内蒙古近53年连续无雨期的时空变化特征

Spatiotemporal Variations of Dry Spell in Inner Mongolia in Recent 53 Years

利用我国内蒙古自治区1960—2012年46个气象站点的逐日降水数据,分析了该地区连续无雨期的时空变化特征。计算了3个连续无雨期指数:连续无雨期次数(NDS)、连续无雨期平均日数(MDS)和最长连续无雨期日数(MLDS),并通过线性倾向估计法和MK趋势检验法研究连续无雨期指数的变化特征。结果表明:MDS,MLDS呈现自西向东的梯度递减,而NDS则呈现相反的空间分布。连续无雨期指数的空间分布表明内蒙古西部的干旱强度要高于其他区域。年尺度下,内蒙古大部分站点的NDS,MLDS呈现不显著的减少趋势,而多数站点的MDS呈现不显著的增加趋势。月尺度下,内蒙古7月、8月连续无雨期的变化特征较显著。研究区7月、8月的NDS呈显著减少趋势,而MDS,MLDS表现为显著增加趋势。连续无雨期的季节变化表明内蒙古夏季干旱化程度正逐步加重。

Base on the daily precipitation data from 46 meteorological stations in Inner Mongolia Autonomous Region, north China, the space and time changing characteristics of dry spell were investigated during the period from 1960 to 2012 in this study. The three dry spell indices such as number of dry spell （NDS）, mean length of dry spell （MDS）, and maximum length of dry spell （MLDS） were calculated, and the linear trend estimation method and MK trend test method were used to analyze the changing characteristics of dry spell indices. The results indicated that the decline of mean MDS and MLDS along the east to west gradient for has been found. Mean NDS shows an opposite distribution compared with mean MDS and MLDS. It seems to indicate that drought in the western area is much severer than other area. On the annual scale, most stations display insignificant decrease trends for NDS and MLDS, most stations display insignificant increase trends for MLDS. On the monthly scale, the changes of dry spell in July and August in Inner Mongolia are obvious. In July and August, the NDS shows significant decrease trend, the MDS and MLDS show significant increase trends. This result means that the summer droughts become increasingly serious in Inner Mongolia.