| The analysis of terrestrial water storage change on the Tibetan Plateau is of great significance to the protection of water resources and has a vital impact on the ecology and economy of surrounding countries and regions.The water cycle system of the Tibetan Plateau has changed greatly in recent years,affected by global climate warming.The Tibetan Plateau is sparsely populated and covered with glaciers and permafrost.Due to the influence of landform and lack of various meteorological measured data,the large-scale planning of terrestrial water storage is difficult on the Tibetan Plateau.This study on terrestrial water storage change on the Tibetan Plateau has profound practical significance for China and other countries around Southeast Asia to reply environmental and climate change.The emergence of GRACE makes it possible to analyze the terrestrial water storage change on the Tibetan Plateau.Some progress has been made in the inversion of terrestrial water storage by gravity satellite,which has unique advantages compared with traditional monitoring methods.Based on the time-varying gravity data provided by GRACE satellite and GRACE-FO satellite during 2002-2019,this work uses Mascon method to calculate the change of terrestrial water storage,combined with lake water storage,glacial meltwater,soil moisture and permafrost,calculates groundwater storage according to the principle of water balance,and analyzes the influencing factors of terrestrial water storage change in six subregions of the Tibetan Plateau.Based on the analysis of the temporal and spatial distribution characteristics of various factors by using trend analysis method,Mann-Kendall trend test,empirical method decomposition and component analysis,the temporal and spatial variation mechanism of terrestrial water storage in each region is explored.This work makes up for the deficiency of quantitative calculation of various factors of terrestrial water storage on the Tibetan Plateau during 2002-2019,and reveals the spatial distribution mechanism of various factors and their impact on the change of terrestrial water storage.The main results are as follows.(1)The variation trends of terrestrial water storage in different regions of the Tibetan Plateauare:3.87±0.11 Gt/a,-0.39±0.13 Gt/a,1.51±0.08 Gt/a,-1.81 ±0.41 Gt/a,-6.23±0.34 Gt/a and 2.41±0.12 Gt/a,showing the characteristics of "increase in the north and decrease in the south" during 2002-2019.Using empirical mode decomposition method to analyze their trends,it is believed that IMF2 can separate the annual signal,and the residual trend is more consistent with linear trend.The terrestrial water storage on the inner Tibetan Plateau showed a significant downward trend around 2015,and then increased significantly.(2)The changes in soil moisture calculated by GLDAS are relatively close in amplitude,but their trends are quite different.The soil moisture in the southern part of the inner Tibetan Plateau has the largest decrease of-2.10±0.13 Gt/a,followed by the Brahmaputra River Basin,decreased as-1.94±0.25 Gt/a.Changes in lake water storage have a greater impact on the inner Tibetan Plateau.The southern part of the inner Tibetan Plateau has the largest downward trend,as 3.33±0.57 Gt/a,followed by the northern part of the inner Tibetan Plateau,as 2.62±0.22 Gt/a.Glacial meltwater is concentrated in the southeastern Tibetan Plateau and the Brahmaputra River Basin.Glacier’s spatial distribution characteristics are highly related to the reduction of terrestrial water storage,and the glacial meltwater in the Brahmaputra River Basin is the most serious in all subregions.The decrease trend of permafrost is mainly concentrated on the inner Tibetan Plateau and the Qaidam Basin.According to the principle of water balance,the changes of groundwater storage in each region are calculated,the results show that in the north,west of the inner Tibetan Plateau and Qaidam Basin have increased significantly.(3)This work quantifies the factors that contributed the most to the change of terrestrial water storage in each region,the groundwater storage and lake water storage in the northern part of the inner Tibetan Plateau contributed the most,accounting for 40%and 37%;the contribution rate of lake water storage in the southern part of the inner Tibetan Plateau is 47%;the contribution rate of groundwater in the west of the inner Tibetan Plateau is 40%;39%and 38%contribution of decrease trend of terrestrial water storage from glacial meltwater and soil moisture are found on the southeastern Tibetan Plateau;56%contribution to the decreasing trend from glacial meltwater is found in the Brahmaputra River Basin;groundwater storage change contributes 74%in Qaidam Basin. |
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