Browsing by Author "Chang, Le"

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    Satellite-observed monthly glacier and snow mass changes in southeast Tibet : implication for substantial meltwater contribution to the Brahmaputra
    (2020) Yi, Shuang; Song, Chunqiao; Heki, Kosuke; Kang, Shichang; Wang, Qiuyu; Chang, Le
    High-Asia glaciers have been observed to be retreating the fastest in the southeastern Tibet Plateau (SETP), where vast numbers of glaciers and amounts of snow feed the streamflow of the Brahmaputra, a transboundary river linking the world's two most populous countries, China and India. However, the low temporal resolutions in previous observations of glacier and snow (GS) mass balance obscured the seasonal accumulation–ablation variations, and their modelling estimates were divergent. Here we use monthly satellite gravimetry observations from August 2002 to June 2017 to estimate GS mass variation in the SETP. We find that the “spring-accumulation-type” glaciers and snow in the SETP reach their maximum in May. This is in stark contrast to seasonal variations in terrestrial water storage, which is controlled by summer precipitation and reaches the maximum in August. These two seasonal variations are mutually orthogonal and can be easily separated in time-variable gravity observations. Our GS mass balance results show a long-term trend of -6.5±0.8 Gt yr^-1 (or 0.67±0.08 m w.e. yr^-1) and annual mass decreases ranging from -49.3 to -78.3 Gt with an average of -64.5±8.9 Gt in the SETP between August 2002 and June 2017. The contribution of summer meltwater to the Brahmaputra streamflow is estimated to be 51±9 Gt. This result could help to resolve previous divergent modelling estimates and underlines the importance of meltwater to the Brahmaputra streamflow. The high sensitivity between GS melting and temperature on both annual and monthly scales suggests that the Brahmaputra will suffer from not only changes in total annual discharge but also an earlier runoff peak due to ongoing global warming.
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    Using GRACE data to study the impact of snow and rainfall on terrestrial water storage in Northeast China
    (2020) Qian, An; Yi, Shuang; Chang, Le; Sun, Guangtong; Liu, Xiaoyang
    Water resources are important for agricultural, industrial, and urban development. In this paper, we analyzed the influence of rainfall and snowfall on variations in terrestrial water storage (TWS) in Northeast China from Gravity Recovery and Climate Experiment (GRACE) gravity satellite data, GlobSnow snow water equivalent product, and ERA5-land monthly total precipitation, snowfall, and snow depth data. This study revealed the main composition and variation characteristics of TWS in Northeast China. We found that GRACE provided an effective method for monitoring large areas of stable seasonal snow cover and variations in TWS in Northeast China at both seasonal and interannual scales. On the seasonal scale, although summer rainfall was 10 times greater than winter snowfall, the terrestrial water storage in Northeast China peaked in winter, and summer rainfall brought about only a sub-peak, 1 month later than the maximum rainfall. On the interannual scale, TWS in Northeast China was controlled by rainfall. The correlation analysis results revealed that the annual fluctuations of TWS and rainfall in Northeast China appear to be influenced by ENSO (EI Niño-Southern Oscillation) events with a lag of 2-3 years. In addition, this study proposed a reconstruction model for the interannual variation in TWS in Northeast China from 2003 to 2016 on the basis of the contemporary terrestrial water storage and rainfall data.