Application of the band-pass covariance technique to portable flux measurements over the Tibetan Plateau
Application of the band-pass covariance technique to portable flux measurements over the Tibetan Plateau
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DOI：
10.1029/2005wr003954
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发表时间：
2005-09-10
影响因子：
5.4
通讯作者：
Wang, JM
中科院分区：
文献类型：
--
作者：
Asanuma, J;Ishikawa, H;Wang, JM
利用简单便携的湍流观测系统，对青藏高原稀疏草原地区白天采集的湍流资料进行了两种带通协方差分析。温度和特定湿度之间的相干谱（其是相关系数的谱对应物）被用作含能范围的动态指标以及在较高频率下的传感器衰减的动态指标。通过与涡动协方差法的独立测量值的比较表明，带通协方差法的原始版本偶尔会失败。这表明温度和水汽之间的相似性被打破，特别是在最低频率区域。另一方面，与涡度相关方法计算的潜热通量与先进的版本表现出足够的协议。本文表明，目前实施的高级版本与嵌入式自校准程序提供了一个强大的方法，频率外推标量通量测量不稳定的条件下。
Two versions of the band- pass covariance technique were applied to the turbulence data collected during daytime with a simple and portable measurement system over the sparse grasslands of the Tibetan Plateau. The coherency spectra between the temperature and the specific humidity, which is a spectral counterpart of the correlation coefficient, were used as a dynamic indicator of the energy- containing ranges as well as that of the sensor attenuation at higher frequencies. The comparison with independent measurements by the eddy covariance method showed that the original version of the band- pass covariance technique occasionally fails. This indicates breakdowns of the similarity between the temperature and the water vapor, especially in the lowest- frequency regions. On the other hand, the latent heat flux computed with the advanced version exhibited adequate agreement with the eddy covariance method. This paper demonstrates that the current implementation of the advanced version with the embedded self-calibration procedure provides a robust method of frequency extrapolation in scalar flux measurements under unstable conditions.