AN ANALYSIS OF HALOE OBSERVATIONS IN SUMMER HIGH-LATITUDES USING AIRMASS TRAJECTORY AND PHOTOCHEMICAL MODEL-CALCULATIONS

Stratospheric ozone, HCl, NO, and NO2 observed by the Halogen Occultat ion Experiment (HALOE) on the Upper Atmosphere Research Satellite (UAR S) in late summer at high latitudes show nonuniform distributions in t heir volume mixing ratios along a latitude circle, while the mixing ra tios of the long-lived tracers; such as CH4 and HF, are observed to be quite uniform. These anomalous distributions of the reactive gases ar e confined in approximately 20-35 km, It is found that in the summer h igh latitudes, the isosurfaces of long-lived tracers nearly coincide w ith isentropes. On the basis of meridional distributions of these spec ies, it appears that the HALOE-observed features are the results of qu asi-isentropic transport across latitude lines with a timescale shorte r than the chemical relaxation times of those HALOE observed ozone and other gases, A spectral analysis of the United Kingdom Meteorological Office meridional wind data indicates the existence of episodically a mplified wave 1 that is quasi-stationary in July and then slowly westw ard moving after mid-August 1992. A quasi-stationary wave 2 is also fo und to be important in late August, The isentropic trajectory calculat ions show that these planetary scale waves seem to pull air masses out of the polar region as far as 10 degrees-15 degrees latitude equatorw ard in a week, Midlatitude sir is also pushed into the high summer lat itude region, A photochemical box model is used to simulate the chemic al evolution of HALOE-observed species along air parcel trajectories w hich are initialized at HALOE positions. Reasonable agreement is found in comparisons between coincident HALOE measurements and the model re sults in later days. The characteristic structures in HALOE-observed o zone and other gases in the low and middle stratosphere indicate that the chemical relaxation times taken for these species to relax to thei r new local mixing ratios under new sunlit conditions are comparable w ith or longer than the timescale of the meridional transport induced b y waves in late summer.