Airborne heterodyne measurements of stratospheric ClO, HCl, O-3, and N2O during SESAME 1 over northern Europe

Vertical distributions of ClO, HCl, N2O, and O-3 have been retrieved from airborne observations of pressure-broadened emission spectra in the frequency range of 620 to 690 GHz. Observations were made in February 1994 in the Arctic stratosphere above northern Europe with the Airborne Submillimeter SIS Radiometer (ASUR) during the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME) 1 campaign. ASUR is the first airborne submillimeter experiment to employ the new superconductor-insulator-superconductor (SIS) receiver technology for stratospheric ozone research. Owing to meteorological conditions, all observations were made outside the polar vortex. The retrieved volume mixing ratio (VMR) profiles show a good agreement with observations made by the submillimeter limb sounder (SLS) operated by the Jet Propulsion Laboratory (JPL) (Pasadena) and the Kern Forschungs Anlage (KFA) (Julich). A comparison between retrieved VMR profiles and profiles obtained from the SLIMCAT three-dimensional stratospheric chemistry model also shows a good agreement. Two ClO emission lines, at 649 and 686 GHz, respectively, are shown to be equally adequate lines for observation purposes. An anticorrelation has been found between the N2O and HCl VMR values, and also between the N2O and ClO VMR values. The correlations between N2O and HCl do not show the relatively low HCl VMR values correlated to relatively low N2O values as shown by Webster et al. [1994].