中文摘要：

基于MODIS数据利用垂直干旱指数模型和重心模型分析了2011年4月～2012年4月的雅鲁藏布江流域干旱动态变化，并就干旱对植被的胁迫作用做了进一步探讨。研究发现：（1）干旱强度减弱区主要分布于雅鲁藏布江流域的中部，而干旱强度增强区则主要集中于该流域的上游及下游地区；（2）2012年4月份雅鲁藏布江流域的总体干旱强度相比2011年4月有所加重，轻度干旱、重度干旱区均有所增长，而湿润区则有一定减小。干旱强度加重较大的区域主要分布于拉萨河流域及〉3000～4000m、〉4000～5000m高度带；（3）雅鲁藏布江流域的NDVI与PDI的重心迁移具有很好的负相关性，说明其干旱动态变化对植被具有较明显的胁迫作用。

英文摘要：

Based on MODIS,the study analyzes the dynamic change of drought intensity between April 2011 and April 2012 with the models of gravity center and the perpendicular drought index in the Brahmaputra river basin,then it takes a further explore of impact on the vegetation. The results show as follows. （1）The region of weakened drought intensity was mainly located in the middle reaches of the Brahmaputra River which included Shigatse City,Jiangzi County, Qushui County,Renbu county and Zhanang county, while zone of the aggravated drought intensity was mainly concentrated in the upstream and downstream of the Brahmaputra River such as Lunggar county,Zhongba county and Cuole county. （2） On the whole, the in- tensity of the drought in April 2012 had been aggravated than that in April 2011 in the Brahmaputra River Basin. Areas of mild drought, severe drought increased, however the areas of wet reduced. The regions of severely aggravated drought intensity were mainly distributed in the Lhasa River Basin and the belts of 3 000~4 000 m and ~4 000~5 000 m such as Naqu county,Linzhou county and Mozhugongka county. （3） The transfer trajectory of gravity center indicated that：NDVI and PDI had a good negative correlation,thus the vegetation was apparently under the stress of the drought. Of all the vegetation types in the Brahmapu- tra River Basin, the sub-alpline sclerophyllous coniferous forest, sparse forest of high mountain, subtropical and tropical coniferous forest of mountain were the most sensitve to the PDI,however the types of alpine sparse vegetation, corps which harvest once each year, subalpine deciduous broadleaved forest were insensi=tive to it.