ESTIMATES OF TOTAL ORGANIC AND INORGANIC CHLORINE IN THE LOWER STRATOSPHERE FROM IN-SITU AND FLASK MEASUREMENTS DURING AASE-II

Aircraft sampling has provided extensive in situ and flask measurement s of organic chlorine species in the lower stratosphere. The recent Ai rborne Arctic Stratospheric Expedition II (AASE II) included two indep endent measurements of organic chlorine species using whole air sample and real-time techniques. From the whole air sample measurements we d erive directly the burden of total organic chlorine (CCly) in the fewe r stratosphere. From the more limited real-time measurements we estima te the CCly burden using mixing ratios and growth rates of the princip al CCly species in the troposphere in conjunction with results from a two-dimensional photochemical model. Since stratospheric chlorine is t ropospheric in origin and tropospheric mixing ratios are increasing, i t is necessary to establish the average age of a stratospheric air par cel to assess its total chlorine (Cl-Total) abundance. Total inorganic chlorine (Cl-y) in the parcel is then estimated by the simple differe nce, Cl-y = Cl-Total - CCly. The consistency of the results from these two quite different techniques suggests that we can determine the CCl y and Cl-y in the lower stratosphere with confidence. Such estimates o f organic and inorganic chlorine are crucial in evaluating the photoch emistry controlling chlorine partitioning and hence ozone loss process es in the lower stratosphere.