Associations between West Pacific equatorial zonal winds and East Pacific SST anomalies
Date
1990-05
Authors
Collimore, Christopher C., author
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Abstract
Temporal relationships between atmospheric circulations in the equatorial West Pacific and sea surface temperature anomalies (SSTAs) in the East Pacific are examined for all phases of the El Nino-Southern Oscillation cycle. Strong correlations between time series of low-level zonal wind anomalies in the equatorial West Pacific and SSTAs over a broad area of the equatorial Ea.st Pacific are shown to exist during all phases of the interannual SST cycle, including El Ninos, La Ninas, and periods of near normal temperatures. Fluctuations of low-level zonal wind anomalies precede changes in SSTAs, suggesting a simple cause and effect relationship. A similar but weaker relationship exists between East Pacific SSTAs and anomalous tropical cyclone activity in the West Pacific, as measured by tropical cyclone days. Weaker correlations with low-level winds and tropical cyclone activity exist for SST anomalies from a smaller area in the extreme eastern Pacific. West Pacific low-level winds and tropical cyclone activity are also compared to the Southern Oscillation. An interpretation of all these associations is presented. It is suggested that long term fluctuations of low-level zonal winds in the equatorial West Pacific directly modulate SSTs in the equatorial Ea.st Pacific through the ocean Kelvin waves they excite while the ocean Rossby waves they excite are negligible in comparison (the wind of the stress associated with the low-level zonal winds may drive anomalous equatorial zonal ocean currents which also directly influence SSTs). Finally, it is speculated that the combined influences of several phenomena not directly associated with El Nino-Southern Oscillation circulations in the Pacific are the primary modulators of the interannual low-level wind fluctuations. In other words, it is suggested that the interannual fluctuations of low-level winds in the equatorial West Pacific are not necessarily part of feedback loops within the Pacific basin alone.
Description
May 1990.
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Subject
Ocean temperature -- Pacific Ocean
Ocean circulation
Ocean-atmosphere interaction