Semidiurnal Tidal Wind Oscillation at Marcus Island

Abstract

The daily variation of the surface wind at Marcus Island (24°N, 154°E) in the subtropical Pacific area has been investigated with respect to the semidiurnal atmospheric tide. The semidiurnal oscillations of scalar wind speed and vector components of wind have been analyzed harmonically. The phase of the zonal wind component in local time agrees with the observed values at Bermuda and in the Atlantic trades. Using the Ekman model the semidiurnal tidal wind oscillation in the planetary boundary layer has been investigated, and an analytic solution has been obtained. In order to fit the theoretical tidal wind oscillation to the observed one, the eddy viscosity K should be smaller than 0.1 m2 s?1. This value of K appears smaller than the representative value in the trades. This suggests the limitation of the simple model.