Variation Characteristics of Rainstorms in Middle-Lower Reaches of the Yangtze River in Recent 60 Years

To investigate the variation characteristics of rainstorms in the middle-lower reaches of the Yangtze River from 1958 to 2017, four rainstorm characteristic variables were defined based on daily precipitation data of 426 stations. The tendency analysis and mutation test were conducted using a linear trend analysis, cumulative anomaly test, sliding t-test, and the Pettitt test. Results showed that: 1) There was a gradual decrease of the average annual rainstorm and rainstorm days from central Jiangxi to the surrounding areas, and a gradual increase of the average annual rainstorm intensity and rainstorm variation coefficient from south to north. The four rainstorm characteristics variables showed evident seasonal differences. Most rainstorms occurred in the order: summer > spring > autumn > winter. However, the largest rainstorm variation coefficient can be found in winter, showing strong volatility in winter. 2) An increasing tendency in average annual rainstorms, rainstorm days, and rainstorm intensity was observed at 74% of all the stations. The linear trend rates of the average annual rainstorms and rainstorm days gradually increase from northwest to southeast. In addition, the ratio of stations having significant increasing (p < 0.05) in the annual rainstorms and rainstorm days were 17.8% and 16.7%, respectively. 3) Results of the cumulative anomaly test, sliding t-test, and Pettitt test indicated that a significant change of rainstorms occurred in 1988 in the middle-lower Yangtze River Valley. Meanwhile, the average and trend rates of three rainstorm characteristic variables significantly increased after 1988.