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Teleconnections between Tropical Atlantic Sea Surface Temperatures and Midlatitude 50 kPa Heights during 1964–1986

M. DéquéCentre National de Recherches Météorologiques (DMN/EERM) Toulous, France

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J. ServainCentre National de Recherches Météorologiques (DMN/EERM) Toulous, France

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Abstract

Connections between departures from the seasonal cycle of sea surface temperature (SST) in the tropical Atlantic and 50 kPa height over the midlatitude North Atlantic are studied for the period 1964–86. The teleconnections in both time and space are studied using canonical correlation analyses performed on the observed fields filtered by their first empirical orthogonal functions. By shifting the atmospheric time series relative to the oceanic one, the method yields estimates of the best correlation patterns. Two modes of teleconnection emerge, and both involve the midlatitude atmosphere leading the tropical ocean. The first linkage, being almost in phase, seems to be controlled by a direct mechanism. The second one, with a two season time lag, involves the global ocean-atmosphere circulation and is weakly correlated with a Southern Oscillation index. Both phenomena have strong seasonality. Like the midlatitude oceans, therefore, the tropical Atlantic seems to be led by the atmosphere and there is no evidence, unlike the tropical Pacific, of surface temperature anomalies inducing a midlatitude atmospheric response.

Abstract

Connections between departures from the seasonal cycle of sea surface temperature (SST) in the tropical Atlantic and 50 kPa height over the midlatitude North Atlantic are studied for the period 1964–86. The teleconnections in both time and space are studied using canonical correlation analyses performed on the observed fields filtered by their first empirical orthogonal functions. By shifting the atmospheric time series relative to the oceanic one, the method yields estimates of the best correlation patterns. Two modes of teleconnection emerge, and both involve the midlatitude atmosphere leading the tropical ocean. The first linkage, being almost in phase, seems to be controlled by a direct mechanism. The second one, with a two season time lag, involves the global ocean-atmosphere circulation and is weakly correlated with a Southern Oscillation index. Both phenomena have strong seasonality. Like the midlatitude oceans, therefore, the tropical Atlantic seems to be led by the atmosphere and there is no evidence, unlike the tropical Pacific, of surface temperature anomalies inducing a midlatitude atmospheric response.

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