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使用2009年DOY(Day of Year)145～288时段与2001～2010年夏季(DOY 161～240时段)的Terra/MODIS16 d合成的植被指数产品数据MOD13 A2和8 d合成的地表温度(Land Surface Temperature,TLS)产品数据MOD11 A2,构建TLS～IEV(Enhanced Vegetation Index,IEV)特征空间,从而得到了条件温度植被干旱指数(Temperature Vegetation Drought Index,ITVD)反映的藏北土壤湿度空间分布。对藏北高原2009年植被生长季内土壤湿度的季节性变化及2001～2010年夏季土壤湿度的年际变化特征进行分析,研究结论表明:随着植被盖度的增大,干、湿边斜率逐渐变小,植被对环境温度的变化具有缓冲效应;藏北高原土壤湿度的季节性变化明显,主要受温度、降水、植被覆盖和冻土过程等季节性变化的影响;近10年研究区内土壤湿度有轻微的旱化趋势,但不同气候区内的年际变化表现不一致;气温表现不同程度的显著升温趋势,部分站点的降水有不显著减少趋势,其它站点降水表现为年际波动,而区域统计的ITVD值年际波动与站点气温的变化大体一致。
Vegetation index data synthesized using the Terra / MODIS16 d from 145 to 288 DOY (Day of Year) and Terra / MODIS 16 from 2001 to 2010 (DOY 161 to 240) in 2009 MOD Land surface temperature (Land Surface Temperature , TLS) product data MOD11 A2, the TLS-IEV feature space was constructed, and the spatial distribution of soil moisture in northern Tibet, as reflected by the Temperature Vegetation Drought Index (ITVD), was obtained. The seasonal variation of soil moisture in the vegetation growing season in the northern Tibet Plateau in 2009 and the interannual variability of soil moisture in the summer of 2001 ~ 2010 were analyzed. The results show that with the increase of vegetation coverage, the slope of dry and wet slopes And the vegetation has a buffer effect on the change of ambient temperature. The seasonal variation of soil moisture in the northern Tibetan Plateau is obvious, which is mainly affected by seasonal changes such as temperature, precipitation, vegetation cover and frozen soil process. In the past 10 years, Soil moisture had slight drought trend, but the interannual variations in different climatic regions showed inconsistent performance. The temperature showed significant warming tendency to different extents, the precipitation in some sites did not decrease significantly, and the precipitation in other sites showed interannual fluctuations Inter-regional fluctuations in ITVD values for regional statistics are generally in line with changes in site temperature.