Simultaneous profile measurements of BrO, OClO and NO 2 in the polar vortex Chris Sioris and Kelly Chance Smithsonian Astrophysical Observatory

Method: Two-step retrieval Step 1: Spectral fit BrO (Wilmouth et al.) OClO (Wahner et al.) NO 2 and O 3 (Bogumil et al., 203, 223, 243 K) tilt (Sioris et al., uses Chance-Kurucz solar spectrum)

Sample fitted optical depths, BrO fitting window, at TH=10 km in Arctic vortex

Step 2: Vertical “fitting” of SCD profile -pointing correction: 305 nm knee -Forward RTM: McLinden et al., inversion: modified Chahine’s method (Sioris et al., 2003) for OClO, retrieval is done on a 1 km altitude grid using measurement TH grid (~3.3 km sampling)

NO 2 Validation Typical agreement based on comparisons with OSIRIS, SAGE III, SAOZ, and HALOE is 7% on VCD and 14% profile (15-41 km)

BrO validation BrO VCD (15-27 km) agrees to <5% and profile to 7% with SAOZ-BrO (despite poor temporal coincidence of ~10 hours) At ~23 km, BrO: 26 pptv (10 am LT), pptv (before sunset, ascent)

Top: SCIAMACHY NO 2 number density, cm -3, on August 5, 2002; Bottom: Canadian Middle Atmosphere Model NO 2 [de Grandpre et al., 1997]. Sample orbit of NO 2

Sample orbit of BrO- July 24th pptv -Tropical upper tropospheric BrO at 4 ° S, associated with cirrus -Latitudinal distribution as expected [BrO]  18 pptv in the middle stratosphere

SCIA OS Feb. 2003: Arctic

Artic, Feb. 10th, 2003: DeNO x ification extends from ~18-28 km

OSIRIS (17-37 km) LT: just after sunrise (SZA  87.5°) SCIAMACHY (15-41 km) SZA (am) molec/cm 3 Effect of differences in across-track and vertical resolution

Noxon cliff at 50° N

 SCIA VCD=3.53e13  SCIA VCD= 1.02e13

Arctic OClO, Feb. 10th, 2002

Arctic BrOVCD (15-27 km, molec/cm 2 ) 61º: 3.4e13 68º: 2.3e13 72º: 5.3e13 75º: 5.7e13 OS VCD 3.4e13

PSC observation, 65° S in early August (orbit 2293) Data from Antarctic winter

PSC at ~20-24 km, August 23rd, 61° S (orbit 2508)

Lat(°S) SCIA VCD (11-41 km) e e e14

-DeNO x ification extends from 14  34 km at 68° S, 17  30 km at 61° S -local sunrise, so NO 2 is at daytime minimum (variation above is partly diurnal) -at 27 km, 68° S, [NO 2 ] at sunrise is 2  10 7 molec/cm 3,  [OClO], [BrO] -hint of NO x descending from the mesosphere at 68° S

* * Lat SCIA (°S)VCD (14-28 km) e e13

Lat SCIA (  S) VCD (11-30 km) e e e13

Evidence for high BrO mixing ratios in middle stratosphere, at high southern latitudes as well

Direct confirmation of our understanding of BrO photochemistry in the lower stratosphere at sunrise [BrO] sharply decreasing with height in the lowermost stratosphere BrO spike at ~19 km “allowed” by low NO 2 at 68° S

Conclusions OClO layer peaks at higher altitude in Antarctic than Arctic at the vortex edge, OClO shows a very limited vertical extent (sharp layer) Denoxification is more severe and covers a greater altitude range in Antarctic than Artic OClO exhibits correlation with BrO and clear anti-correlation with NO 2 ; BrO also anti-correlated with NO 2 SCIAMACHY stratospheric BrO is in good agreement with GOME total columns outside of polar PBL enhancements BrO mixing ratios of 26 pptv in the middle stratosphere!!!

Acknowledgments Florence Goutail and the SAOZ team, Ghassan Taha and the SAGE III team, Michel van Roozendael (IASB), University of Bremen, and Chris McLinden (Environment Canada) Final Remark Limb scatter technique can measure scientifically useful profiles of minor trace gases such as BrO and OClO despite their absorption signatures being at the level