Applicability of the Planar Fit Technique in Estimating Surface Fluxes over Flat Terrain using Eddy Covariance
Applicability of the Planar Fit Technique in Estimating Surface Fluxes over Flat Terrain using Eddy Covariance
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DOI：
10.2480/agrmet.64.3.5
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发表时间：
2008
影响因子：
1.3
通讯作者：
K. Ono;M. Mano;A. Miyata;Y. Inoue
中科院分区：
文献类型：
--
作者：
K. Ono;M. Mano;A. Miyata;Y. Inoue
平面拟合技术是一种坐标旋转方案，广泛用于基于塔的涡流协方差测量。针对平均流表面的几何形状检查了该技术的适用性。基于在稻田平坦地形上获得的 3 年涡度协方差数据集的分析表明，几乎所有风向的平均流线都向上，这可能是由于仪器的流动扭曲所致。将单个平面拟合到凹流表面会导致平均流线的偏移和倾斜角计算错误。因此，半小时平均垂直风速和流向动量通量在平面拟合坐标中表现出不一致的分布。相比之下，它们在改进的平面拟合技术（扇形平面拟合）下是一致的，其中平均流平面是在中心角为 30° 的每个风扇区确定的。当平均流表面不是用平面近似时，平面拟合技术不适用。在这种情况下，扇形平面拟合可以是普通平面拟合的实用替代方案。
The planar fit technique is a coordinate rotation scheme widely used for tower-based eddy covariance measurements. Applicability of this technique was examined with respect to the geometry of the mean stream surface. Analyses based on a 3-year eddy-covariance dataset obtained over flat terrain of a paddy field revealed that the mean streamline was upward at almost all wind directions possibly because of flow distortion by the instruments. Fitting a single plane to the concave stream surface led to miscalculations in the offset and tilt angle of the mean streamline. Consequently, the half-hourly mean vertical wind velocity and streamwise momentum flux demonstrated inconsistent distributions in planar fit coordinates. In contrast, they were consistent under a modified planar fit technique, the sectorial planar fit, in which the mean stream plane was determined at each wind sector with a center angle of 30°. The planar fit technique is not applicable when the mean stream surface is not approximated by a plane. In such cases, the sectorial planar fit can be a practical alternative to the ordinary planar fit.