Simultaneous profile measurements of BrO, OClO and

NO2 in the polar vortex

Chris Sioris and Kelly ChanceSmithsonian Astrophysical

Observatory

Method: Two-step retrieval

Step 1: Spectral fit

-2.40

-2.35

-2.30

-2.25

-2.20

-2.15

342 344 346 348 350 352 354 356 358 360 362

Wavelength (nm)

ln(I

0/I)

fit obs

Retrieved gas Interference fitting window (nm) # of pixels polynomial I0 TH range (km)BrO NO2, O3, tilt, -shift 344.09-360.03 146 cubic 33-70OClO BrO, NO2, O3, tilt, -shift 357.37-381.12 224 cubic 33-70NO2 O4, O3, -shift, Ring 434.63-494.87 255 cubic 46-70

BrO (Wilmouth et al.) OClO (Wahner et al.) NO2 and O3 (Bogumil et al., 203, 223, 243 K)tilt (Sioris et al., uses Chance-Kurucz solar spectrum)

-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

344 346 348 350 352 354 356 358 360

BrOO3tiltNO2

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

Modelled and measured SCDs

BrO SCD (molec/cm2)

0 1e+14 2e+14 3e+14 4e+14 5e+14 6e+14

TH (k

m)

10

12

14

16

18

20

22

24

26

28

modelledmeasured

Step 2: Vertical “fitting” of SCD profile

-pointing correction: 305 nm knee-Forward RTM: McLinden et al., 2002-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)

Retrieved gas TH range (km) z range (km) SCD err #D err VCD errBrO 10-33 15-29 ~20% <55% <30%OClO 15-29 15-27 20% <30% <30%NO2 10-42 11-41 <1% <6% <2%

75 N, Oct. 26th, 2002

NO2 number density (molec/cm3)

0.0 2.0e+8 4.0e+8 6.0e+8 8.0e+8 1.0e+9 1.2e+9 1.4e+9 1.6e+9 1.8e+9

Alti

tude

(km

)

20

22

24

26

28

30

32

34

36

38

40

SAGE III SCIA SZA=90º SCIA w/kn SZA=86º SCIA 86 w/o kn

NO2 Validation

Typical agreement based on comparisons with OSIRIS, SAGE III, SAOZ, and HALOE is 7% on VCD and 14% profile (15-41 km)

Aire sur l'Adour (43.7º N 0.3º E), Oct 1st, 2002

BrO number density (cm-3)0 1e+7 2e+7 3e+7 4e+7 5e+7 6e+7

Alti

tude

(km

)

14

16

18

20

22

24

26

28

30

SCIAMACHY (SZA=58°, am)SCIAMACHY (SZA=83°, pm) SAOZ-BrO (SZA=83°, pm) SAOZ (SZA=83°, pm)

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), 16-20 pptv (before sunset, ascent)

50

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7

5

3

80 74 66 59 51 44 36 28 20 13 6 -2 -10

-18

-25

-33

-41

-48

-56

Pre

ssur

e (m

b)

Latitude (º)

0.0E+0

5.0E+8

1.0E+9

1.5E+9

2.0E+9

2.5E+9

50

30

20

15

10

7

5

3

80 74 66 59 51 44 36 28 20 13 6 -2 -10

-18

-25

-33

-41

-48

-56

Pre

ssur

e (m

b)

Latitude (º)

0.0E+0

5.0E+8

1.0E+9

1.5E+9

2.0E+9

2.5E+9

Top: SCIAMACHY NO2 number density,cm-3, on August 5, 2002;

Bottom: Canadian Middle AtmosphereModel NO2 [de Grandpre et al., 1997].

Sample orbit of NO2

Sample orbit of BrO- July 24th

1112131415161718192021222324252627

Latitude (°)

0

5

10

15

20

25

30

35

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: DeNOxification extends from ~18-28 km

11131517192123252729313335373941

0.E+00 1.E+08 2.E+08 3.E+08 4.E+08 5.E+08 6.E+08 7.E+08 8.E+08 9.E+08 1.E+09

NO2 number density (molec/cm3)

Altit

ude

(km

)

75 N 72 N OS 72 N 68 N

1517192123252729313335373941

75 72 68 60Latitude (°)

0.0E+ 0

1.0E+ 8

2.0E+ 8

3.0E+ 8

4.0E+ 8

5.0E+ 8

6.0E+ 8

OSIRIS (17-37 km)

LT: just after sunrise(SZA 87.5°)

SCIAMACHY (15-41 km)

89.7 87 84 77 SZA (am)

1719

21

23

2527

2931

33

35

37

72 71 67 63 58Latitude (°)

0.0E+ 0

1.0E+ 8

2.0E+ 8

3.0E+ 8

4.0E+ 8

5.0E+ 8

6.0E+ 8

molec/cm3

Effect of differences in across-track and verticalresolution

VCDs from both instruments (Feb. 10th, 2003)

Latitude (°)

5658606264666870727476

NO

2 V

CD

(x 1

014 m

olec

/cm

2 )

2

4

6

8

10

12

OSIRIS (17-37 km)SCIAMACHY (15-41 km)

17

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2931

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35

37

72 71 67 63 58 53 48Latitude (°)

0.0E+ 0

1.0E+ 8

2.0E+ 8

3.0E+ 8

4.0E+ 8

5.0E+ 8

6.0E+ 8

7.0E+ 8

8.0E+ 8

Noxon cliff at 50° N

---------------------------------SCIA VCD=3.53e13

-------SCIA VCD= 1.02e13

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27

0 5 10 15 20 25 30

Volume mixing ratio (ppt)

