The reservoir of soil water is exchanged with the atmosphere through evaporative processes, which are mediated via vegetation through transpiration. Carbon uptake is closely coupled to transpiration, and most process‐based models link transpiration and photosynthesis explicitly. Here, we evaluate the simulation of water and carbon fluxes in forested areas of North America using point‐based simulations of the Community Land Model version 5 (CLM5) with Soil Moisture Active/Passive (SMAP) satellite derived soil moisture measurements and in situ measurements at eight Fluxnet and two United States Climate Research Network (CRN) sites. Compared to observations, there is a broad site‐to‐site variability in simulated soil moisture, with some sites exhibiting wet biases and others dry biases. The bias sign does not depend on ecosystem or other environmental drivers such as radiation and temperature. Compared to Fluxnet latent heat (LH) and gross primary production (GPP) flux tower observations, simulated LH flux biases at deciduous broadleaf forests are linked with soil moisture biases, and the model captures the observed seasonal cycle and parabolic seasonal relationship with soil moisture. The parabolic shape is driven by high soil moisture and low LH fluxes in June, peak LH and drier soil conditions in July, followed by further soil moisture drawdown in August. GPP is underestimated at most sites, and the model exhibits a linear relationship between soil moisture and GPP. Because the photosynthesis parameterizations are similar in most Earth system models, further model development that incorporates observations and observed relationships is needed to accurately capture the GPP‐soil moisture relationship.

中文翻译：

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地表模型能否捕获温带至北方森林水和碳通量的土壤水分控制观测值？

土壤水库通过蒸发过程与大气交换，而蒸发过程是通过蒸腾作用通过植被介导的。碳的吸收与蒸腾作用密切相关，大多数基于过程的模型都将蒸腾作用与光合作用明确地联系在一起。在这里，我们使用基于土壤湿度主动/被动（SMAP）卫星得出的土壤湿度测量值和原位测量值的社区土地模型第5版（CLM5）的点模拟，评估了北美林区的水和碳通量模拟。在八个Fluxnet和两个美国气候研究网络（CRN）站点。与观测值相比，模拟土壤湿度在不同地点之间存在很大的差异，其中一些地点表现出湿偏差，而另一些地方表现出干偏差。偏差符号不取决于生态系统或其他环境驱动因素，例如辐射和温度。与Fluxnet潜热（LH）和总初级生产量（GPP）的通量塔观测值相比，在落叶阔叶林中模拟的LH通量偏差与土壤湿度偏差相关，并且该模型捕获了观测到的季节性周期和与土壤水分的抛物线季节性关系。抛物线的形状是由6月的高土壤湿度和低LH通量，7月的LH高峰和较干燥的土壤条件驱动的，然后是8月土壤水分进一步下降的驱动力。GPP在大多数站点都被低估了，该模型表现出土壤水分与GPP之间的线性关系。由于大多数地球系统模型中的光合作用参数设置相似，