Spatial Distribution and Evolution of Climatic Aridity in Desert Steppe in Inner Mongolia in Recent 50 Years

According to the average daily temperature and daily precipitation data from 11 meteorological stations in desert steppe in Inner Mongolia during the period of 1961—2010,the temporal and spatial variation of climatic aridity in the steppe in recent 50 years was analyzed using the improved formula of Selianinov AI and ArcGIS software.The results are as follows: ① The average aridity and aridity degree increased gradually from the southeast to the northwest;② Under the temperature increase and precipitation decrease in the steppe,the aridity index was in an increase trend in most regions except in the central-western region,that is the climatic drying trend in desert steppe in Inner Mongolia was significant;③ According to the analyzed results of aridity,the 1970s was a relatively wet decade,and the aridity increased significantly in the early 21st century.The drought area was enlarged year by year,it was enlarged for nearly three times up to the early 21st century,and the drought trend was significant;④ The 4.0-contour of aridity was gradually shifted towards the typical steppe southeastward.The 1960s was regarded as a starting decade,a relatively low variation occurred before the 1990s,but a significant variation occurred from the early 21st century.Moreover,the variation and the spatial shift amplitude were high in the east of the study area,and they were relatively low in the west.