Abstract:

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 intensity 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 Brahmaputra 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 insensitive to it