FIRST DIRECT SIMULTANEOUS HCL AND CLONO2 PROFILE MEASUREMENTS IN THE ARCTIC VORTEX

Coincident vertical profiles of HCl and ClONO2 in the Arctic vortex ha ve been retrieved simultaneously in the altitude range 13 to 31 km. So lar occultation spectra were recorded, during both ascent and occultat ion, with a balloon-borne infrared Fourier transform spectrometer laun ched on 22 March 1995 from Kiruna (Sweden, 67 degrees N, 22 degrees E) . A depleted layer of HCl is observed between 16 and 18 km, whereas Cl ONO2 is showing values larger than 2 ppbv around 20 km. The impact on the derived total inorganic chlorine of a 20% increase of the current ClONO2 absolute line intensities is discussed. These first direct meas urements of the mixing ratio profiles of HCl and ClONO2 are compared w ith the results of the REPROBUS chemistry transport model and discusse d in term of chlorine partitioning.