STRATOSPHERIC WARMINGS DURING FEBRUARY AND MARCH 1993

Two stratospheric warmings during February and March 1993 are describe d using UKMO analyses, calculated PV and diabatic heating, and N2O obs erved by the CLAES instrument on the UARS. The first warming affected temperatures over a larger region, while the second produced a larger region of reversed zonal winds. Tilted baroclinic zones formed in the temperature field, and the polar vortex tilted westward with height. N arrow tongues of high PV and low N2O were drawn off the polar vortex, and irreversibly mixed. Tongues of material were drawn from low latitu des into the region between the polar vortex and the anticyclone; diab atic descent was also strongest in this region. Increased N2O over a b road region near the edge of the polar vortex indicates the importance of horizontal transport. N2O decreased in the vortex, consistent with enhanced diabatic descent during the warmings.