A test of our understanding of the ozone chemistry in the Arctic polar vortex based on in situ measurements of ClO, BrO, and O-3 in the 1994/1995 winter

We present an analysis of in situ measurements of ClO, BrO, O-3, and long-l ived tracers obtained on a balloon flight in the Arctic polar vortex launch ed from Kiruna, Sweden, 68 degrees N, on February 3, 1995. Using the method of tracer correlations, we deduce that the air masses sampled at an altitu de of 21 km (480 K potential temperature), where a layer of enhanced ClO mi xing ratios of up to 1150 parts per trillion by volume was observed, experi enced a cumulative chemical ozone loss of 1.0+/-0.3 ppmv between late Novem ber 1994 and early February 1995, This estimate of chemical ozone loss can be confirmed using independent data sets and independent methods. Calculati ons using a trajectory box model show that the simulations underestimate th e cumulative ozone loss by approximately a factor of 2, although observed C lO and BrO mixing ratios are well reproduced by the model. Employing additi onal simulations of ozone loss rates for idealized conditions, we conclude that the known chlorine and bromine catalytic cycles destroying odd oxygen with the known rate constants and absorption cross sections do not quantita tively account for the early winter ozone losses infered for air masses obs erved at 21 km.