Interannual Changes in Springtime Near‐Surface Wind Speed Over Eastern China Associated With the Nonlinear Combined Effects of Large‐Scale Circulation Changes

Near‐surface wind speed (NSWS) is a key meteorological variable regulating energy, water vapor, and momentum exchanges between the land surface and the planetary boundary layer. While long‐term trends and interdecadal variability of NSWS have been extensively investigated in China, the causes of its interannual variability remain insufficiently understood. This study conducts a analysis of springtime NSWS (NSWSspr) over eastern China during 1970–2020, identifies the underlying causes of its interannual change. Results indicate that NSWSspr exhibited a statistically robust quasi‐four‐year oscillation, and it was modulated by coordinated anomalies in large‐scale atmospheric circulations over the North Pacific, Northeast Asia, and the Northwest Pacific. Specifically, the simultaneous occurrence of the cyclonic anomaly over the North Pacific and Northeast Asia and the anticyclonic anomaly over the subtropical Northwest Pacific generated a substantially enhanced meridional pressure gradient, which driven stronger anomalous westerlies over the mid‐latitudes, as evidenced by the intensified E‐vector divergence and Rossby wave activity flux under the combined events. The enhanced westerlies, in turn, amplified the synoptic‐scale eddy–mean flow interaction, which further reinforced the large‐scale circulation anomalies through a positive feedback. Importantly, the substantial and statistically robust nonlinear component played an important role in amplifying the NSWSspr response. Linear superposition failed to reproduce either the magnitude or the spatial structure of the NSWSspr anomalies.