Aircraft-borne detection of stratospheric column amounts of O3, NO2, OClO, ClNO3, HNO3, and aerosols around the arctic vortex (79°N to 39°N) during spring 1993: 1. Observational data

Using several remote sensing techniques on board a research aircraft (Transall C‐160), we measured the stratospheric column amounts of O3, NO2, OClO, ClNO3, and HNO3, 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 NO2 (0.7–2·1015/cm2), elevated amounts of HNO3 (1.75–2.35·1016/cm2), ClNO3 (2.4–5.4·1015/cm2), and OClO (6–13·1012/cm2) 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 NOx into NOy;) and chlorine activation (conversion of HCl and ClNO3 into chlorine oxides) to the springtime reverse processes via the formation of enhanced amounts of ClNO3. In addition, first measurements of OClO (6–1012/cm2 at solar zenith angle 90°) and high amounts of ClNO3 (4–1015/cm2) around 40°N are reported.