Simulation and assessment of soil temperature and moisture in seasonally frozen soil regions of the Tibetan Plateau based on SHAW model北大核心CSCD

In recent years，more and more attention has been paid to the problem of the cryosphere changes on the Tibetan Plateau，and it has gradually become a hot issue for scholars. Known as the“water tower of Asia”，the Tibetan Plateau is the source of many major rivers in Asia. Under the combined influence of climate change and human activities，water resources on the Tibetan Plateau have undergone profound changes，especially soil water，as an important component of water resources，which plays an important role in regulating vegetation and crop growth，rainfall and runoff. However，global warming leads to the degradation of permafrost and seasonal? ly frozen soil，which affects the original water cycle process and the spatial and temporal pattern of water re? sources by changing the properties of soil water storage and water transport. In the Tibetan Plateau，where there are few data，it is difficult to directly study the soil water cycle process under freezing-thawing by using original data. Therefore，it is an important means to simulate the variation characteristics of soil water and temperature under freezing-thawing in seasonally frozen soil regions of the Tibetan Plateau by using coupling model of soil water and heat. Aiming at the key problem of the difference of soil temperature and moisture characteristics in typical seasonally frozen soil regions under different meteorological conditions，this paper simulated the charac? teristics of soil moisture and temperature change in Maqu，Naqu（Nagqu）and Shiquanhe from 2017 to 2018 by using SHAW（Simultaneous Heat and Water）model and three soil moisture characteristic curve models. The simulation effect and variation characteristics of soil moisture and temperature under different meteorological conditions were analyzed，and the influence of soil moisture characteristic curve model on the simulation effect was studied. The results show that SHAW model can well simulate the temporal variation and vertical distribu? tion of soil temperature and moisture under different meteorological conditions. The simulation effect of soil tem? perature is better than that of soil moisture. The average NSE，R2 and RMSE of soil temperature are 0. 88，0. 96 and 2. 20 ℃，respectively. The mean NSE，R2 and RMSE of soil moisture are 0. 60，0. 72 and 0. 03 m3·m-3，respec? tively. In terms of different meteorological conditions，the simulation effect of soil temperature in relatively dry region was significantly better than that in humid region，while the simulation effect of soil water in relatively hu? mid region was significantly better than that in arid region. From different depths in soil，the simulation effect of soil temperature decreases gradually with the increase of depth，while the simulation effect of soil moisture in the middle and lower layers is better than that in the surface layer. From the view of different soil moisture character? istic curve models，different soil water characteristic curve models have no significant effect on soil temperature simulation effect，but there are significant differences in soil moisture simulation effect. In addition，there are great differences and uncertainties in simulating soil temperature and moisture in different freezing-thawing stag? es. With the increasing trend of climate warming，permafrost and seasonally frozen soil on the Tibetan Plateau may continue to degrade，may change the current water resources pattern，resulting in frequent extreme weather events. Therefore，from the perspective of numerical simulation，this paper verified the applicability of soil moisture and heat coupling model in soil temperature and moisture simulation under different meteorological con? ditions，revealed the influence of precipitation and temperature on soil temperature and moisture simulation at different depths in seasonally frozen soil regions，and analyzed the differences in simulation effects of different soil moisture characteristic curve models. The results provide reference for the study of soil water resources vari? ation under freezing-thawing conditions. © 2023 Chinese Journal of General Practitioners. All rights reserved.