Abstract:

According to the "Regulations for Monitoring and Evaluation of Regional Important Processes (Rainstorm)" issued by China Meteorological Administration, the localization recognition threshold of regional rainstorm processes in Yunnan province was determined, which is proved to be objective and effective by disaster data. Furthermore, the temporal and spatial distribution characteristics of regional rainstorm processes in Yunnan province from 1961 to 2022 were analysed by using the methods of climate trend analysis, Manner-Kendall test, wavelet, EOF and REOF. The results show that the comprehensive intensity of the regional rainstorm processes in Yunnan province fluctuates greatly, and ist annual mean value shows an insignificant decreasing trend, and the monthly mean value fluctuates and the peak appears in January, and the ten-day mean value in rainy season changes little. The regional rainstorm processes in Yunnan province occur four times a year on average, which shows a decreasing trend after 1977, but it is not significant, and there is no obvious abrupt change point from 1961 to 2022. The frequency of regional rainstorm processes in Yunnan province shows an unstable period of 6~8 years from 2008 to 2022. The regional rainstorm processes in Yunnan province are most frequent in summer and the least frequent in winter, accounting for nearly 70% of the annual rainstorm from mid-June to late August. The regional rainstorm processes in Yunnan province are more in the south and less in the north, although the frequency is less in the northern margin, the process precipitation intensity is larger. The regional rainstorm processes in Yunnan province are characterized by five major climatic patterns, such as most of the same pattern, southwest and northeast reverse pattern and north and south reverse pattern etc., and it can be further divided into five typical regions, namely, southern region, western region, central and eastern region, northern region and northwestern region. Over the past 62 years, the southern region, western region and central and eastern region fluctuate greatly, and the trend of change was not obvious. The northern region is stable and change little. The northwest region has mainly decreased in the early period and increased significantly in the later period.

Key words: Regional rainstorm process, EOF (Empirical Orthogonal Function), REOF (Rotated Empirical Orthogonal Functions)