ATMOS ATLAS-3 MEASUREMENTS OF STRATOSPHERIC CHLORINE AND REACTIVE NITROGEN PARTITIONING INSIDE AND OUTSIDE THE NOVEMBER 1994 ANTARCTIC VORTEX/

Partitioning between HCl and ClONO2 and among the main components of t he reactive nitrogen family (NO, NO2, HNO3, ClONO2, N2O5, and HO2NO2) has been studied inside and outside the Antarctic stratospheric vortex based on ATMOS profiles measured at sunrise during the 3-12 November 1994 ATLAS-3 Shuttle mission. Elevated mixing ratios of HCl in the low er stratosphere with a peak of similar to 2.9 ppbv (10(-9) parts per v olume) were measured inside the vortex near 500 K potential temperatur e (similar to 19 km). Maximum ClONO2 mixing ratios of similar to 1.2, similar to 1.4, and similar to 0.9 ppbv near 700 K (similar to 25 km) were measured inside, at the edge, and outside the vortex, respectivel y. Model calculations reproduce the higher levels of HCl and NOx (NO NO2) inside the lower stratospheric vortex both driven by photochemic al processes initiated by low O-3. The high HCl at low O-3 results fro m chemical production of HCl via the reaction of enhanced Cl with CH4, limited production of ClONO2, and the descent of inorganic chlorine f rom higher altitudes.