High latitude regions, including the circumpolar boreal biome, are experiencing important changes in the availability of usable surface water because of climate change. In this context, an adequate representation of the land-atmosphere interaction is critical to ensure optimal management of current and future water resources, forest management, and climate prediction. However, the task is particularly intricate in high-latitude boreal forest, as land surface model faces several challenges due to the unique environmental conditions and ecological characteristics. The objective of this study is to quantify the impact of forest landscape heterogeneity, specifically stand leaf-area index (LAI), soil texture, and drainage regime, on surface water and energy balance in a small boreal high-latitude sub-catchment. To this end, hydrometeorological conditions at seventeen 20×20 m plots in a 1-km boreal forest sub-basin are simulated using the Canadian Land Surface Scheme (CLASS), a land surface model, at the point scale. The subplot-scale soil texture, drainage regime, and vegetation characteristics and type are based as closely as possible on field measurements and observations for the 17 plots. The model-driven experiment comprises two sets of simulations using CLASS, each employing the same model setup and run for the 17 experimental plots. The main set employs meteorological forcing from a local micrometeorological tower within the sub-basin to investigate the plot-to-plot variability of albedo, energy fluxes, and soil state variables. A second set of simulations is conducted using meteorological forcing from the ERA5-Land reanalysis, which spans from 1986 to 2022. This data provides a longer time series, enabling a more accurate representation of the interannual climatic variability in the sub-basin. The results of the main and secondary sets of CLASS simulations are used to assess the plot-to-plot and temporal variability of several key hydrometeorological variables by calculating a monthly spread. In brief, the following conclusions and broader implications can be drawn from the findings: i) The simulated total annual evapotranspiration remains relatively uniform between plots despite notable variation in its partitioning from plot to plot. ii) In the presence of a full snowpack, the albedo exhibits substantial heterogeneity at the subplot scale, linked to the canopy's LAI. iii) Local soil properties, drainage regime, and vegetation structure and type exhibit substantial influence on the plot-to-plot variability in soil water content. iv) When parameterized with localized observations and measurements, CLASS can represent and be responsive to the complex dynamics of energy and water fluxes at the plot scale within the heterogeneous surface of boreal forests.

中文翻译：

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森林冠层异质性对地块尺度水文气象变量的影响 - 根据加拿大陆地表面计划在潮湿的北方森林进行的实验的见解


由于气候变化，包括环极地北方生物群落在内的高纬度地区可用地表水的供应量正在经历重大变化。在这种情况下，充分表征陆地-大气相互作用对于确保当前和未来水资源、森林管理和气候预测的最佳管理至关重要。然而，在高纬度北方森林中，由于独特的环境条件和生态特征，地表模型面临着一些挑战，因此这项任务尤其复杂。本研究的目的是量化森林景观异质性，特别是林分叶面积指数（LAI）、土壤质地和排水状况对小型北方高纬度子流域地表水和能量平衡的影响。为此，利用地表模型加拿大地表方案（CLASS）在点尺度上模拟了1 km北方森林子流域中17个20×20 m样地的水文气象条件。子地块规模的土壤质地、排水状况以及植被特征和类型尽可能地基于 17 个地块的现场测量和观察。模型驱动实验包括两组使用 CLASS 的模拟，每组模拟均采用相同的模型设置并运行 17 个实验地块。主数据集利用子流域内当地微气象塔的气象强迫来研究反照率、能量通量和土壤状态变量的地块间变化。第二组模拟是利用 ERA5-Land 再分析（从 1986 年到 2022 年）的气象强迫进行的。 该数据提供了更长的时间序列，能够更准确地表示子流域的年际气候变化。主要和次要 CLASS 模拟集的结果用于通过计算月度分布来评估几个关键水文气象变量的图间变化和时间变化。简而言之，从研究结果中可以得出以下结论和更广泛的含义：i）尽管地块之间的划分存在显着差异，但地块之间的模拟年度总蒸散量仍然相对均匀。 ii) 在存在完整积雪的情况下，反照率在次要地块尺度上表现出显着的异质性，与冠层的 LAI 相关。 iii) 当地土壤性质、排水状况以及植被结构和类型对土壤含水量的地块间变异性具有重大影响。 iv) 当通过局部观测和测量进行参数化时，CLASS 可以表示并响应北方森林异质表面内地块尺度的能量和水通量的复杂动态。