Specification of Sea Surface Temperature Anomaly Patterns in the Eastern North Pacific

Abstract

Observed changes in sea surface temperature anomaly patterns on monthly and seasonal time scales are related to anomalous circulation patterns in the overlying atmosphere using data collected from the eastern North Pacific over a 10-year period (1961–70). Three monthly (November 1969, December 1969, January 1970) and four seasonal (fall 1969, winter 1969–70, spring 1970, summer 1970) case studies are described which show that the observed anomalous temperature changes can be explained quite well by relating them to anomalous heat transfer across the air-sea interface and heat advection by anomalous wind-driven ocean surface currents. These interactions are documented by charts showing the anomaly patterns of sea surface temperature change, sea level pressure, types of heat transfer across the air-sea interface, and wind drift currents. In addition, correlations computed between the anomaly patterns for each of the periods studied show that the interactions hypothesized have statistical significance. Although only seven case studies are described, the results are representative of those for most of the other months and seasons in the 10-year period. An analysis of several years of data from Station PAPA (50N,145W), which included observed mixed layer depth values, indicates that between-year fluctuations in mixed layer depths can have a large effect in determining anomalous sea surface temperature changes, particularly when new seasonal thermoclines are forming. These effects should he included in any method used to specify (or predict) anomaly changes in order to avoid the relatively large errors that can occur from using long-term mean values.