Analysis of SST Anomalies in the North Pacific and their Relation to 500mb Height Anomalies Over the Northern Hemisphere During 1969-1979

Abstract

Characteristics of the SST anomaly field in the North Pacific and their relationship with the 500mb geopotential height fluctuation in the Northern Hemisphere, were investigated, by using the 5°×5°grid SST data set for the North Pacific. This data set was newly calculated from the SST data file provided by the Japan Oceanographic Data Center. The typical zonal and meridional scales of the SST anomaly pattern are several and one to two thousands km, respectively. Typical SST anomaly patterns can be traced for several months to a year. Fluctuations with periods of several years are also found in spectral analyses for the SST anomaly field. The SST anomaly tends to appear almost simultaneously over a large area. Clear regularity is not found in the speed and the direction of the migration and/or the expansion of the SST anomaly pattern. However, for restricted periods, the SST anomaly pattern seems to move by advection.
In an EOF analysis of the SST anomaly, the first EOF shows an elliptic monopole spatial pattern centered on the central North Pacific. The time series of the coefficient of the first EOF shows a variation with periods of several months and of two to three years, but has no peak corresponding to the 1972/73 El Nino event. Our results of the EOF analysis are similar to those of Davis (1976), but somewhat different from Weare et al. (1976) and Kawamura (1984) because of differences in the domain of the analyses.
The SST fluctuations are highly correlated with 500mb height variations in the Northern Hemisphere. We could conclude based on the lag correlation analysis that the SST anomalies represented by the first EOF are caused by the 500mb height fluctuation corresponding to the PNA pattern.