Spatial Modes And Main Mechanisms Of Altitude-dependent Warming In The Qinghai-Tibet Plateau

Based on the Moderate-resolution Imaging Spectroradiometer Land Surface Temperature(MODIS LST)data with 0.05°×0.05° resolution and the data of 122 meteorological stations from 2001 to 2018,we study the variation of them and the characteristics of elevation dependent warming(EDW)over the Tibetan Plateau(TP).Besides,the ability of MODIS LST to investigate EDW over the TP is evaluated.Then,according to ecosystem zones of the TP,we study the spatial mode of EDW of MODIS LST.Finally,snow-albedo feedback and soil moisture-sensible heat feedback is used to explain the spatial mode of EDW.The main conclusions are as follows:(1)On the annual scale,the mean,maximum and minimum surface air temperatures have significant characteristics of EDW;while the seasonal variation is different,the mean,maximum and minimum surface air temperatures have more significant characteristics of EDW in autumn and winter than which in annual.The mean and daytime MODIS LST can well reproduce the observed characteristics of EDW on the annual and seasonal scales.On the annual scale,mean and daytime MODIS LST have significant EDW characteristics in>2km and 2-5km area,but not in>5km area;on the seasonal scale,the mean and daytime MODIS LST in summer,autumn and winter have significant EDW characteristics,but not in spring;on>5km area,there has negative EDW characteristics in summer and winter.(2)The characteristics of EDW are different in 11 ecosystem zones.Take the daytime MODIS LST as an example.On the annual scale,except for the northwestern edge IID3 and southwestern edge IIC1 of the TP,there are significant characteristics of EDW in other subregions.The EDW of IB1,IIAB1 and OA1 in the southeastern of the TP,IID1 and IID2 in the western edge of the TP are relatively strong.Therefore,the overall EDW of the TP shows a higher spatial mode in the southeastern,the western margin and the Qaidam Basin,and the rest is lower;in 2-5km IB1,IC1,IIAB1,IIC2,IID2,OA1 in the eastern part of the TP and IID1 in the western edge of the TP has a significant EDW characteristics;except for IID1 in the western edge of the TP and IB1 in the middle of the TP,there is no significant EDW characteristics when the elevation is more than 5 km.On the seasonal scale,in spring and autumn,IC1 and some subregions even have negative characteristics of EDW.(3)Snow cover has a great influence on the absorption of shortwave radiation through the snow-albedo feedback,which affects the change of temperature.On the annual scale,snow-albedo feedback has a great contribution to the overall EDW;on the seasonal scale,in summer and autumn,the snow-albedo feedback has a great contribution to the overall EDW,but this mechanism has little effect on the overall EDW in winter.In addition,the of soil moisture-sensible heat feedback also has an important impact on the annual and seasonal warming of higher elevation(>5km)over the TP.In terms of ecosystem zones,on the annual scale,in IIAB1 in the southeast of the TP and IB1 in the middle of the TP,IID1 in the western edge of the TP,ID1 in the northwest of the TP,and IID2 in the northern part of the TP,snow-albedo feedback has a great contribution to the EDW in these subregions.Except for IID2,these subregions have higher annual snow cover.On the seasonal scale,snow-albedo feedback has different importance in different subregions,in spring and autumn,snow-albedo feedback also contributed to the negative EDW in IC1 and some subregions.