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首页> 外文会议>Autonomous Air and Ground Sensing Systems for Agricultural Optimization and Phenotyping Conference >To What Extend Does the Eddy Covariance Footprint Cutoff Influence the Estimation of Surface Energy Fluxes Using Two Source Energy Balance Model and High-Resolution Imagery in Commercial Vineyards?
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To What Extend Does the Eddy Covariance Footprint Cutoff Influence the Estimation of Surface Energy Fluxes Using Two Source Energy Balance Model and High-Resolution Imagery in Commercial Vineyards?

机译：在商业葡萄园中，使用两源能量平衡模型和高分辨率图像，涡流协方差足迹截止会影响表面能通量的估算吗？

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Validation of surface energy fluxes from remote sensing sources is performed using instantaneous field measurements obtained from eddy covariance (EC) instrumentation. An eddy covariance measurement is characterized by a footprint function / weighted area function that describes the mathematical relationship between the spatial distribution of surface flux sources and their corresponding magnitude. The orientation and size of each flux footprint / source area depends on the micro-meteorological conditions at the site as measured by the EC towers, including turbulence fluxes, friction velocity (U_(star)), and wind speed, all of which influence the dimensions and orientation of the footprint. The total statistical weight of the footprint is equal to unity. However, due to the large size of the source area / footprint, a statistical weight cutoff of less than one is considered, ranging between 0.85 and 0.95, to ensure that the footprint model is located inside the study area. This results in a degree of uncertainty when comparing the modeled fluxes from remote sensing energy models (i.e., TSEB2T) against the EC field measurements. In this research effort, the sensitivity of instantaneous and daily surface energy flux estimates to footprint weight cutoffs are evaluated using energy balance fluxes estimated with multispectral imagery acquired by AggieAir sUAS (small Unmanned Aerial Vehicle) over commercial vineyards near Lodi, California, as part of the ARS-USDA Agricultural Research Service's Grape Remote Sensing Atmospheric Profile and Evapotranspiration experiment (GRAPEX) project. The instantaneous fluxes from the eddy covariance tower will be compared against instantaneous fluxes obtained from different TSEB2T aggregated footprint weights (cutoffs). The results indicate that the size, shape, and weight of pixels inside the footprint source area are strongly influenced by the cutoff values. Small cutoff values, such as 0.3 and 0.3S, yielded high weights for pixels located within the footprint domain, while large cutoffs, such as 0.9 and 0.95, result in low weights. The results also indicate that the distribution of modelled LE values within the footprint source area are influenced by the cutoff values. A wide variation in LE was observed at high cutoffs, such as 0.90 and 0.95, while a low variation was observed at small cutoff values, such as 0.3. This happens due to the large number of pixel units involved inside the footprint domain when using high cutoff values, whereas a limited number of pixels are obtained at lower cutoff values.
机译：使用从涡动协方差（EC）仪器获得的瞬时场测量值对来自遥感源的表面能通量进行验证。涡动协方差测量的特征是足迹函数/加权面积函数，该函数描述了表面通量源的空间分布及其相应大小之间的数学关系。每个通量足迹/源区域的方向和大小取决于EC塔测量的现场微气象条件，包括湍流，摩擦速度（U_（star））和风速，所有这些都会影响通气量。足迹的尺寸和方向。足迹的总统计权重等于1。但是，由于源区域/足迹的大小很大，因此考虑将统计权重截断值小于1，范围在0.85至0.95之间，以确保足迹模型位于研究区域内。当将来自遥感能量模型（即TSEB2T）的建模通量与EC场测量值进行比较时，这会导致一定程度的不确定性。在这项研究工作中，使用AggieAir sUAS（小型无人飞行器）在加利福尼亚州洛迪附近的商业葡萄园获得的多光谱图像估算的能量平衡通量，评估了瞬时和每日表面能通量估计值对足迹权重的敏感性，这是该计划的一部分ARS-USDA农业研究局的葡萄遥感大气廓线和蒸散实验（GRAPEX）项目。来自涡流协方差塔的瞬时通量将与从不同TSEB2T集合足迹权重（临界值）获得的瞬时通量进行比较。结果表明，足迹源区域内像素的大小，形状和权重受截止值的强烈影响。较小的截止值（例如0.3和0.3S）会为占位区域内的像素产生较高的权重，而较大的截止值（例如0.9和0.95）会导致较低的权重。结果还表明，建模LE值在足迹源区域内的分布受截止值的影响。在高截止值（例如0.90和0.95）下观察到LE的宽幅变化，而在小截止值（例如0.3）下观察到LE的低变化。发生这种情况是由于在使用高截止值时占用的覆盖区域内有大量像素单元，而在较低的截止值下获得的像素数量有限。

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