Some relationships between sea level and wind in the equatorial Pacific

Abstract

The trade wind in the Equatorial Pacific region is subject to regular four-day fluctuations associated with the westward passage of planetary-type, atmospheric waves. This wind fluctuation causes the sea surface to rise and fall with the same frequency. At times, these surface waves attain a double amplitude of ten centimeters and stand out prominently against the background noise. Statistical analysis shows these waves to be coherent over great distancias from the Line IsIands to the Phoenix, and from the latter to the Gilbert Islands, a total distancia of 3,000 Km. The background activity, in the same frequency range, is not this coherent. The phase relations at various sea-level observatories set up during the International Geophysical Year are consistent with a westward travelling progressive wave, as one might expect would be forced by the wave in the trade wind. In the Phoenix Islands, where the four-day activity is greatest there are significant, well-resolved spectral peaks at periods of five days and 2.7 days, in addition to the more prominent four day peak. These peaks are remarkably narrow, being almost indistinguishable from true lines. The origin of these peaks has not been explained.