A Groundwater and Runoff Formulation for Weather and Climate Models
A Groundwater and Runoff Formulation for Weather and Climate Models
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天气和气候模型的地下水和径流公式
DOI：
10.1029/2017ms001260
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发表时间：
2018
影响因子：
6.8
通讯作者：
Lukas Strebel
中科院分区：
文献类型：
--
作者：
L. Schlemmer;C. Schär;D. Lüthi;Lukas Strebel
土壤湿度改变了大气的状态，因此在气候系统中起着重要作用。其空间分布受下伏地形的强烈调节。然而，目前在大多数大气和气候模型中，土壤水分的垂直输送，特别是土壤柱底部地下水径流的产生，都是以一种粗糙的方式处理的。这可能会导致中纬度地区夏季近地表温度出现较大偏差，届时土壤可能会干涸。在这里，我们提出了一个地下水和径流形成的新公式。它基于理查兹方程，考虑饱和含水层，包括与坡度相关的地下水排放，并能够对底层地形进行亚网格尺度的处理。所提出的数值实现确保了土柱中水通量的物理一致性处理，使用了通量校正输运方法的思想。在气候模式（CCLM）小尺度模拟联盟（COSMO）区域气候模式的陆地表面模式TERRA_ML中实现了这一公式，并在理想和实际情况模拟中得到了验证。理想化的模拟证明了土柱底部的下边界条件的重要作用，并显示了物理上有意义的饱和区补给和排泄。根据选定站点的测量结果进行验证，表明土壤含水量的季节性演变有所改善。最后，欧洲的十年气候模拟显示了地下水在大陆尺度和山区分布的真实表现，地表潜热通量的年循环得到改善，因此半干旱地区近地表温度的长期偏差减少。
Soil moisture modifies the state of the atmosphere and thus plays a major role in the climate system. Its spatial distribution is strongly modulated by the underlying orography. Yet the vertical transport of soil water and especially the generation of groundwater runoff at the bottom of the soil column are currently treated in a crude way in most atmospheric and climate models. This potentially leads to large biases in near‐surface temperatures during midlatitude summertime conditions, when the soils may dry out. Here we present a new formulation for groundwater and runoff formation. It is based on Richards equation, allows for saturated aquifers, includes a slope‐dependent groundwater discharge, and enables a subgrid‐scale treatment of the underlying orography. The proposed numerical implementation ensures a physically consistent treatment of the water fluxes in the soil column, using ideas from flux‐corrected transport methodologies. An implementation of this formulation into TERRA_ML, the land surface model of the regional climate model of the COnsortium for Small‐scale MOdeling (COSMO) in CLimate Mode (CCLM), is validated both in idealized and real‐case simulations. Idealized simulations demonstrate the important role of the lower boundary condition at the bottom of the soil column and display a physically meaningful recharge and discharge of the saturated zone. Validation against measurements at selected stations shows an improved seasonal evolution of soil water content. Finally, decade‐long climate simulations over Europe exhibit a realistic representation of the groundwater distribution across continental scales and mountainous areas, an improved annual cycle of surface latent heat fluxes, and as a consequence reductions of long‐standing biases in near‐surface temperatures in semiarid regions.
影响因子：
5.2
作者：
B. Gallego-Elvira;C. Taylor;P. Harris;D. Ghent;K. Veal;S. Folwell
通讯作者：
B. Gallego-Elvira;C. Taylor;P. Harris;D. Ghent;K. Veal;S. Folwell
影响因子：
5.1
作者：
Kotlarski, S.;Keuler, K.;Wulfmeyer, V.
通讯作者：
Wulfmeyer, V.