Cutoff Time Scale of Eddy Covariance Method for Measuring Air-Sea Momentum Flux

Authors

  • Hao Jiang, Zhen-Tao Yu, Bao-Qiang Zhang, Zhong-Kuo Zhao, Jin-Bao Song

Abstract

For the purpose of directly measurement of air turbulence in Marine Atmospheric Boundary Layer, Cutoff Time Scale (CTS) is required at ?rst for the so-called Eddy Covariance Method. However, traditional setting is a constant which presents a dilemma. Here, we suggest a new data-oriented CTS scheme, for objectively selecting CTS and thus computing the turbulence momentum ?ux. We used two in-situ datasets, whereas the ?rst is the buoy-based Yellow Sea observation, and the second is the tower-based South China Sea observation. We determined CTS by the frequency gap between turbulence and relatively low frequency component, and the frequency separation is achieved by both Multi-Resolution Decomposition (MRD) and Empirical Mode Decomposition (EMD). On the one hand, CTSs from MRD and EMD are less than common constantly setting (10 minutes). On the other hand, we evident the dependence of CTS on the root-mean-squared energy (RMSE) of wind speed, which lead to a new parameterization scheme. For application, new scheme releases better estimation of air-sea momentum ?ux than those by traditional constantly setting.

Published

2020-02-29

Issue

Section

Articles