Evaluating landsurface temprature variation and its responses to climate change and human activities ------A case study of the Yarlung Zangbo River, southeastern Tibetan Plateau

The Yarlung Zangbo River Basin (YZRB), located in the Qinghai-Tibetan Plateau, has been dramatically affected by global warming. In recent decades, serving as the indicator of coupled vegetation growth and climate variation, the spatiotemporal land surface temperature has been changed substantially by changes in environmental factors while greening spreading. In this study, we evaluated the components of water and energy cycle during 1980-2015 based on the VIC model, one of the widely recognized and applicated distributed hydrological model. The fluctuation of LST was examined and the influence of environmental elements on LST was identified. The results showed that VIC model performed a high adaptability in applying and conducting in YZRB with R over 0.7 and Er at 5.03%. Climate factors were increasing while human activities stayed stable in YZRB by our modeling. In addition, climate factors (precipitation, evapotranspiration, temperature) and underlying factors (soil moisture, NDVI, Albedo) were detected as influencing factors of LST. In YZRB, the greening was witnessed while LST showed an increasing trend. By distinguishing the climate and human activities on LST, ET and NDVI are two dominant factors effecting LST. From 1980 to 1995, LST was mainly affected by climate and its contribution rate was 70.36%. After 1995, LST was affected by human activities, and its contribution rate was 55%. Grassland with medium cover showed the potential of a cooling influence. Among all the environmental factors, Albedo showed a negative and a lagged behind effect on LST. Temp, P and ET were positively related to LST and displayed changes that are relatively in phase. SM, NDVI, were detected as leading the changes in LST, positively. Our study contributes to clarifying the mechanisms influencing LST in high-altitude and high-latitude regions under the global greening and is fundamental for socio-economic development in alpine mountainous regions.