Distinct North–South Contrasts in Precipitation Category Changes and Associated Mechanisms over the East Asian Monsoon Region ^※

As the climate warms, understanding differential changes in precipitation characteristics becomes critical for water resource management and climate adaptation. However, regional divergence in precipitation category changes, ranging from light to very heavy categories across the East Asian monsoon region, and their physical mechanisms remain unclear. Utilizing daily observations and ERA5 reanalysis data (1961–2021), this study reveals distinct north–south contrasts in precipitation category changes, with different drivers between subregions. The results show that significant reductions in light precipitation days occur in both subregions, but only the south exhibits increased heavy and very heavy precipitation days. In the northern subregion (NSR), decreased light precipitation amount accounts for ~40% of the total precipitation reduction, with little change in other categories. Conversely, in the southern subregion (SSR), increases in heavy and very heavy precipitation amounts dominate the total precipitation increase, while light and moderate precipitation show negligible changes. Mechanistic analysis indicates that near-surface warming reduces lower-tropospheric stability and relative humidity, thereby decreasing light precipitation days in both subregions. In the NSR, this decrease in light precipitation is intensified by slight moisture loss and weakened upward motion. In the SSR, weakened East Asian summer monsoon circulation limits northward moisture transport, increasing local moisture retention. Concurrently, enhanced upward motion strengthens dynamic uplift, with these combined moisture and dynamic drivers intensifying moisture convergence to trigger increased heavy and very heavy precipitation. All these advance predictive understanding of hydroclimate extremes and support targeted climate adaptation strategies.