Meridional Eddy Sensible Heat Fluxes in the Extremes of the Pacific/North American Teleconnection Pattern

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  • 1 Department of Geography, The Ohio State University, Columbus, Ohio
  • | 2 Department of Geography, University of California-Los Angeles, Los Angeles, California
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Abstract

The geographical distribution of meridional eddy sensible heat transport in the extremes of the Pacific/North American (PNA) teleconnection pattern is examined and compared to heat transport occurring in conjunction with other regional teleconnections. The heat fluxes are estimated using 700-mb air temperatures and geostrophic winds during 12 winter months when the PNA index reaches its highest values (large-amplitude standing ridge and trough pattern over North America) and during 12 months when it is lowest (relatively zonal flow across the continent). The standing wave fluxes are generally largest in the positive PNA phase, especially across latitudes 45°–55°N, although the flux between 60°–75°N is not as great as in the negative phase, when poleward heat transport is strong over northern Canada and near Iceland. The largest spatial heat flux variations in the extremes of the PNA occur in areas with long-term climatological flux maxima and relatively large long-term standard deviations. These include eastern Asia, the northeastern Pacific, western North America, and over the Atlantic Ocean, although in the latter region the maxima are split between Newfoundland during positive PNA index months and Iceland in negative PNA index months. In the extremes of the PNA, there is a strong tendency for the relative magnitudes of the standing and transient eddy fluxes to be out of phase in many areas of the hemisphere. This characteristic is not predominant in other regional teleconnections although it occurs in the western Pacific pattern. In other teleconnections the eddy fluxes are generally in phase, contributing directly to the total eddy flux, and centers of flux maxima do not generally correspond to those appearing in the long-term means.

Abstract

The geographical distribution of meridional eddy sensible heat transport in the extremes of the Pacific/North American (PNA) teleconnection pattern is examined and compared to heat transport occurring in conjunction with other regional teleconnections. The heat fluxes are estimated using 700-mb air temperatures and geostrophic winds during 12 winter months when the PNA index reaches its highest values (large-amplitude standing ridge and trough pattern over North America) and during 12 months when it is lowest (relatively zonal flow across the continent). The standing wave fluxes are generally largest in the positive PNA phase, especially across latitudes 45°–55°N, although the flux between 60°–75°N is not as great as in the negative phase, when poleward heat transport is strong over northern Canada and near Iceland. The largest spatial heat flux variations in the extremes of the PNA occur in areas with long-term climatological flux maxima and relatively large long-term standard deviations. These include eastern Asia, the northeastern Pacific, western North America, and over the Atlantic Ocean, although in the latter region the maxima are split between Newfoundland during positive PNA index months and Iceland in negative PNA index months. In the extremes of the PNA, there is a strong tendency for the relative magnitudes of the standing and transient eddy fluxes to be out of phase in many areas of the hemisphere. This characteristic is not predominant in other regional teleconnections although it occurs in the western Pacific pattern. In other teleconnections the eddy fluxes are generally in phase, contributing directly to the total eddy flux, and centers of flux maxima do not generally correspond to those appearing in the long-term means.

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