Using several remote sensing techniques on board a research aircraft (Transall C‐160), we measured the stratospheric column amounts of O 3 , NO 2 , OClO, ClNO 3 , and HNO 3 , and the height‐resolved aerosol backscattering ratios during March 7–10, 1993. During this period the polar vortex extended from the Arctic well into the Mediterranean (35°N). Several underflights of the vortex and its edge region were conducted, covering Arctic (79°N) to Mediterranean latitudes (39°N). During all the flights, moderate amounts of NO 2 (0.7–2·10 15 /cm 2 ), elevated amounts of HNO 3 (1.75–2.35·10 16 /cm 2 ), ClNO 3 (2.4–5.4·10 15 /cm 2 ), and OClO (6–13·10 12 /cm 2 ) were found inside the vortex, indicating that the air masses of the vortex were still chemically disturbed. The observation is interpreted as the polar vortex going from the stage of its wintertime denoxification (conversion of NO x into NO y ;) and chlorine activation (conversion of HCl and ClNO 3 into chlorine oxides) to the springtime reverse processes via the formation of enhanced amounts of ClNO 3 . In addition, first measurements of OClO (6–10 12 /cm 2 at solar zenith angle 90°) and high amounts of ClNO 3 (4–10 15 /cm 2 ) around 40°N are reported.
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Pfeilsticker et al. (1997) studied this question.
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