Zonal asymmetry of Fwall

Overland and Turet (1994) compiled a vertical and latitudinal cross section of Fwall at 70° N for winter. This was done by plotting the summed fluxes of sensible heat, latent heat and potential energy at each pressure level and longitude (Figure 3.10). In accord with Figure 3.9, the poleward energy flux exhibits strong variation with height. There is also considerable zonal asymmetry at any pressure level. The most dominant pathway for energy transfer into the north polar cap is around the prime meridian. It is maximized between 800 hPa and 600 hPa, pointing to a control by transient eddies, associated with the primary North Atlantic cyclone track mentioned in Chapter 2 and explored more in the next chapter. However, Tsukernik et al. (2004) note that the longitude of this winter maximum corresponds roughly to the Norwegian Sea. This region is characterized by high convective heating rates associated with cold winter airmasses moving over open ocean waters. It appears that this regional heat source is an important contributor to the energy budget of the Arctic atmosphere.

There are two other relative maxima. The one centered around 100° W and between about 800 and 600 hPa points to a control by transient eddies. The other, centered approximately around the date line, shows the strongest fluxes at high levels indicative of control by the mean meridional circulation and standing eddies. However, fluxes in this sector are also large at lower levels, which according to Tsukernik et al. (2004) can be related to wintertime convective heating in the Bering Sea region.

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