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首页> 外文期刊>Frontiers in Digital Humanities >Surface Energy Balance Closure and Turbulent Flux Parameterization on a Mid-Latitude Mountain Glacier, Purcell Mountains, Canada
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Surface Energy Balance Closure and Turbulent Flux Parameterization on a Mid-Latitude Mountain Glacier, Purcell Mountains, Canada

机译：加拿大珀塞尔山中纬度山区冰川的表面能平衡封闭和湍流通量参数化

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In the majority of glacier surface energy balance studies, parameterisation rather than direct measurement is used to estimate one or more of the individual heat fluxes, with others, such as the rain and ground heat fluxes, often deemed negligible. Turbulent fluxes of sensible and latent heat are commonly parameterised using the bulk aerodynamic technique. This method was developed for horizontal, uniform surfaces rather than sloped, inhomogeneous glacier terrain, and significant uncertainty remains regarding the selection of appropriate roughness length values, and the validity of the atmospheric stability functions employed. A customised weather station, designed to measure all relevant heat fluxes, was installed on an alpine glacier over the 2014 melt season. Eddy covariance techniques were used to observe the turbulent heat fluxes, and to calculate site-specific roughness values. The obtained dataset was used to drive a point ablation model, and to evaluate the most commonly used bulk methods and roughness length schemes in the literature. Modelled ablation showed good agreement with observed rates at seasonal, daily, and sub-daily timescales, effectively closing the surface energy balance, and giving a high level of confidence in the flux observation method. Net radiation was the dominant contributor to melt energy over the season (65.2%), followed by the sensible heat flux (29.7%), while the rain heat flux was observed to be a significant contributor on daily timescales during periods of persistent heavy rain (up to 20% day-1). Momentum roughness lengths observed for the study surface (snow: 10-3.8 m; ice: 10-2.2 m) showed general agreement with previous findings, while the scalar values (temperature: 10-4.6 m; water vapour: 10-6 m) differed significantly from those for momentum, disagreeing with the assumption of equal roughness lengths. Of the three bulk method stability schemes tested, the functions based on the Monin-Obukhov length returned mean daily flux values closest to those observed, but displayed poor performance on sub-daily timescales, and periods of substantial flux overestimation.
机译：在大多数冰川表面能平衡研究中，使用参数化而非直接测量来估算一个或多个单独的热通量，而通常认为可以忽略不计的其他一些（如雨水和地面热通量）。显热和潜热的湍流通量通常使用整体空气动力学技术进行参数化。这种方法是为水平，均匀的表面而不是倾斜，不均匀的冰川地形开发的，在选择合适的粗糙度长度值以及所采用的大气稳定性函数的有效性方面仍然存在很大的不确定性。 2014年融化季节，在高山冰川上安装了专门用来测量所有相关热通量的气象站。涡度协方差技术用于观察湍流通量，并计算出特定位置的粗糙度值。获得的数据集用于驱动点消融模型，并评估文献中最常用的体方法和粗糙度长度方案。模拟烧蚀显示与季节，每日和次日时间尺度上的观测速率吻合良好，有效地关闭了表面能平衡，并在通量观测方法中具有很高的置信度。在整个季节中，净辐射是融化能量的主要贡献者（65.2％），其次是显热通量（29.7％），而在持续的大雨期间，降雨热通量是每日时间尺度上的重要贡献者（最高20％（第1天）。研究表面观察到的动量粗糙度长度（雪：10-3.8 m;冰：10-2.2 m）与以前的发现基本一致，而标量值（温度：10-4.6 m;水蒸气：10-6 m）与动量相比有显着差异，不同意粗糙度长度相等的假设。在测试的三种总体方法稳定性方案中，基于Monin-Obukhov长度的函数返回的平均日通量值最接近所观察到的值，但在次日时间尺度上表现不佳，并且出现了通量高估的时期。

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