Spatiotemporal variations in precipitation of different magnitudes in China during 1961–2020 and their contribution analysis

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Based on daily precipitation data from 754 meteorological stations across China during 1961–2020, we investigated the spatiotemporal variations in precipitation amount, precipitation days, and precipitation intensity for four precipitation magnitudes (light, moderate, heavy, and torrential rain) in both monsoon and non-monsoon regions. A partial-derivative-based contribution decomposition method was developed to quantitatively separate the independent contributions of changes in precipitation days and precipitation intensity at different magnitudes to changes in annual total precipitation (OP). The results show that the multi-year average OP in the monsoon region (1036.6 mm) was approximately 5.5 times that in the non-monsoon region (187.8 mm). Precipitation in the monsoon region was dominated by moderate rain and above, whereas light rain dominated in the non-monsoon region. During 1961–2020, OP increased significantly in the non-monsoon region, mainly driven by significant increases in light and moderate precipitation. In contrast, the monsoon region exhibited only a weak increasing trend in OP, with significant increases in light and torrential precipitation. In the non-monsoon region, increases in precipitation days were mainly associated with light-rain days (LD) and moderate-rain days (MD), whereas changes in precipitation intensity were insignificant. In the monsoon region, LD and torrential-rain days (TD) increased significantly, while moderate-rain intensity (MI) and heavy-rain intensity (HI) decreased significantly. Contribution analysis revealed that the increase in OP in the non-monsoon region was dominated by LD (77.7%). In the monsoon region, the increase in OP was mainly dominated by TD (80.4%), with LD contributing 58.7%, whereas MI and HI showed strong negative contributions (−30.4% and −28.0%, respectively). These findings indicate that the precipitation regime in China is undergoing systematic structural changes. The monsoon region has entered a new stage in which increased torrential-rain frequency dominates changes in total precipitation, posing greater challenges for flood control. Meanwhile, the wetting trend in the non-monsoon region, driven primarily by increased LD, may benefit ecological restoration but could also increase the risk of agricultural diseases.

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