Abstract: The climatic conditions in Hunan province are complex and the probability of drought occurrence is high. To reveal the probability characteristics of drought events in various climatic regions of Hunan province (central Hunan, northeast Hunan, northwest Hunan, western Hunan, and southern Hunan), based on meteorological data from 97 meteorological stations in Hunan province during 1961−2020, standardized precipitation evapotranspiration index (SPEI) and Copula function were used to extract the duration and severity of drought events, and to study the co-occurrence recurrence periods of drought duration and severity were studied in each climatic region of Hunan province. The results showed that: (1) along the direction of southern Hunan, central Hunan, northeast Hunan, northwest Hunan, and western Hunan, the number of drought events in the climatic region was from more to less, and the value range of drought events duration and severity was from small to large. (2) When fitting the optimal marginal distribution function of drought duration and severity respectively, the number of stations fitted by GEV function exceeds 60%, and the fitting effect of the optimal marginal distribution function of drought severity was better than that of drought duration. When the joint function of drought duration and the optimal marginal distribution of severity was established, the Frank Copula function was applied to more than 50% of the sites. (3) Southern Hunan was prone to shorter duration and greater severity of drought events, while western Hunan, northwest Hunan, and some areas of northeast Hunan were prone to longer duration and greater severity of drought events. Central Hunan was not only prone to drought events with long duration and high severity but also to drought events with short duration and high severity in the southern part of central Hunan. There were differences in the probability characteristics of drought events in different climatic regions in Hunan province, and measures can be taken to reduce the harm of drought.

Key words: Hunan province, SPEI, Copula function, Drought event, Drought recurrence period