Analysis of Spatiotemporal Evolution of Isolated Rainstorm Events in Huai River Basin, China

Because of the impacts of extreme climate, the severity, areal extent, and frequency of rainstorm events are rapidly increasing, especially in the Huai River Basin of China. This article is based on hourly precipitation data of 229 meteorological stations from 1951 through 2012, combined with statistical and meteorological theory. We used the Mann-Kendall mutation test, moving t-test, and inverse distance weighting spatial interpolation to analyze the spatiotemporal evolution of precipitation, duration, intensity, and frequency of isolated rainstorm events under climate change. The main results are as follows: (1) isolated rainstorm events were obviously bimodal and their occurrence moved backward in time. Their average duration and time of maximum intensities changed dramatically, without a significant increasing trend. The period since the 2000s has seen an increase of rainstorms and their temporal regression across the entire basin. (2) The intensity of isolated rainstorm events in the study area decreased, but precipitation, its duration, areal extent, and frequency had increasing trends basin-wide. (3) Four rainstorm event indices were examined for the period of 1990–2000. Relative to the years before 2003, the average precipitation increased by 2.1%, the average total duration by 8.1%, and the average frequency of occurrence by 25.5%. All indices show smaller minimum and larger maximum values. Overall, the isolated rainstorm events tended to increase