Application of the Modified Ertel's Potential Vorticity to Investigation of Atmospheric Climate Variability

The arbitrariness existing in Ertel's general definition of potential vorticity (EPV) is used to arrive at an "optimal" modified PV in the sense of minimizing the material time-rate of change of PV due to diabatic heating and friction. The new modified PV and some functionals of it are found to be quasi-conservative in climatic processes. They can be used with some advantage for investigations of climate regimes.

Applying such functionals as vorticity charge, and informational entropy of air mass distribution on modified Ertel's potential vorticity to the study of the January and July circulation statistics temporal behaviour we detected a progressive growth of the equator-to-pole air surface temperature difference in the Southern Hemisphere during the 1980s. This trend is accompanied by a decrease of the meridional temperature gradient in January for the Northern Hemisphere. Attributing the latter to the overall warming in the Northern Hemisphere one might hypothesise that this meridional temperature gradient diminishing should result in reduction of the standing planetary waves generation over the Northern Hemisphere. This should lead to poorer wave-activity propagation into the Southern Hemisphere, then to weakening of the induced meridional heat fluxes there and, as a result, to temperature descend over the Antarctic polar region.