Some Long-Term Relations Between Equatorial Sea-Surface Temperature, the Four Centers of Action and 700 mb Flow

Abstract

The relation between sea-surface temperature (SST) in the eastern equatorial Pacific (0°?10°S, 180°?;80°W), and surface pressure, latitude and longitude of the four centers of action (Icelandic and Aleutian Lows, Atlantic and Pacific Highs), has been examined based on seasonal data from 1899 through 1978. The relation between this SST and indexes of the 700 mb zonal flow has been examined based on seasonal data from 1949 through 1983. Warm equatorial SST has been associated, in a significant fashion, with stronger than average westerly winds at 700 mb in the 20?35°N latitude band, weaker than average westerly winds at 700 mb in the 35?55°N band, below-average central pressure of the Pacific High, Atlantic High and Aleutian Low, southward displacement of the Icelandic Low, and eastward displacement of the Atlantic High. The only evidence of a precursor to warm equatorial SST (El Niño) is the relatively small distance between the centers of the Aleutian Low and Pacific High two seasons before warmest SST, but this relation, though indicated to be significant, is too weak to be of use in prediction.