwest China.

Previous studies have reported that much of the surface wind speed (SWS) over the mid‐latitudes of the northern hemisphere has declined. However, very few studies have investigated the relatively recent phenomenon of wind recovery. Based on 68 wind data series, this paper examines changes in wind speed in northwest China between 1969 and 2015. In 1992, following a decade of sharply decreasing at a rate of 0.036 m s⁻¹ a⁻¹ (p < .05), the SWS began to significant increase at a rate of 0.004 m s⁻¹ a⁻¹. The specific reasons for this increase are as follows: (a) The decrease in SWS during the pre‐1992 slowdown period is the result of declining wind speeds in spring and summer, whereas increases in wind speed during the post‐1992 recovery period are caused by increased wind in winter. (b) The number of days featuring strongly varying wind speeds has changed. Specifically, the number of days above 2 m s⁻¹ all show a significant decreasing trend from 1969 to 1992, whereas the number of days of 1–3 m s⁻¹ shows a significant upward trend from 1993 to 2015. (c) Stations located between 1,000 and 1,500 m.a.s.l. (meter above sea level) are more sensitive to climate change than those at other altitudes, which shows the biggest decline (increase) trend during wind speed slowdown (recovery) period. These stations could potentially act as climatic indicators to predict future wind speed changes. SWS in northwest China have been affected by changes both in large‐scale atmospheric circulation and in regional warming. Surface pressure gradient variations between high‐ and low‐latitude regions may be important contributors to wind speed changes under asymmetric warming. However, urbanization is only moderately responsible for trend changes in SWS. [ABSTRACT FROM AUTHOR]