Meridional Atmospheric Teleconnections Over The North Pacific From 1950 to 1972

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  • 1 Scripps Institution of Oceanography, University of California at San Diego, La Jolla, Cailf.
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Abstract

The meridional atmospheric teleconnections over the central North Pacific Ocean during winter are investigated by correlating the year-to-year fluctuations in the convective activity at the Equator, mid-latitude pressure/wind system, and subtropical pressure/wind system from 1950 to 1972. To establish fluctuations in these climatological systems, we consider the 23-yr time sequences of the maximum strength of the subtropical ridge, maximum intensity of the Aleutian Low, and strength of convective activity at the Equator, the latter inferred from the rainfall and sea-surface temperature at Canton Island (2°48′S, 171°43′W) observed by numerous authors to be representative of rainfall and sea-surface temperature over the entire central and eastern equatorial Pacific Ocean.

Upon cross correlation of these time sequences, we find that, throughout the two decades from 1950 to 1972, the intensity of the subtropical ridge and of the Aleutian Low were significantly correlated with one another (−0.50) as were the absolute magnitudes of their associated wind systems, the westerlies and northeast trades (0.83). Only during 1964–72, however, was the intensity of the Aleutian Low correlated (0.62) with fluctuations in the convective activity of the Equator. This indicates that the anomaly activity in the mid-latitude and subtropical pressure/wind systems and in the convective activity at the Equator were closely coupled during this time period. Conversely, during 1950–63, the lack of correlation between the convective activity at the Equator and the mid-latitude pressure/wind system suggests that the anomalies in these two systems were decoupled, at least in a linear way.

Bjerknes has found that fluctuations in the convective activity along the Equator in the Pacific were in association with the global tropical “southern oscillation” from 1955 to 1967. This suggests that, during the period of our study prior to 1964, the fluctuations in the mid-latitude pressure/wind system were independent of the fluctuations of sea-level pressure in the tropical latitudes of the world. However, the results of this paper together with the work of Bjerknes suggest that, after 1963, the mid-latitude pressure/wind system fluctuated in concert with the fluctuations of sea-level pressure over the tropical latitudes of the world. Speculation as to the causes for the approximate decadal variation in the meridional atmospheric teleconnections over the North Pacific is presented in terms of the decadal fluctuations found in the long-term trends of the major atmospheric systems.

Abstract

The meridional atmospheric teleconnections over the central North Pacific Ocean during winter are investigated by correlating the year-to-year fluctuations in the convective activity at the Equator, mid-latitude pressure/wind system, and subtropical pressure/wind system from 1950 to 1972. To establish fluctuations in these climatological systems, we consider the 23-yr time sequences of the maximum strength of the subtropical ridge, maximum intensity of the Aleutian Low, and strength of convective activity at the Equator, the latter inferred from the rainfall and sea-surface temperature at Canton Island (2°48′S, 171°43′W) observed by numerous authors to be representative of rainfall and sea-surface temperature over the entire central and eastern equatorial Pacific Ocean.

Upon cross correlation of these time sequences, we find that, throughout the two decades from 1950 to 1972, the intensity of the subtropical ridge and of the Aleutian Low were significantly correlated with one another (−0.50) as were the absolute magnitudes of their associated wind systems, the westerlies and northeast trades (0.83). Only during 1964–72, however, was the intensity of the Aleutian Low correlated (0.62) with fluctuations in the convective activity of the Equator. This indicates that the anomaly activity in the mid-latitude and subtropical pressure/wind systems and in the convective activity at the Equator were closely coupled during this time period. Conversely, during 1950–63, the lack of correlation between the convective activity at the Equator and the mid-latitude pressure/wind system suggests that the anomalies in these two systems were decoupled, at least in a linear way.

Bjerknes has found that fluctuations in the convective activity along the Equator in the Pacific were in association with the global tropical “southern oscillation” from 1955 to 1967. This suggests that, during the period of our study prior to 1964, the fluctuations in the mid-latitude pressure/wind system were independent of the fluctuations of sea-level pressure in the tropical latitudes of the world. However, the results of this paper together with the work of Bjerknes suggest that, after 1963, the mid-latitude pressure/wind system fluctuated in concert with the fluctuations of sea-level pressure over the tropical latitudes of the world. Speculation as to the causes for the approximate decadal variation in the meridional atmospheric teleconnections over the North Pacific is presented in terms of the decadal fluctuations found in the long-term trends of the major atmospheric systems.

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