50 a来内蒙古荒漠草原气候干燥度的空间分布及其演变特征

根据内蒙古荒漠草原11个气象观测站1961-2010年的日平均气温、降水量资料，采用改进的谢氏干燥度计算公式，并利用ArcGIS软件分析内蒙古荒漠草原50 a来气候干燥度的时空变化规律。结果表明：① 平均干燥度呈条带状自东南向西北逐渐递增，表明干燥程度由东南向西北逐渐加强；② 除中部偏西（海流图地区）干燥度减少、气候趋于湿润化外，其他地区干燥度指数呈增加趋势，说明内蒙古荒漠草原地区气候干旱化趋势明显；③ 20世纪70年代属于相对湿润期，21世纪初干旱程度明显加大。其结果导致干旱区面积随年代增加，至21世纪初干旱区面积增加了近3倍，从另一个侧面说明研究区域气候干旱化趋势显著；④ 干燥度4.0等值线向东南方向移动，逐渐侵入典型草原。以20世纪60年代为基点， 90年代前变幅相对较小，21世纪初的偏移范围最大。此外，该线在研究区域东部变化强烈，空间位移幅度大，西部相对变化较弱，空间位移相对较小。

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.