CLAES observations of CLONO 2 and HNO 3 in the Antarctic stratosphere, between June 15 and September 17, 1992

The Cryogenic Array Etalon Spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite (UARS) began viewing the stratosphere in October 1991. This paper presents preliminary retrievals of ClONO 2 and HNO 3 from the CLAES measurements for selected days in June, July, August, and September of 1992 for the southern hemisphere. The data shows that by July 10, lower stratospheric ClONO 2 and HNO 3 have developed high “collar” regions surrounding the polar vortex, and low values inside the vortex. This general structure is sustained through September 17, although the ClONO 2 values inside the vortex increase significantly by this date. The data suggests that substantial sequestration of gaseous HNO 3 in polar stratospheric clouds occurs in the early winter Antarctic stratosphere, accompanied by the conversion of ClONO 2 to reactive chlorine through heterogeneous processes on the PSCs.