Spectrum of Long-Period Fluctuations of Surface Wind at Marcus Island

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.