Variability of the upper tropical Pacific Ocean model

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Abstract
Variability in the tropical Pacific Ocean is investigated by using the result of a linear, reduced‐gravity transport numerical model with realistic basin geometry in spherical coordinates. Observed monthly wind stress for 1961–1984 from ships drives the model. Upper layer thickness data for 1965–1984 are analyzed after dividing it into 12‐month running mean data and residual data. The former represents interannual variability, and the latter represents higher‐frequency (mainly seasonal) variability. The standard deviation in the equatorial region is relatively small for both variabilities. The standard deviation for the interannual variability is larger in the central and western Pacific Ocean outside the equatorial region, while the variation for the higher‐frequency variability is considerably larger even in the eastern region. The large amplitude of the standard deviation about the higher‐frequency variability is largely confined to the northern hemisphere. The map of the temporal decorrelation scale shows that the temporal decorrelation scale defined as an e‐folding scale is 9–12 months about the interannual variability almost everywhere. The zonal decorrelation scale shows large changes in different regions and at different times, while the meridional decorrelation scale shows small changes. The zonal decorrelation scale decreases with increasing latitude. The zonal decorrelation scale about the interannual variability is much larger than that about the higher‐frequency variability. These data may be helpful for designing field observing programs using expendable bathythermographs and drifters.