Analysis on the Causes of Climate Change in Surface Wind Speed in Northeast China During Winter and Spring Over the Past 40 Years

This study investigates the variability, long-term trends, and potential drivers of near-surface wind speed in Northeast China over the past four decades, utilizing daily average surface wind observations and reanalysis data. The region experienced a significant shift from decreasing to increasing wind speeds, with a clear inflection point in 2013. Empirical Orthogonal Function (EOF) decomposition identified two dominant modes of wind speed variation. The first mode exhibited a sustained decline, particularly pronounced in spring, linked to enhanced easterly winds and weakened westerly winds, reduced temperature gradients associated with global warming, and a decrease in transient eddy intensity at 850 hPa. The second mode displayed a decrease followed by an increase, with a particularly strong increase in winter wind speeds, associated with eastward-propagating Rossby wave trains triggered by the cooling of north Atlantic sea surface temperatures (SST). These wave trains formed significant low-pressure systems over Northeast China, intensifying cyclonic activity and subsequently increasing wind speeds. The spatial extent and enhancement effects in spring were smaller compared to those in winter, primarily confined to the lower atmosphere. This research elucidates the complex mechanisms underlying seasonal wind speed variations in Northeast China, providing a foundation for understanding wind energy changes in the context of climate change.