关键词: 特大干旱, 综合气象干旱指数, 特旱影响范围, 变化倾向率

Abstract:

Based on the observational data of daily temperature, precipitation and relative humidity from 97 national meteorological stations from 1965 to 2014, the daily composite meteorological drought indexes (CI) were calculated, then by using linear trend estimation, the temporal and spatial characteristics of extreme drought were analysed. The results show that the influence scope of extreme drought in the whole province expanded and the inter-annual changes presented a significant upward trend. The inter-annual change tendency of extreme droughts has been on the rise, with an average value of 0.016 times per year, the fastest rising region was in Hengshao area, and the fastest falling area was in the northeastern part of Hunan. In the whole province the extreme drought in the second half year was more than that in the first half year, and the frequency of extreme droughts in October was the highest. The analysis of the inter-decadal variation of the longest drought days at five representative stations (Sangzhi, Ningxiang, Huaihua, Zhangzhou and Shaodong) showed that the longer the duration of drought, the greater the probability of extreme drought was.The extreme drought occurred in the year when the longest drought lasted for more than 20 days, and the continuous drought  for many years was obviously more than that in a single year. The longest drought days at each representative station, occurred frequently in summer and less in spring. Cross-season drought generally spanned two seasons with the highest frequency in summer and autumn, for individual years, it spanned three seasons.

Key words: extreme drought, CI, range affected by extreme drought, the rate of extreme drought change