Abstract: The characteristics of different timescale drought variations from 1961 to 2012 in Southwest China were studied, by using a new drought index (standardized precipitation evapotranspiration index, SPEI) as the division standard of droughts. The level was calculated based on the monthly precipitation and average air temperature data from 86 meteorological stations. The results show that the drought frequency at 12-month timescale presents a significant declining trend in the Yunnan-Guizhou border zone, but an inconsistent and unclear trend in other regions. The drought frequency at 6-month timescale shows a significant increasing trend in the dry period (November -April in the following year) in the whole research area, but a slowly decreasing trend in the rainy period (May-October) in most regions, particularly in southern Sichuan. The drought frequency at 3-month timescale does not indicate a significant trend in spring, but shows a significant increasing trend in autumn and winter, especially in 2000-2012.

Key words: Southwest China, standardized precipitation evapotranspiration index (SPEI), multiple timescale, drought frequency