Post World War II Trends in Tropical Pacific Surface Trades

D. E. Harrison NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington

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Abstract

Multidecadel time series of surface winds from central tropical Pacific islands are used to compute trends in the trade winds between the end of WWII and 1985. Over this period, averaged over the whole region, there is no statistically significant trend in speed or zonal or meridional wind (or pseudostress). However, there is some tendency, within a few degrees of the equator, toward weakening of the easterlies and increased meridional flow toward the equator. Anomalous conditions subsequent to the 1972–73 ENSO event make a considerable contribution to the long-term trends. The period 1974–80 has been noted previously to have been anomalous, and trends over that period are sharply greater than those over the longer records.

Abstract

Multidecadel time series of surface winds from central tropical Pacific islands are used to compute trends in the trade winds between the end of WWII and 1985. Over this period, averaged over the whole region, there is no statistically significant trend in speed or zonal or meridional wind (or pseudostress). However, there is some tendency, within a few degrees of the equator, toward weakening of the easterlies and increased meridional flow toward the equator. Anomalous conditions subsequent to the 1972–73 ENSO event make a considerable contribution to the long-term trends. The period 1974–80 has been noted previously to have been anomalous, and trends over that period are sharply greater than those over the longer records.

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