STEMMUS-UEB v1.0.0: integrated modeling of snowpack and soil water and energy transfer with three complexity levels of soil physical processes
STEMMUS-UEB v1.0.0: integrated modeling of snowpack and soil water and energy transfer with three complexity levels of soil physical processes
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DOI：
10.5194/gmd-14-7345-2021
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发表时间：
2021-11
影响因子：
5.1
通讯作者：
Lianyu Yu;Yijian Zeng;Z. Su
中科院分区：
文献类型：
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作者：
Lianyu Yu;Yijian Zeng;Z. Su
抽象。积雪通过其对地表覆盖度和粗糙度及其隔热性能的影响，对一个地区的水文和地表能量条件产生深远的影响。积雪、土壤水动力学以及积雪与下伏土壤层耦合的模拟已被广泛报道。然而，考虑积雪效应的液-气-气耦合流动机理尚未得到详细研究。在这项研究中，我们将积雪效应（犹他州能量平衡积雪模型，UEB）纳入一个通用的建模框架（非饱和土壤冻融过程中能量、质量和动量的同时转移，STEMMUS-FT），即，茎-UEB。它考虑了土壤水分和能量传递物理学的三个复杂程度（基本耦合，先进的耦合水和热传递，最后明确考虑气流，分别称为BCD，ACD和ACD-空气）。然后，我们利用现场观测和数值试验研究积雪对土壤水热传输的影响与上述模式的复杂性。结果表明，有积雪的模式可以再现降水事件后地面湿度的突然增加，而无积雪的模式则不能再现。BCD模式有高估陆面潜热通量的倾向。ACD和ACD-空气模型大大降低了这种高估。与考虑积雪的模拟相比，无雪模拟由于忽略了雪的升华作用而导致LE值减小。冬季降水事件后，地表冰升华、雪升华和表层土壤水分增加是导致LE增强的主要原因。上述三个来源的相对作用取决于降水的时间和规模以及降水前的土壤热液状况。简单的BCD模型不能提供一个真实的传质通量分区。ACD模型通过其对蒸汽流、对水流的热效应和积雪的物理考虑，可以确定不同组分（例如，热的或等温的液体和蒸气流）与总传质通量之比。在ACD-空气模型中，各组分（主要是等温液流和汽流）对传质的相对贡献在土壤解冻期间发生了显著变化。结果发现，积雪不仅影响土壤表面水分条件（表面冰和土壤水含量在液相中）和能量相关的状态（冰，LE），但也地下土壤液体和蒸汽流的传输模式。
Abstract. A snowpack has a profound effect on the hydrology and surface energy conditions of an area through its effects on surface albedo and roughness and its insulating properties. The modeling of a snowpack, soil water dynamics, and the coupling of the snowpack and underlying soil layer has been widely reported. However, the coupled liquid–vapor–air flow mechanisms considering the snowpack effect have not been investigated in detail. In this study, we incorporated the snowpack effect (Utah energy balance snowpack model, UEB) into a common modeling framework (Simultaneous Transfer of Energy, Mass, and Momentum in Unsaturated Soils with Freeze-Thaw, STEMMUS-FT), i.e., STEMMUS-UEB. It considers soil water and energy transfer physics with three complexity levels (basic coupled, advanced coupled water and heat transfer, and finally explicit consideration of airflow, termed BCD, ACD, and ACD-air, respectively). We then utilized in situ observations and numerical experiments to investigate the effect of snowpack on soil moisture and heat transfer with the abovementioned model complexities. Results indicated that the proposed model with snowpack can reproduce the abrupt increase of surface albedo after precipitation events while this was not the case for the model without snowpack. The BCD model tended to overestimate the land surface latent heat flux (LE). Such overestimations were largely reduced by ACD and ACD-air models. Compared with the simulations considering snowpack, there is less LE from no-snow simulations due to the neglect of snow sublimation. The enhancement of LE was found after winter precipitation events, which is sourced from the surface ice sublimation, snow sublimation, and increased surface soil moisture. The relative role of the mentioned three sources depends on the timing and magnitude of precipitation and the pre-precipitation soil hydrothermal regimes. The simple BCD model cannot provide a realistic partition of mass transfer flux. The ACD model, with its physical consideration of vapor flow, thermal effect on water flow, and snowpack, can identify the relative contributions of different components (e.g., thermal or isothermal liquid and vapor flow) to the total mass transfer fluxes. With the ACD-air model, the relative contribution of each component (mainly the isothermal liquid and vapor flows) to the mass transfer was significantly altered during the soil thawing period. It was found that the snowpack affects not only the soil surface moisture conditions (surface ice and soil water content in the liquid phase) and energy-related states (albedo, LE) but also the transfer patterns of subsurface soil liquid and vapor flow.