Simulation of freeze‐thaw cycles in a general circulation model land surface scheme
Simulation of freeze‐thaw cycles in a general circulation model land surface scheme
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DOI：
10.1029/97jd03630
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发表时间：
1998-05
影响因子：
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通讯作者：
A. Slater;A. Pitman;C. Desborough
中科院分区：
文献类型：
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作者：
A. Slater;A. Pitman;C. Desborough
利用从前苏联四个地点收集的观测气象数据，对一个设计用于气候模式的陆面方案进行了为期6年的整合。利用实测的土壤水分和冻结锋数据，验证了模型对各站6年冻融循环的模拟。该模型能够模拟的一般特征的季节性冻融循环的所有站点的所有年份。在模拟春季期间的最佳近似表面交换（BASE）的问题：该模型模拟过量积累的液体土壤水分在春季和未能匹配的观测时间的总冻结和总解冻。大多数问题都与导水率的参数化有关，当对导水率进行修改时，模型能够更准确地模拟土壤有效水分。此外，它表明，包括冻土参数化是必要的，以捕捉土壤水分的广泛的季节性周期，不考虑冻土的影响可以延伸到春季解冻期以外。为了进一步改进模拟，可能有必要模拟低温扰动（包括大孔隙）、冻结锋、冰透镜和其他冰缘过程的影响。考虑到气候模式的空间分辨率、陆面方案的垂直分辨率（1-5层）以及缺乏适当的观测数据，即使这些过程可以参数化，模拟的质量也不可能提高到足以保证额外的计算费用。
Using observed meteorological data collected from four sites in the former Soviet Union, a land surface scheme designed for use in climate models was integrated for 6 years. Using observed available soil moisture and freezing front data, the model simulation of freeze-thaw cycles over the 6 years for each station was validated. The model was able to simulate the general characteristics of the seasonal freeze-thaw cycles for all stations for all years. There were problems in the simulation of the spring period by Best Approximation of Surface Exchanges (BASE): the model simulated excess accumulation of liquid soil moisture in spring and failed to match the observed timing of total freeze and total thaw. Most problems could be linked to the parameterization of hydraulic conductivity, and when this was modified, the model was able to simulate the available soil moisture more accurately. Moreover, it was shown that the inclusion of a frozen soil parameterization is necessary in order to capture the broad seasonal cycle of soil moisture and that the impact of not accounting for frozen soil can extend beyond the spring thaw period. To improve the simulations further, it may be necessary to model the effects of cryoturbation (including macropores), freezing fronts, ice-lensing and other periglacial processes. Given the spatial resolution of climate models, the vertical resolution of land surface schemes (1–5 layers), and the lack of suitable observed data, even if these processes could be parameterized, the quality of the simulations are unlikely to increase enough to warrant the additional computational expense.