The characteristics of temporal and spatial distribution of climate dry-wet conditions over Inner Mongolia in recent 30 years

Based on the climate data of 115 meteorological stations covering l971-2000 in Inner Mongolia,and adopting the integrated Selianinov formula,the changes of temporal and spatial distribution of climate dry-wet conditions over Inner Mongolia and six different ecological type regions in different years and decades were studied.The results showed that the spatial distribution of wet and dry conditions had obvious zonal distribution rule,from west to east,AI(Aridity Index) turned gradually to decrease,climate gradually became humid with longitude increasing.Spatial distribution of interannual changes showed that climatic changes of Inner Mongolia approximately had two types: Firstly,alternation of wetting and drying,it was situated western desert region and northeast Daxinganling forest district.Secondly,constantly drying;boundary of subhumid and semiarid region in Inner Mongolia northeast continually extended to southeastward,which made subhumid area decrease and semiarid region increase.Temporal distribution of interannual changes showed that in 70s,annual mean AI took on fluctuating decline and climate changes tended to humidification.In 80s,climate went through the change of drying-wetting-drying,AI fluctuated acutely.In 90s,climate went through firstly wetting and then drying,increasing extent of AI was the fastest in period of 1995~2000.In Six types of ecological regions,as to AI,the most dramatic changes took place in the typical desert region,whose contribution rate was the biggest to Inner Mongolia;the smallest changes appeared in the Daxinanling forest region and meadow grassland region.Interdecadal changes of wet and dry climate conditions showed 80s was a serious drought decade in Inner Mongolia.