Stratospheric final warmings in the Southern Hemisphere and their energetics

Using 9 years (1985-1993) data, final stratospheric warmings in the Southern Hemisphere are studied. Interannual variations in the onset date and the temperatures are noted. In 1985 the stratosphere was colder by about 5 K and the wave activity was less. This year the final warming got delayed. In contrast in 1988 the final warming occurred earlier when compared with the mean picture and the wave activity was more. An examination of Eliassen-Palm fluxes showed the important role of planetary waves in the wave-mean flow interaction. In the energetics the most spectacular change is the reduction of zonal kinetic energy. Before the warming the energy exchanges were P-z --> P-e --> K-e --> K-z <-- P-z and after the warming they were P-z <-- P-e <-- K-e --> K-z <-- P-z. The dramatic reduction of zonal kinetic energy seems to be due to two effects: the reduction in K-e --> K-z conversion and the weakening of direct meridional circulation.