干旱作为频发的全球性自然灾害之一，造成了严重的社会、经济和生态环境问题。以西藏主要耕作区为研究区，2001—2015年MODIS、TRMM和SRTMDEM数据为数据源，利用植被状态指数（VCI）、温度条件指数（TCI）和降水状态指数（PCI）〖WTBZ〗等模型参量，采用空间主成分分析方法构建区域干旱综合监测模型，对模型精度和可靠性进行检核验证，并以所建模型对研究区2001—2015年逐月干旱进行识别，采用地理时空分析方法对研究区干旱变化特征及趋势进行研究。结果表明，干旱综合监测指数（DCMI）能够较好地反映区域土壤相对湿度与标准化降水蒸散指数（SPEI）的变化，干旱综合监测模型具有较好的适用性；研究区全年干旱频率在空间分布上呈现出西高东低的特征，大部分地区干旱频率小于20%，约12.41%的区域干旱频率超过20%；从不同等级干旱发生频率来看，日喀则市为轻旱、中旱易发区，重旱易发区则集中于日喀则市和昌都市的中部及东部地区；区域月际干旱频率空间格局差异较大，全年干旱易发生于1、8、11月等月份，局部地区干旱易发月份存在差异；区域年内旱情变化趋势差异性较大，10月~次年9月，旱情加剧区域呈现出随月份变化由耕作区东部向西部逐渐转移的趋势。
As one of the global natural disasters which take place frequently,drought has caused problems in society,economy,and ecological environment. Based on the MODIS,TRMM and SRTM-DEM data from 2001 to 2015 as the data sources,this paper takes the main farming area of Tibet Province,China as the research area and constructed a regional drought comprehensive monitoring model by using the spatial principal component analysis method and adopting the vegetation state index (VCI),temperature condition index (TCI) and precipitation state index (PCI).The accuracy and reliability of the model is verified.The model was then used to identify the monthly drought in the study area from 2001 to 2015,and the geospatialtemporal analysis method was used to study the characteristics and trends of drought changes in the study area.The results show that the drought comprehensive monitoring index (DCMI) can better reflect the changes of regional soil relative humidity and standardized precipitation evapotranspiration index (SPEI),and the comprehensive drought monitoring model has good applicability.The spatial distribution of annual drought frequency in the west of the study area was higher than that in the east,and the drought frequency in most areas was less than 20%,and about 12.41% of the regions had a drought frequency more than 20%.From the perspective of the frequency of droughts in different grades,Shigatse City was a light drought and moderate drought area,while the severe drought areas were concentrated in the central and eastern parts of Shigatse City and Changdu City.The spatial pattern of monthly drought frequency in the study area was quite different.The drought in the whole year was prone to occur in January,August and November,and there were differences in the drought prone months in some areas.The change trend of drought in the study area was quite different during a year.From October to September,the drought intensified area showed a trend of gradually shifting from the east to the west of the cultivated area along the month.
