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首页> 外文期刊>Journal of hydrometeorology >An observational analysis and evaluation of land surface model accuracy in the Nebraska Sand Hills
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An observational analysis and evaluation of land surface model accuracy in the Nebraska Sand Hills

机译：内布拉斯加州沙丘的地表模型准确性的观测分析和评估

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In this study, the influence of subsurface water on the energy budget components of three locations with heterogeneous land surfaces in the Nebraska Sand Hills are examined through observations and use of the Noah land surface model (LSM). Observations of the four primary components of the surface energy budget are compared for a wet interdunal meadow valley, a dry interdunal valley, and a dunal upland location. With similar atmospheric forcing at each site, it was determined that differences in the partitioning of the mean diurnal net radiation (R-net) existed among the three locations due to the influence of varied soil moisture and vegetation through the year. At the wet valley, observations indicated that almost 65% of the mean daily peak R-net was used for latent heating, due to the relatively higher soil moisture content resulting from an annual upward gradient of subsurface water and denser vegetation. In sharp contrast, the dunal upland site yielded only 21% of the mean daily peak R-net going to latent heating, and a greater mean diurnal soil heat flux with typically drier soils and sparser vegetation than at the wet valley. The dry valley partition of the peak R-net fell between the wet valley and dunal upland site, with approximately 50% going to sensible heating and 50% toward latent heating. In addition to the observational analysis, an uncoupled land surface model was forced with the observations from each site to simulate the energy budgets, with no tuning of the model's fundamental equations and with little adjustment of the model parameters to improve results. While the model was able to reasonably simulate the mean diurnal and annual energy budget components at all locations, in most instances with root-mean-square errors within 20%-25% of the observed values, the lack of explicit treatment of subsurface water within the model limited predictability, particularly at the wet valley site. For instance, only 25% of the peak mean diurnal R-net went toward latent heating in the model simulation of the wet valley, compared to 65% as estimated by observations. Model evaluation statistics are presented to document the land surface model's ability to capture the annual and mean diurnal variations in the surface energy budget terms at the dry valley and dunal upland sites, but the absence of subsurface water results in large errors in the wet valley simulation. From these results, a case is made for the future inclusion of the explicit treatment of subsurface water within the Noah LSM to better approximate the prediction of the surface energy budget in such environments.
机译：在这项研究中，通过观察和使用诺亚陆面模型（LSM），研究了地下水对内布拉斯加州沙丘内三个具有非均质陆面位置的能量收支构成的影响。比较了湿润的跨际草甸谷，干燥的跨际谷和地面高地位置对地表能量收支的四个主要组成部分的观察结果。在每个地点的大气强迫相似的情况下，可以确定，由于一年中土壤水分和植被的变化，三个地点之间的平均日净辐射（R-net）的分配存在差异。在湿谷，观察表明，由于地下水的年度向上梯度和茂密的植被导致土壤水分含量相对较高，因此平均每日峰值R-net的近65％用于潜热。与之形成鲜明对比的是，沙丘高地仅产生潜热的平均每日峰值R-net的21％，并且在通常较干燥的土壤和稀疏植被的情况下，平均日热通量要大于湿谷。高峰R-net的干谷分配区位于湿谷和沙丘高地之间，其中约50％用于显热，而50％用于潜热。除了观测分析外，还需要对每个站点的观测结果进行非耦合地表模型模拟，以模拟能源预算，而无需调整模型的基本方程式，并且几乎不需调整模型参数来改善结果。尽管该模型能够合理模拟所有地点的平均日和年度能源预算组成部分，但在大多数情况下，均方根误差在观测值的20％-25％之内，但在此范围内缺乏对地下水的明确处理该模型限制了可预测性，特别是在湿谷地区。例如，在湿谷的模型模拟中，只有25％的峰值平均日R-net流向潜热，而观测值估计只有65％。提出了模型评估统计数据，以证明陆地表面模型能够捕获干旱谷地和沙地高地站点的表面能收支项的年度和平均日变化，但缺少地下水会导致湿谷模拟中的大误差。根据这些结果，有理由在将来将诺亚LSM内包括对地下水的显式处理，以更好地估算此类环境中地表能量收支的预测。

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