The evolution characteristics of drought spatio-temporal law in China in the recent 30 years

Under the background of climate change, continuously understanding the evolution characteristics of the spatiotemporal law and the new changes of drought in China plays a very important role in drought prevention and mitigation response, water resources development and utilization, and ecological environmental protection. Based on the historical daily Meteorological Drought Composite Index(MCI) in China, the characteristic indices and statistical methods were used to analyze the climate characteristics, inter decadal change and overall change trends, and extreme feature of drought in China and the ten major river basins in the recent 30 years, and the main conclusions are as follows: ① There were two high centers of annual drought intensity averaged from 1991 to 2020, which one is located in Huanghuai, Jianghuai and most Jianghan regions, and the other in south part of South China, Yunnan, southeastern Sichuan, and western Guizhou. The areas with frequent drought days were basically the same as the centers with high intensity. ② Although the overall drought intensity has generally shown a gradual decrease in the recent three decades, extreme drought years occur from time to time. There are obvious inter-decadal changes in the spatial location and range of the center of high drought intensity, with the widest range occurring in the 1990s. ③ Since 1991, annual drought intensity have shown strengthening trend in the south of Southwest China, southern Jiangnan, eastern South China etc., while weakening trend in most areas of north part to the Yangtze River and western South China. Only the trend of some stations is significant. As far as the ten major river basins are concerned, the drought have weakened in northern and strengthened in southern river basins. The southwest river basin has become significantly heavier. ④ Central and eastern Yunnan, northwestern Guangxi, southwestern Guizhou, and Hainan are the high centers with the strongest continuous drought intensity and the longest continuous drought days. The years with strongest drought intensity and most drought days in most northern river basins are occurred at the end of the 20th century and the beginning of the 21st century. But in the Yangtze River, Pearl River and Southwest River basins appeared in the recent five years.