Balloon-borne in situ measurements of CLO and ozone: Implications for heterogeneous chemistry and mid-lattitude ozone loss (original) (raw)

In situ measurements of chlorine oxide (C10) obtained on 31 March 1991 with a new balloon-borne instrument are compared to results from a photochemical model which incorporates hydrolysis of N2Os on sulfate aerosols. With the addition of this process, there is better agreement between calculation and measurement over most of the profile, except below 20 km where observed C10 is greater by as much as a factor of four. In a model which is constrained to reproduce the observed C10 below 20 km, ozone loss by catalytic cycles involving halogen oxides becomes larger than that from NOx, which would dominate under gas-phase or standard heterogeneous conditions. reasons. The balloon-borne measurements of C10 made in the late 1970's and 1980's were all obtained over eastern Texas and display significant variability, thus providing little insight into seasonal, latitudinal or secular trends [WMO, 1985]. More recent data from ER-2 flights at mid-latitudes have exhibited considerably less variability and have been examined for seasonal and latitudinal effects [Rodriguez et al., 1991; Toohey et al., 1991; King et al., 1991 ]. These studies have shown that models which include only gas-phase chemistry cannot reproduce the observations. On the other hand, incorporation of heterogeneous processes which reduce NOx (--NO + NO2) in fa-The performance of a new instrument for in situ measurements of C10 in the lower stratosphere, Geophys. Res. Lett., this issue, 1993. Weinstock, E.M., C.M. Schiller and J.G. Anderson, In situ stratospheric ozone measurements by long path UV absorption: developments and interpretation, J. Geophys. Res., 91, 5237-5248, 1986. of transport on column abundances of nitrogen and chlorine compounds in the Arctic stratosphere, Geophys. Res. Lett., 17, 533-536, 1990.