Characterizing energy balance closure over a heterogeneous ecosystem using multi-tower eddy covariance
Characterizing energy balance closure over a heterogeneous ecosystem using multi-tower eddy covariance
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DOI：
10.3389/feart.2023.1251138
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发表时间：
2024-01
影响因子：
2.9
通讯作者：
Brian J. Butterworth;Ankur R. Desai;D. Durden;H. Kadum;Danielle LaLuzerne;M. Mauder;Stefan Metzger;S. Paleri;Luise Wanner
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文献类型：
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作者：
Brian J. Butterworth;Ankur R. Desai;D. Durden;H. Kadum;Danielle LaLuzerne;M. Mauder;Stefan Metzger;S. Paleri;Luise Wanner
单点涡度相关测量地球表面能量收支经常发现可用能量和湍流热通量之间的不平衡。虽然这种不平衡缺乏一个明确的解释，但它仍然是一个持续的发现，从单点测量;一个与大气和生态系统模型的影响。这导致了一个推动密集的现场活动与时间和空间分布的传感器，以帮助确定能源平衡不关闭的原因。在这里，我们介绍了由高密度广泛阵列探测器2019（CHEESEHEAD 19）实现的Chequamegon异质生态系统能量平衡研究的结果-这是一项旨在研究地球表面能量预算如何响应北方威斯康星州森林生态系统表面空间异质性尺度的观测实验。该活动于2019年6月至10月进行，使用20个塔和一架低空飞行的飞机测量涡动协方差（EC）表面能量通量。在整个域中，能量平衡残差被发现是最高的下午，与表面不均匀性驱动的中尺度运动的时期相吻合。不同地点的残留量因每个地点的植被特征而异。植被高度和高度变率都与残差震级呈正相关。在从潜热主导的夏季到感热主导的秋季的季节转换过程中，能量平衡残差的大小稳步下降，但能量平衡比保持恒定在0.8。这是由于能量平衡方程的不同组成部分按比例移动，这表明两个季节不关闭的共同原因。此外，我们还测试了使用空间EC测量能量平衡的有效性。空间EC，其中的协方差计算的基础上，从空间均值的偏差，已被提出作为一种潜在的方式，以减少能量平衡残差纳入贡献比单站点，时间EC中尺度运动。在这里，我们用CHEESEHEAD 19数据集测试了空间EC的几种变化，但发现能量平衡闭合几乎没有改善，我们将其部分归因于空间EC具有挑战性的测量要求。
Single point eddy covariance measurements of the Earth’s surface energy budget frequently identify an imbalance between available energy and turbulent heat fluxes. While this imbalance lacks a definitive explanation, it is nevertheless a persistent finding from single-site measurements; one with implications for atmospheric and ecosystem models. This has led to a push for intensive field campaigns with temporally and spatially distributed sensors to help identify the causes of energy balance non-closure. Here we present results from the Chequamegon Heterogeneous Ecosystem Energy-balance Study Enabled by a High-density Extensive Array of Detectors 2019 (CHEESEHEAD19)—an observational experiment designed to investigate how the Earth’s surface energy budget responds to scales of surface spatial heterogeneity over a forest ecosystem in northern Wisconsin. The campaign was conducted from June–October 2019, measuring eddy covariance (EC) surface energy fluxes using an array of 20 towers and a low-flying aircraft. Across the domain, energy balance residuals were found to be highest during the afternoon, coinciding with the period of surface heterogeneity-driven mesoscale motions. The magnitude of the residual varied across different sites in relation to the vegetation characteristics of each site. Both vegetation height and height variability showed positive relationships with the residual magnitude. During the seasonal transition from latent heat-dominated summer to sensible heat-dominated fall the magnitude of the energy balance residual steadily decreased, but the energy balance ratio remained constant at 0.8. This was due to the different components of the energy balance equation shifting proportionally, suggesting a common cause of non-closure across the two seasons. Additionally, we tested the effectiveness of measuring energy balance using spatial EC. Spatial EC, whereby the covariance is calculated based on deviations from spatial means, has been proposed as a potential way to reduce energy balance residuals by incorporating contributions from mesoscale motions better than single-site, temporal EC. Here we tested several variations of spatial EC with the CHEESEHEAD19 dataset but found little to no improvement to energy balance closure, which we attribute in part to the challenging measurement requirements of spatial EC.