Distribution and seasonal variation of CFCS in the stratosphere: Comparison of satellite global data and a 2-D model

Abstract

The Cryogenic Limb Array Etalon Spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite obtained global distributions of CF 2Cl 2 and CFCl 3 in the stratosphere between October 1991 and May 1993. This paper discusses the seasonal and interannual behavior of a number of prominent dynamical features observed in the zonal mean fields for both gases over the period January 1992 through February 1993 and compares these features with a two-dimensional model. The CFC fields are shown to exhibit many of the same seasonally variant features seen in other conserved tracer fields. These include a semiannual oscillation signature in the tropical upper-level mixing ratios; the development of a double-peaked tropical structure near the vernal equinox and its weakening, or absence, at the autumnal equinox; steep descent at winter high latitudes in both hemispheres with an associated midlatitude surf zone, which is stronger and more sustained in the southern hemisphere; and sharp subtropical gradients in the mixing ratio isopleths in the northern winter hemisphere. Distinct interannual variability is also observed in the CF 2Cl 2 morphology, particularly for the northern hemisphere for the periods January–February 1992 and 1993. Other than this latter feature, the two-dimensional model is generally found to reproduce the observed behavior, although usually with weaker manifestation than seen in the data, especially in regard to the double-peaked equinoctial structure.