Vol.29 No.4(8) [2007]

Evaluating the Variability of Sea-surface Wind Stress by the Combined Use of Eddy Correlation and Inertial Dissipation Methods

Koji SAKURAGI, Yuji SUGIHARA, Takuya ANDO, Shigeatsu SERIZAWA and Hiroshi YOSHIOKA


Field measurements of wind stress over the ocean surface were made at a sea observation tower by the combined use of the eddy correlation and inertial dissipation methods, which are referred to as “ECM” and “IDM” hereafter, respectively. The values of the wind stresses obtained from both methods should agree well under ideal surface layer conditions. Thus, confirming the degrees of agreement between the stresses from ECM and IDM make it possible to reveal how air-sea momentum transfer varies depending on wave-field conditions. The present data show the degrees of agreement to depend significantly on the wave age in the case of pure windsea. This means that imbalance factors in the turbulent kinetic energy equation become large with increasing the wave age. Also, the degrees of agreement between ECM and IDM are found to vary with the deflection of the wind stress vector from the wind direction, which are caused by the presence of swell.