Persistence of the 500 mb Height Field during Northern Hemisphere Winter

John D. Horel Climate Research Group, Scripps Institution of Oceanography, La Jolla, CA 92093

Search for other papers by John D. Horel in
Current site
Google Scholar
PubMed
Close
Full access

Abstract

The persistence of the planetary-scale circulation during the Northern Hemisphere winters from 1965/66 to 1981/82 is documented. National Meteorological Center analyses of 500 mb geopotential height for the Northern Hemisphere poleward of 20°N are used. Instead of constructing auto-correlation maps based on lime series at grid points, time series are constructed that show the pattern correlations between daily hemispheric maps. These time series provide information on the day-to-day changes in persistence of the winter circulation and allow comparisons of the intraseasonal and interannual variability of persistence.

The hemispheric circulation is usually quite persistent from day-to-day; correlations between successive maps usually fall within the range 0.7 to 0.9. As the time between the maps is increased the correlations between these maps decreases at a rate faster than that expected of an autoregressive (red-noise) process. The hemispheric circulation rarely resembles closely the circulation a few days before unless synoptic scale waves are removed.

Subjectively defined criteria are used to identify quasi-stationary regimes i.e. periods during which the planetary-scale circulation is more persistant than usual. A total of 58 regimes encompassing 25% of the 2040 days am identified. Multiple regimes are evident during several winter. The quasi-stationary regimes exhibit considerable diversity in their spatial configurations. Comparison of the regimes using principal component analysis suggests that the most frequently reoccurring regime consists of a superposition of a wavenumber 3 pattern at roughly 50°N upon zonally symmetric components at middle and polar latitudes of opposing signs. However, this principal component explains only 17% 6f the variance contained in the 58 regimes.

Abstract

The persistence of the planetary-scale circulation during the Northern Hemisphere winters from 1965/66 to 1981/82 is documented. National Meteorological Center analyses of 500 mb geopotential height for the Northern Hemisphere poleward of 20°N are used. Instead of constructing auto-correlation maps based on lime series at grid points, time series are constructed that show the pattern correlations between daily hemispheric maps. These time series provide information on the day-to-day changes in persistence of the winter circulation and allow comparisons of the intraseasonal and interannual variability of persistence.

The hemispheric circulation is usually quite persistent from day-to-day; correlations between successive maps usually fall within the range 0.7 to 0.9. As the time between the maps is increased the correlations between these maps decreases at a rate faster than that expected of an autoregressive (red-noise) process. The hemispheric circulation rarely resembles closely the circulation a few days before unless synoptic scale waves are removed.

Subjectively defined criteria are used to identify quasi-stationary regimes i.e. periods during which the planetary-scale circulation is more persistant than usual. A total of 58 regimes encompassing 25% of the 2040 days am identified. Multiple regimes are evident during several winter. The quasi-stationary regimes exhibit considerable diversity in their spatial configurations. Comparison of the regimes using principal component analysis suggests that the most frequently reoccurring regime consists of a superposition of a wavenumber 3 pattern at roughly 50°N upon zonally symmetric components at middle and polar latitudes of opposing signs. However, this principal component explains only 17% 6f the variance contained in the 58 regimes.

Save