Atmospheric Chemistry and Physics Diurnal variations of reactive chlorine and nitrogen oxides observed

Abstract. The winter 2009/2010 was characterized by a strong Arctic vortex with extremely cold mid-winter tem-peratures in the lower stratosphere associated with an in-tense activation of reactive chlorine compounds (ClOx) from reservoir species. Stratospheric limb emission spectra were recorded during a flight of the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) from Kiruna (Sweden) on 24 January 2010 in-side the Arctic vortex. Several fast limb sequences of spectra (in time steps of about 10 min) were measured from night-time photochemical equilibrium to local noon allowing the retrieval of chlorine- and nitrogen-containing species which change rapidly their concentration around the terminator be-tween night and day. Mixing ratios of species like ClO, NO2, and N2O5 show significant changes around sunrise, whic