中文摘要：

内蒙古地区农业以草原畜牧业和旱作农业为主,容易受到自然灾害,特别是干旱的影响。在气候变化的背景下,研究该地区干旱时空格局特征,对当地采取适应气候变化对策具有重要意义。为了明确内蒙古地区不同时间尺度干旱特征及其对气候变化的响应,该文选取1960-2015年内蒙古地区46个气象站点逐月气象观测数据,计算不同时间尺度标准化降水蒸散指数SPEI,结合Mann-Kendall检验、经验正交函数（empirical orthogonal function,EOF）分解、旋转经验正交函数（rotated empirical orthogonal function,REOF）分解、干旱评价指标等方法,分析了内蒙古地区56 a来干旱时空格局特征,讨论了干旱特征与太平洋年代际震荡（pacific decadal oscillation,PDO）指数的关系。结果表明：从时间变化来看,内蒙古地区干旱逐渐减轻,1976年发生突变;四季均呈变湿趋势,春季显著;全区干旱强度基本为轻旱和中旱,主要为局域性干旱和全域性干旱。从空间分布来看,内蒙古地区整体上呈西部干旱缓解、东部干旱加剧的趋势;夏季整体干旱显著加重,秋季次之,春季和冬季以减轻为主。按照干旱区域敏感性强弱可将内蒙古地区分为西部区（I区）、中部区（II区）、东北部北区（III区）和东北部南区（IV区）,其中I、II区干旱逐渐减轻,III、IV区呈偏干趋势。56 a来SPEI与PDO指数存在同相位关系,PDO指数冷相位时,内蒙古地区全区偏干,反之则偏湿。研究结果可为内蒙古地区水热状况的科学评估及干旱的监测预警和防灾减灾提供理论依据。

英文摘要：

Grassland animal husbandry and rainfed farming are two pillar industries in Inner Mongolia agriculture, and they are vulnerable to natural disasters, especially drought. Analysis of spatio-temporal distribution of drought characteristics in Inner Mongolia is important for local government to tackle climate change. In order to define the spatiotemporal distribution of drought characteristics and its response to climate change in Inner Mongolia at different time scales, monthly data from 46 meteorological stations for the period 1960-2015 were selected in this study, including monthly sunshine hours, wind speed at 10 m height, mean temperature, maximum temperature, minimum temperature, precipitation, relative humidity, station pressure and so on. The standardized precipitation evapotranspiration index（SPEI） was established using precipitation and potential evapotranspiration（ET0） data at different time scales, in which ET0 was calculated by FAO Penman-Monteith equation instead of Thornthwaite formula. In order to find out the drought characteristics, Mann-Kendall test, drought indices, climate tendency rate, empirical orthogonal function（EOF） analysis and rotated empirical orthogonal function（REOF） analysis were carried out on the precipitation, ET0 and SPEI. Considering of the pacific decadal oscillation（PDO）, the correlation of SPEI with PDO index in Inner Mongolia was also discussed. The results of this research showed that from the inter-annual changes, it showed a humid trend with an abrupt change in 1976 in Inner Mongolia. On the other hand, from the seasonal perspective, it was getting wet in spring（P〈0.05） and winter, and there was a drought trend in summer and autumn. The drought coverage appeared as the features of the local and domain drought at the annual scale, and the intensity of drought were light and moderate mainly. Spatially, the western regions had a humid trend, but it was drier in the eastern part of Inner Mongolia on the contrary. Most regions were getting dry in sum