As a component of the surface heat budget, surface solar radiation (SSR) is the primary source of energy for the earth surface. It controls both water and energy exchanges between land surface and overlying atmosphere and is thus a major forcing for the land surface models, hydrological models, and ecological models (L.
Permafrost degradation poses an increasingly serious threat of glacial lake outburst floodings (GLOFs) in the Tibetan Plateau. It is therefore of great practical significance to analyze the freeze-thaw state in moraine dams and associated impacts on dam stability. We simulated the soil temperature of the Longbasaba moraine dam based on the heat transfer module of COMSOL Multiphysics. The results show that the soil temperature of the moraine dam can be adequately simulated using the COMSOL Multiphysics heat transfer module and the simulated temperature values are generally consistent with the observed trends, yielding root mean square errors (RMSEs) less than 1.58 and Nash-Sutcliffe efficiency coefficients (NSEs) between 0.66 and 0.93. The average annual increase of the active layer depth was 0.026 m/a from 1959 to 2020. The buried ice inside the moraine dam was evidently melting and the maximum buried ice thawing depth under scenarios SSP1-2.6, SSP2-4.5, and SSP5-8.5 in CMIP6 (Coupled Model Intercomparison Project Phase 6) is expected to be 11.3 m, 18.4 m, and 23.5 m, respectively, by the end of the century, which indicates a continuous deterioration of the moraine dam stability.
The lower elevation limit for permafrost on the northern slopes of the Himalayas is considered to be 5,100-5,300 m above sea level (a.s.l.) (Gruber, 2012;Zou et al., 2017); and there are thousands of moraine-dammed lakes above this limit (
Downward solar radiation (DSR) and air temperature (Ta) have significant influences on the thermal state of frozen ground. These parameters are also important forcing terms for physically based land surface models (LSMs). However, the quantitative influences of inaccuracies in DSR and Ta products on simulated frozen ground temperatures remain unclear. In this study, three DSR products (CMFD‐SR, Tang‐SR, and GLDAS‐SR) and two Ta products (CMFD‐Ta and GLDAS‐Ta) were used to force an LSM model in an alpine watershed in Northwest China, to investigate the sensitivity of simulated ground temperatures to different DSR and Ta products. Compared to a control model (CTRL) forced by in situ observed DSR, ground temperatures simulated by the experimental model forced by GLDAS‐SR are obviously decreased because GLDAS‐SR is much lower than in situ observations. Instead, simulation results in models forced by CMFD‐SR and Tang‐SR are much closer to those of CTRL. Ta products led to significant errors in simulated ground temperatures. In conclusion, both CMFD‐SR and Tang‐SR could be used as good alternatives to in situ observed DSR for forcing a model, with acceptable errors in simulation results. However, more care need to be paid for models forced by Ta products instead of Ta observations, and conclusions should be carefully drawn.
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