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Persistence of Flow Patterns over North America and Adjacent Ocean Sectors

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  • 1 Scripps Institution of Oceanography, La Jolla, CA 92093
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Abstract

This paper constitutes an attempt to elucidate and account for the characteristics of persistence of mouth-to-month, season-to-season, and year-to-year midtropospheric flow patterns-patterns that control much of the weather and climate of North America.

The well-known signature of atmospheric forcing produced by normal seasonal factors is sharpened with new data, exposing a large residual of interannual variation to be documented and explained. In order to do this, several avenues are explored, including the preparation of statistics of pattern correlations stratified by month, season, year, and combinations thereof, as well as the stratification of data by quartiles representing high, low and intermediate persistence. Analyses of these data imply that certain flow patterns are more stable than others, and that the more stable patterns have stronger anomalies, are associated with mutually reinforcing teleconnections, and tend to be well reflected in persistent zonal wind speed profiles. Strong month-to-month persistence in the cold season accompanies or often precedes by a full year the mature stage of El Niño, thereby suggesting that a sustained anomalies atmospheric flow pattern helps instigate large tropical SST warmings.

Abstract

This paper constitutes an attempt to elucidate and account for the characteristics of persistence of mouth-to-month, season-to-season, and year-to-year midtropospheric flow patterns-patterns that control much of the weather and climate of North America.

The well-known signature of atmospheric forcing produced by normal seasonal factors is sharpened with new data, exposing a large residual of interannual variation to be documented and explained. In order to do this, several avenues are explored, including the preparation of statistics of pattern correlations stratified by month, season, year, and combinations thereof, as well as the stratification of data by quartiles representing high, low and intermediate persistence. Analyses of these data imply that certain flow patterns are more stable than others, and that the more stable patterns have stronger anomalies, are associated with mutually reinforcing teleconnections, and tend to be well reflected in persistent zonal wind speed profiles. Strong month-to-month persistence in the cold season accompanies or often precedes by a full year the mature stage of El Niño, thereby suggesting that a sustained anomalies atmospheric flow pattern helps instigate large tropical SST warmings.

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