Improved modeling of snow and glacier melting by a progressive two‐stage calibration strategy with GRACE and multisource data: How snow and glacier meltwater contributes to the runoff of the Upper Brahmaputra River basin?

Abstract

Snow and glacier melting and accumulation are important processes of the hydrological cycle in the cryosphere, e.g., high‐mountain areas. Glaciers and snow cover respond to climate change notably over the Tibetan Plateau (TP) as the Earth's Third Pole where complex topography and lack of ground‐based observations result in knowledge gaps in hydrological processes and large uncertainties in model output. This study develops a snow and glacier melt model for a distributed hydrological model (Coupled Routing and Excess Storage model, CREST) using the Upper Brahmaputra River (UBR) basin in the TP as a case study. Satellite and ground‐based precipitation and land surface temperature are jointly used as model forcing. A progressive two‐stage calibration strategy is developed to derive model parameters, i.e., (1) snow melting processes (stage I) and (2) glacier melting and runoff generation and routing using multisource data (stage II). Stage‐I calibration is performed using the MODIS snow cover area (SCA) product and a blending snow water equivalent (SWE) product combined with partial in situ measurements. Stage‐II calibration is based on Gravity Recovery and Climate Experiment (GRACE) satellite‐derived total water storage (TWS) changes and streamflow observed at a gauging station of the lower reach of the UBR. Results indicate that the developed two‐stage calibration method provides more reliable streamflow, snow (both SCA and SWE), and TWS change simulations against corresponding observations than commonly used methods based on streamflow and/or SCA performance. The simulated TWS time series shows high consistency with GRACE counterparts for the study period 2003–2014, and overestimated melting rates and contributions of glacier meltwater to runoff in previous studies are improved to some degree by the developed model and calibration strategy. Snow and glacier runoff contributed 10.6% and 9.9% to the total runoff, and the depletion rate of glacier mass was ∼ −10 mm/a (∼ −2.4 Gt/a, Gt/a is gigaton (km3 of water) per year) over the UBR basin during the study period. This study is valuable in examining the impacts of climate change on hydrological processes of cryospheric regions and providing an improved approach for simulating more reliable hydrological variables over the UBR basin and potentially similar regions globally.

Quantitative Analysis of Terrestrial Water Storage Changes Under the Grain for Green Program in the Yellow River Basin

“…The GLDAS 2.1 soil moisture, which had been validated using observations (Figure S4), was used because the observations were only up to 2010. Snow and glacier are important factors for the hydrological cycle in high‐mountain cryosphere (Chen et al, ), for example, the headwaters of the Yellow River. The north Tibetan Plateau, where the Yellow River originates, was found to show a significant increasing trend in TWSA by Long et al (), and the increase was mainly attributed to lake expansion from increased precipitation and glacier melting.…”

Understanding terrestrial water storage variations in northern latitudes across scales

“…Due to their global coverage and independence from surface conditions, the data represent a unique opportunity to quantify spatio-temporal variations of the Earth's water resources (Alkama et al, 2010;Werth et al, 2009). Therefore, GRACE data have been widely used to diagnose patterns of hydrological variability (Seo et al, 2010;Rodell et al, 2009;Ramillien et al, 2006;Feng et al, 2013), to validate and improve model simulations Güntner, 2008;Werth and Güntner, 2010;Chen et al, 2017;Eicker et al, 2014;Girotto et al, 2016;Schellekens et al, 2017), and to enhance our understanding of the water cycle on regional to global scales (Syed et al, 2009;Felfelani et al, 2017).…”

“…So far, only a few models used to assess hydrological processes on continental to global scales are constrained by observations, and if so, they are mainly calibrated against the observed discharge of large river basins (Long et al, 2015;Döll et al, 2015). Recently, several studies showed the benefits of additionally including GRACE TWS data in model calibration (Werth and Güntner, 2010;Xie et al, 2012;Chen et al, 2017) or by means of data assimilation Forman et al, 2012;Kumar et al, 2016). However, although these approaches improve model simulations, they do not reduce the uncertainty in the partitioning of TWS due to the parameter equifinality problem (Güntner, 2008).…”

Observed radiative cooling over the Tibetan Plateau for the past three decades driven by snow cover‐induced surface albedo anomaly

“…Compared with other midlatitude regions, seasonal snow cover over the TP has unique features in terms of global snow cover map because of the high mountains and it has vital water storage properties [ Pu et al ., ]. With an accelerated change in the environment on the TP caused by climate change [ Zhong et al ., ], including anomalies in warming trend [ Duan and Xiao , ], advanced vegetation green‐up dates [ Zhang et al ., ], enhanced evaporative cooling [ Shen et al ., ], and shrinking glaciers [ Chen et al ., ; Long et al ., ; Yao et al ., ] in most regions over the TP, the status of snow cover and its contribution to the Earth climate system remain unknown.…”