MILLIMETER-WAVE SPECTROSCOPIC MEASUREMENTS OVER THE SOUTH-POLE .4. O-3 AND N2O DURING 1995 AND THEIR CORRELATIONS FOR 2 QUASI-ANNUAL CYCLES

In two separate papers we have previously reported observations of str atospheric O-3 and N2O over the South Pole during the 1993 annual cycl e. Here we present (1) new O-3 and N2O observations at the South Pole in 1995 and (2) correlations between O-3 and N2O for two 11-month obse rvations during February 1993 to January 1994 and January-December 199 5. Strong similarities exist between the two quasi-annual cycles for b oth O-3 and N2O. A double-peaked profile again dominates O-3 vertical distribution in 1995 as in 1993. Features such as a pronounced summer- fall decline in mid-stratospheric O-3 followed by an early winter incr ease, a downward trend in the O-3 contour pattern associated with vert ical transport, a transient enhancement of middle to upper stratospher ic O-3 just before local sunrise, the timing of the ozone hole onset, and a dramatic increase of stratospheric O-3 during and following vort ex breakup all show good consistency between the two annual cycles. N2 O observations show a good agreement between the two 11-month cycles i n atmospheric descent rate during fall and winter, and in the timing o f N2O recovery from diminished values during spring. We use O-3-N2O co rrelations to further investigate the double-peaked vertical distribut ion of O-3. During springtime warmings the O-3/N2O ratio shows a tight coupling between O-3 and N2O around 20 km, as transport creates the l ow-altitude O-3 peak. A rapid and systematic decrease of the O-3/N2O r atio during summer in the 25 to 30 km region (while N2O is essentially stable) supports the increasingly dominant role of photochemistry in producing the vertical profile for O-3 above -25 km while leaving a tr ansport-produced layer with a relatively large mixing ratio below simi lar to 25 km. The resulting double-peaked O-3 distribution, which pers ists for many months, can alter the normally negative correlations bet ween O-3 and N2O in the lower and middle stratosphere, although in mea surements of the N2O/O-3 ratios for polar air these perturbations have often been taken to be a hallmark of catalytic ozone depletion by chl orine. The present analysis should help to clarify the influence of th e relatively unique O-3 vertical distribution of polar ozone when inte rpreting O-3-N2O correlations.