The Research on Drought Characteristics of SPI at Different Time Scales in Hunan Province

Based on the monthly precipitation data of 97 national meteorological observatories in Hunan Province from 1961 to 2016, the SPI drought index of monthly, seasonal and annual scales was constructed by mathematical statistics method, and then the characteristics of drought at different time scales in Hunan Province were analyzed using SPI index. The results show that the average annual, seasonal and monthly scales drought occurrence stations in Hunan Province are 30.7, 30.5 and 30.7 respectively, and the difference between them is very small. The SPI drought index of Hunan Province is obvious interdecadal variations and evident dry-wet-dry-wet variations at the all scales. In general, Hunan Province can be divided into the uniform droughtflood pattern and the reverse drought-flood pattern in the whole province at the different time scales, and the variance of the first two modes is over 60%, which can represent the main spatial distribution characteristics of drought at different time scales. By comparing and analyzing the typical dry and wet years in different time scales, it can be found that 2002 is the same wet year in Hunan Province, 1997 is the year of north drought and south flood, 1969 and 1998 is the year of north flood and south drought.The results can provide a basis for drought prevention and mitigation in Hunan Province.