Transequatorial Effects of Sea-Surface Temperature Anomalies in a Global General Circulation Model

Abstract

The global response of the atmosphere, as simulated by the Mintz-Arakawa, two-level, general circulation model, to a persistent anomalous pool of warm sea-surface temperatures (SST) in the extratropical Pacific Ocean is examined in this descriptive study in terms of the meridional pole-to-pole profile of the zonally averaged 600-mb surface for periods up to 90 days. Following an initial hydrostatic inflation of the isobaric surface in the latitude of the warm pool, effects spread poleward within the hemisphere, then begin to appear after about 2?3 weeks in high latitudes of the opposite hemisphere, but with little or no response in the Tropics. The same sea temperature anomaly field generates a stronger response in winter than in summer and a very different reaction when located in the Southern Hemisphere than when in the Northern Hemisphere. After a month of thermal forcing, the response to an SST anomaly is at least as large in the opposite hemisphere as in the hemisphere of the anomaly. A winter hemisphere responds more rapidly to an SST anomaly in the opposite hemisphere than does a summer hemisphere. Vacillation between low and high meridional wave number patterns is observed in the computed reaction to the warm pool.