TWILIGHT VARIATION OF VERTICAL COLUMN ABUNDANCES OF OCLO AND BRO IN THE NORTH POLAR-REGION

Meaurements of vertical column abundances of OClO and BrO obtained during the Airborne Arctic Stratospheric Expedition 1989 are used for comparison with simple model calculations. The diurnal variation of these molecules is examined using data taken during morning and evening twilight and during nighttime. The comparison suggests that air masses inside the Arctic vortex contain ClO mixing ratios of several 100 pptv and in some cases up to 600 pptv, in agreement with in situ measurements. The measured OClO and BrO vertical column abundances are consistent with BrO mixing ratios of 7-12 pptv. The magnitude as well as the variation of the measured OClO and BrO vertical column abundances during twilight agree in most cases with the calculated vertical column abundances. Nevertheless, the model calculations are inconsistent with the observed high nighttime BrO vertical column abundances of 6-10 x 10(13) cm-2.