50a来内蒙古荒漠草原气候干燥度的空间分布及其演变特征

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

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;③20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。

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 AreGIS soft- ware. 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 e year, it was enlarged for nearly three times up to the early 21st century, and the drought trend was nlarged year by 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 are- a, and they were relatively low in the west.