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- Author or Editor: Yukihiro Mori x
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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.
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.
Abstract
Spectra of the surface wind at Marcus Island (24°N, 154°E) in the subtropical Pacific area wore constructed over a wide frequency range from 10−1 to 5 × 10−5 Hz (periods from 6 h to about three years). The major kinetic energy peak is found at a period of about 6 days. Besides this peak, for the lower frequency range the significant peak is found at a period of 14–22 days. The latter peak is not found in the spectra at other places in the middle latitudes reported before and is significant in the warm season. This means that equatorial planetary-scale waves exert influence on the surface wind at this island. The diurnal and semidiurnal peaks are small but clearly found. The daily variation of the surface wind may be due to the diurnal and semidiurnal tidal waves of atmospheric pressure. Small peaks are found in some cases at or near the inertial period. Rotary spectra are calculated and also shown.
Abstract
Spectra of the surface wind at Marcus Island (24°N, 154°E) in the subtropical Pacific area wore constructed over a wide frequency range from 10−1 to 5 × 10−5 Hz (periods from 6 h to about three years). The major kinetic energy peak is found at a period of about 6 days. Besides this peak, for the lower frequency range the significant peak is found at a period of 14–22 days. The latter peak is not found in the spectra at other places in the middle latitudes reported before and is significant in the warm season. This means that equatorial planetary-scale waves exert influence on the surface wind at this island. The diurnal and semidiurnal peaks are small but clearly found. The daily variation of the surface wind may be due to the diurnal and semidiurnal tidal waves of atmospheric pressure. Small peaks are found in some cases at or near the inertial period. Rotary spectra are calculated and also shown.
