Observations of the stratospheric final warmings in the two hemispheres

Abstract

A comparison is made of the stratospheric final warmings which occurred in the two hemispheres. The dataset for this study consists of the NMC 1200 GMT analysis between 0.4 and 1000mb during 1982. The transformed Eulerian mean diagnosis is used for examining the wave, mean-flow interaction. The final warming occurred around March 31 in the Northern Hemisphere (NH) and around October 20 in the Southern Hemisphere (SH). Both warmings were associated with the enhanced planetary scale (wavenumber 1) wave activity. The final warming in the SH is more rapid and intense, which is consistent with the fact that the planetary scale wasve activity in the SH stratosphere is more intense than that in the NH stratosphere during the spring season. In the SH the polar easterly did not descend below 10mb after the final warming and circulation reversal below 10mb occurred about one month later, while the polar easterly kept descending to 50mb in the NH. The equatorial easterly in the lower stratosphere extended and connected to the polar easterly in the upper stratosphere of the SH, while the connection was not observed in the NH. A few days before the final warmings, the double jet structures were observed in the troposphere for both cases: The feature of the final warming in the SH of 1982 is very similar to that of 1979 studied by Yamazaki and Mechoso (1985).