Spring and summer drought characteristics in central and eastern Inner Mongolia nearly 50 years

Based on the comprehensive meteorological drought index(CI),using data of daily temperature and precipitation of 75 weather stations which have more than 200mm precipitation a year,CI sequences and spatial and temporal distribution in spring and summer during 1961-2010 were built.It shows that:(1) Drought in spring and summer of central and eastern Inner Mongolia can be divided into three types: drought or not drought all over the central and eastern Inner Mongolia,anticorrelation of east and west part of drought,anticorrelation of north and south part of drought.(2) Drought in spring was reduce after 1980,but regional heavy drought in spring was increase;drought frequency in summer in Inner Mongolia increased.(3) Climate warming began in 1980s.Since then the precipitation distribution changed,which aggravated the summer drought.