Uncovering seasonal wind speed changes across China using surface and upper-air observations

Wind speed is a critical factor influencing hydrological cycles, aviation safety, and renewable energy production. While previous studies have extensively assessed changes in wind speed across China, most have focused on wind speed at ten meters (WS10), with limited attention given to upper-air wind speed (UWS). This study reveals considerable differences in changes and variability of both WS10 and UWS across China, utilizing surface and radiosonde observations. The results indicate a widespread and consistent decline in WS10 throughout China, followed by a recovery trend in many regions since the early 2000s, aligning with findings from prior research. In contrast, UWS does not exhibit consistent seasonal trends across the seasons. During winter, most regions of China have experienced increasing UWS trends, particularly in northern areas. However, in summer, UWS trends shift significantly toward negative values, especially at higher pressure levels. Vertically, coherent trends between the lower and upper troposphere are primarily observed in winter and summer, likely influenced by the strong westerly jet stream and East Asian monsoon circulation, respectively. Instead of following the long-term trends observed in WS10, UWS displays considerable interannual variations. These findings underscore the importance of considering vertical, regional, and seasonal dimensions when assessing wind changes and variability in China.