ENSO forced variations of the sea surface temperature and adjusted sea level along the west coast of the United States
Skillman, John B.
Schwing, Frank B.
Collins, Curtis A.
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Daily coastal surface temperature and adjusted sea level data for the period 1955-1988 were used to characterize the surface temperature and adjusted sea level anomalies, and the propagation of features along the west coast of the United States during El Nino-Southern Oscillation (ENSO). The strong ENSO years examined were 1957-58, 1972-73, and 1982-83. Moderate ENSO years used were 1966, 1976, and 1987. To look at regional differences in the signals, the time series of daily coastal surface temperature and adjusted sea level were divided into three distinct regions: the southern region (i.e., Southern California), the central upwelling region (i.e., Central California), and the northern region (i. e., Northern California, Oregon, and Washington). The anomaly series were compared with cross-spectral analysis. Phase speeds and wavenumbers were estimated from the difference in phase between La Jolla and the other stations as a function of frequency band. These were used to characterize the structure of waves associated with the propagation. of the positive surface temperature and adjusted sea level anomalies. These wave characteristics were found to be consistent with coastally trapped internal Kelvin waves, due to their phase speed, wavelength and non-dispersive nature. Phase speeds for frequencies corresponding to 4-20 day periods were 60-100 km/day, based on temperature and sea level. A regression of wavenumber against frequency gives phase speeds of about 65-85 km/day, that is consistent with Kelvin wave theory for typical west coast ocean structure and bathymetry. During ENSO episoddes, strong warm surface temperature anomalies were found to exist along the west coast and were supported by high adjusted sea level anomalies. The use of daily observations was advantageous over traditional monthly data for this analysis.
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