SPATIAL AND TEMPORAL VARIABILITY OF CLONO2, HNO3, AND O-3 IN THE ARCTIC WINTER OF 1992 1993 AS OBTAINED BY AIRBORNE INFRARED-EMISSION SPECTROSCOPY/

In the winter of 1992/1993 the airborne Michelson interferometer for p assive atmospheric sounding (MIPAS-FT) was operated on board a German research aircraft (Transall C-160) to record infrared emission spectra of the atmosphere inside and outside the Arctic vortex. Measurements were made during four campaigns between December 4, 1992, and March 29 , 1993, in the European Arctic as well as over central and southern Eu rope (82 degrees N - 37.5 degrees N). We present the retrieved zenith column amounts of the stratospheric trace gases ClONO2, HNO3, and O-3 of this period. Inside the polar vortex, the column amounts of ClONO2 and HNO3 were considerably enhanced already in early December, up to 3 .1 x 10(15) cm(-2) and 2.7 x 10(16) cm(-2), respectively. Around the e nd of January, low ClONO2 (1 x 10(15) cm(-2)) and high HNO3 column amo unts (up to 3.7 x 10(16) cm(-2)) were observed inside the vortex; wher eas a highly variable ''collar'' of ClONO2 had developed at the vortex edge. During March, after temperatures had been above the threshold f or polar stratospheric clouds (PSCs) for several weeks, we measured lo wer HNO3 (below 2.5 x 10(16) cm(-2)) and very high ClONO2 column amoun ts (up to 6 x 10(15) cm(-2)) inside the vortex. Thus a major part of t he reactive chlorine had been converted into ClONO2, and the potential for rapid ozone depletion was reduced markedly in the region observed . On March 10, when the polar vortex extended southward to the Mediter ranean, ClONO2 column amounts as high as 4.6 x 10(15) cm(-2) were obse rved at 40 degrees N. At the end of March, considerable amounts of ClO NO2 (up to 3.4 x 10(15) cm(-2)) were measured also far outside the vor tex.