Abstract: The cumulative dry days and the drought frequency are calculated using the meteorological drought composite index (CI) based on the data about daily precipitation and daily average temperature collected from 90 meteorological stations in Southwest China (Sichuan, Yunnan, Guizhou Province and Chongqing City) during the time period from 1962 to 2017.Using the wavelet analysis and linear trend, the temporal and spatial variation of cumulative dry days and frequency in the span of 56 years are analyzed in detail. In addition, the atmospheric circulation profiles of the years with lower and higher value are investigated too using correlation and composition analysis. The conclusions are summarized as follows: (1) The overall trend of cumulative dry days and frequency are gradually decreased, the decade anomaly between the two is positive correlated from 1960s to 1980s, negative correlated in 1990s and positive correlated again at the beginning of the 21^st century. (2) The duration (the accumulative dry days) has an inter-annual variation period of 5 years and 9 years, and a decade-wise variation period of 12 years. The drought frequency has an inter-annual variation period of 8 years and a decade-wise variation period of 20 years. (3) The duration and frequency have the same center area with higher values including the west Sichuan and the middle and north Yunnan, and the same center area with lower values including the west of Yunnan, the middle and east of Guizhou and Chongqing. (4) The relevant circulation analysis indicated it is to the disadvantage of precipitation in the region if without water vapor and the uplift dynamics in each of the high, middle and low layers atmospheric circulation.

Key words: meteorological drought composite index (CI), temporal and spatial distribution, atmospheric circulation