Abstract
As the “Water Tower of Asia” and “The Third Pole” of the world, the Qinghai–Tibet Plateau (QTP) shows great sensitivity to global climate change, and the change in its terrestrial water storage has become a focus of attention globally. Differences in multi-source data and different calculation methods have caused great uncertainty in the accurate estimation of terrestrial water storage. In this study, the Yarlung Zangbo River Basin (YZRB), located in the southeast of the QTP, was selected as the study area, with the aim of investigating the spatio-temporal variation characteristics of terrestrial water storage change (TWSC). Gravity Recovery and Climate Experiment (GRACE) data from 2003 to 2017, combined with the fifth-generation reanalysis product of the European Centre for Medium-Range Weather Forecasts (ERA5) data and Global Land Data Assimilation System (GLDAS) data, were adopted for the performance evaluation of TWSC estimation. Based on ERA5 and GLDAS, the terrestrial water balance method (PER) and the summation method (SS) were used to estimate terrestrial water storage, obtaining four sets of TWSC, which were compared with TWSC derived from GRACE. The results show that the TWSC estimated by the SS method based on GLDAS is most consistent with the results of GRACE. The time-lag effect was identified in the TWSC estimated by the PER method based on ERA5 and GLDAS, respectively, with 2-month and 3-month lags. Therefore, based on the GLDAS, the SS method was used to further explore the long-term temporal and spatial evolution of TWSC in the YZRB. During the period of 1948–2017, TWSC showed a significantly increasing trend; however, an abrupt change in TWSC was detected around 2002. That is, TWSC showed a significantly increasing trend before 2002 (slope = 0.0236 mm/month, p < 0.01) but a significantly decreasing trend (slope = −0.397 mm/month, p < 0.01) after 2002. Additional attribution analysis on the abrupt change in TWSC before and after 2002 was conducted, indicating that, compared with the snow water equivalent, the soil moisture dominated the long-term variation of TWSC. In terms of spatial distribution, TWSC showed a large spatial heterogeneity, mainly in the middle reaches with a high intensity of human activities and the Parlung Zangbo River Basin, distributed with great glaciers. The results obtained in this study can provide reliable data support and technical means for exploring the spatio-temporal evolution mechanism of terrestrial water storage in data-scarce alpine regions.
Highlights
Given that the spatial resolution of Gravity Recovery and Climate Experiment (GRACE)-derived terrestrial water storage change (TWSC) is 0.5◦ × 0.5◦, the TWSC estimated from ERA5 and Global Land Data Assimilation System (GLDAS) was interpolated to 0.5◦ × 0.5◦ based on the bilinear interpolation method to compare it with TWSC derived from GRACE
From 2003 to 2017 estimated by ERA5 and GLDAS with the PER method and the SS method, which were compared with the TWSC derived from GRACE
It can be seen that there is a large variability in TWSC estimated by different datasets and different methods, among which the trend of GLDAS-SS is most consistent with the results derived from GRACE
Summary
Terrestrial water storage refers to all forms of water stored at or below the surface, including surface water, groundwater, soil moisture, glaciers, lakes, forest canopy intercepted. Due to its significant impacts on hydrological and climatic systems, TWSC has been widely used to represent the spatial and temporal evolution characteristics of water balance at global and regional scales [3]. A large number of studies have revealed that TWSC plays an irreplaceable role in detecting the melting of glaciers and snow [4], characterizing the degradation of permafrost and the increase in the thickness of active layers [5], describing the changes in soil moisture and groundwater [6,7,8], and assessing extreme events such as droughts and floods [9,10]. The QTP has the third largest glacier area (about 91,822 km2 ) in the world and the greatest number and area of lakes in China (with a total area of more than 4.7 × 104 km2 ) [13], where about
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