The analysis of the spatiotemporal variations and mechanisms for the near-surface wind speed over China in the last 40 years

This study mainly presents the spatiotemporal characteristics and changes of near-surface wind speed with observations from 679 stations over China for 1979-2019. Furthermore, mechanisms of the wind speed changes are also investigated. Major results show that the larger near-surface wind speed mainly occur in northern and eastern regions, Tibetan Plateau and the coastal zones in China. The wind speed in spring is larger than the other seasons with mean value of 2.57 m s(-1). Significantly decreased near-surface wind speed trend in China is detected during 1979-2019, particularly in 1979-1996. The mean rates of decrease in 1979-2019 and 1979-1996 are - 0.06 m s(-1) (10a)(-1) and - 0.19 m s(-1) (10a)(-1), respectively. The decreased trends of the high wind speed percentiles are more significant than the low, especially in 1979-1996. The change rate of the 95th wind speed percentile in 1979-1996 even reaches to - 0.48 m s(-1) (10a)(-1) and passes the significance test at p < 0.05. However, the wind speed trend reversed after 1997. The lowest 5th wind speed percentile has the most significant reversal trend. Therefore, the decreased wind speed trend before 1997 is mainly caused by the significant reduction of strong wind, while the reversal trend after 1997 results from weak wind. The variations of the wind speed over China attributed to both the U and V wind components. The significantly declined trend of the surface wind speed is closely related to the weakened upper westerly wind field. In addition, the uneven warming between high and low latitudes may also contribute to the surface wind speed changes through thermal adaption.