Alti

tude

(km

)

75 N, SZA=89.7° 71.5 N, SZA=86.6°

15

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25

27

0.E+00 1.E+07 2.E+07 3.E+07 4.E+07 5.E+07 6.E+07 7.E+07 8.E+07

OClO number density (cm-3)

Alti

tude

(km

)

75 N72 N

ArcticOClO,Feb. 10th,2002

Northern hemisphere winter 02/03

OClO volume mixing ratio (pptv)

0 10 20 30 40 50 60

Alti

tude

(km

)

10

15

20

25

30

4225s2 (Dec. 21, 61° N, SZA=85.2), no PSC 4225s1 (Dec. 21, 64° N, SZA=88.6°), no PSC 4956s5 (Feb. 10, 75° N, SZA=86.6°), no PSC 4965s6 (Feb. 10, 72° N, SZA=89.7°) no PSC

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29

0.E+00 1.E+07 2.E+07 3.E+07 4.E+07 5.E+07 6.E+07 7.E+07 8.E+07 9.E+07

BrO number density (molec/cm3)

Alti

tude

(km

)

68 N 72 N 75 N OS 72 N

Arctic BrO

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29

0 5 10 15 20 25 30 35 40 45

BrO mixing ratio (pptv)

Alti

tude

(km

)

68 N72 N75 NOS 72 N

VCD (15-27 km, molec/cm2)

61º: 3.4e1368º: 2.3e1372º: 5.3e1375º: 5.7e13

OS VCD3.4e13

Limb radiance profiles at 2 NIR s

0

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40

0.0E+00 2.0E+03 4.0E+03 6.0E+03 8.0E+03 1.0E+04 1.2E+04 1.4E+04

Radiance (arb. u.)

TH

(km

)

1301.241093.22

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

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

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1.3E+04 1.8E+04 2.3E+04 2.8E+04 3.3E+04 3.8E+04

Radiance at 1196 nm (arb.u.)

TH (

km)

••

•

Lat(°S) SCIA VCD

(11-41 km) 54 1.63e15 61 7.38e14 68 2.43e14

-DeNOxification extends from 1434 km at 68° S, 1730 km at 61° S-local sunrise, so NO2 is at daytime minimum (variation above is partly diurnal)-at 27 km, 68° S, [NO2] at sunrise is 2107 molec/cm3, [OClO] , [BrO]-hint of NOx descending from the mesosphere at 68° S

11131517192123252729313335373941

0.0E+00 2.0E+08 4.0E+08 6.0E+08 8.0E+08 1.0E+09 1.2E+09

NO2 number density (molec/cm3)

Altit

ude

(km

)

54 S, SZA=76 61 S, SZA=83 68 S, SZA=89.9

Southern hemisphere winter, 2002

OClO volume mixing ratio (pptv)

0 5 10 15 20 25 30 35

Alti

tude

(km

)

10

15

20

25

30

35

2794s6 (Sep. 12, 75° S, SZA=89.6°), no PSC 2293s3 (Aug. 8, 65° S, SZA=89.997°), PSC at 23 km 2297s9 (Aug. 8, 65° S, SZA=89.9°), no PSC2337s16 (Aug. 11, 65° S, SZA=89.9°), no PSC2307s3 (Aug. 11, 65° S, SZA=89.96°)2508s4 (Aug. 23, 68° S, SZA=89.77°), no PSC2508s3 (Aug. 23, 61° S, SZA=83.0°), PSC at 23 km2250bs2 (Aug. 5, 59.5° S, SZA=86°), no PSC 2579s5 (Aug. 28, 66° S, SZA=85.3°), no PSC

**

Lat SCIA (°S) VCD (14-28 km)61 7.6e1268 1.5e13

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30

0 5 10 15 20 25 30 35

OClO volume mixing ratio (pptv)

Alti

tude

(km

)

14

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26

28

30

0.0E+00 5.0E+06 1.0E+07 1.5E+07 2.0E+07 2.5E+07

OClO number density (cm-3)

Alti

tude

(km

)

68 S61 S

••

•Lat SCIA(S) VCD (11-30 km)54 5.48e13 61 5.83e1368 3.30e13

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

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29

0 5 10 15 20 25 30 35

BrO mixing ratio (pptv)

Alti

tude

(km

)

68 S, SZA=89.761 S, SZA=82.854 S, SZA=76

•Direct confirmation of our understanding of BrO photochemistryin the lower stratosphere at sunrise

•[BrO] sharply decreasing with height in the lowermost stratosphere•BrO spike at ~19 km “allowed” by low NO2 at 68° S

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0.0E+00 1.0E+07 2.0E+07 3.0E+07 4.0E+07 5.0E+07 6.0E+07 7.0E+07

BrO number density (molec/cm3)

Alti

tude

(km

)

68 S, SZA=89.761 S, SZA=8361 S, SZA=89.7

ConclusionsConclusions

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-correlationwith NO2 ; BrO also anti-correlated with NO2

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!!!

AcknowledgmentsAcknowledgments

Florence Goutail and the SAOZ team, Ghassan Taha and the SAGE IIIteam, Michel van Roozendael (IASB), University of Bremen, and

Chris McLinden (Environment Canada)

Final RemarkFinal 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 10-3 level