1. DOAS Retrievals of Stratospheric O 3 and NO 2 from Odin / OSIRIS Limb-Radiance Measurements Samuel Brohede Craig S. Haley and the Odin team Chalmers University of Technology and York University

2. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 OSIRIS onboard Odin Odin SMROSIRIS OSIRI OSIRIS = Optical Spectrograph and InfraRed Imager System SMR = Sub Millimeter Radiometer

3. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Odin orbit specifications E Polar orbiting E Sun synchronous E Near terminator E 18.00 ascending node E Altitude ~600 km E Limb scanning between 7 and 70 km

4. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 The Optical Spectrograph E Wavelengths: 280-800 nm (UV-Vis) E Resolution: ~1 nm  FOV: 1 km vertical, 40 km horizontal OSIRIS

5. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 OS spectra from one scan O 3 windowNO 2 window

6. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 DOAS analysis Differential Optical Absorption Spectroscopy E Differential cross sections,  ’, are used.  ’’ smoothed cross section E Smoothing: Polynomial or Boxcar

7. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Advantages of DOAS E Broad features like Mie and Rayleigh- scattering does not need to be modelled E No need to estimate real I 0 / self calibrated E Multiple species can be measured simultaneously E High th spectrum (reference) used as I 0

8. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 DOAS windows O 3 windowNO 2 window

9. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 DOAS Least Squares Fit

10. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 The I 0 -effect E Structures in the reference spectrum (I 0 ). E Ratioing does not cancel out. E Taking care of in the x-sections convolution.

11. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 The Ring effect E Filling in of Fraunhofer and Telluric lines E Two approaches: 1 Backward modelling [ Sioris et al ] 2 Pseudo absorber [ Chance et al ] E Including Ring corr. did not improve the fit.

12. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Polarization E Differential structures in response for perp. light E Included as a pseudo absorber in O 3 -window

13. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Tilt/Undersampling E Different tilt of reference and measured spectra + Fraunhofer structures + undersampling => ratioing won’t cancel out. E Included as a pseudo absorber in NO 2 -window

14. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 T-dependent x-sections E Two possible approaches: 1) Use T at tangent height 2) Non linear fit for T E Only important for NO 2 -window

15. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Wavelength shift E Calibration differences between the OS and cross sections. E Taking care of in a non-linear fit E Only important in the NO 2 -window E No stretching/squeezing corrections

16. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Retrieval procedure Effective column density, c(th) Vertical number density, n(z) [ molecules cm -2 ] [ molecules cm -3 ]

17. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Optimum Estimation (MAP) E A Priori climatology [ McLinden ] E Non linear iteration E RTM = LIMBTRAN pseudo-3D [ Griffoen ]

18. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Calculating K and F E K and F are calculated numerically E CPU-Time consuming calculations E Two approaches: 1) 2- DOAS (ok for K in O 3 -window) 2) Sparse wavelength grid

19. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Method summary O 3 -regionNO 2 -region Wavelengths:571-617 nm435-451 nm Species:O 3, NO 2, O 4 O 3, NO 2, O 4 Corrections:I 0, PolI 0, Tilt, T-dep, -shift Ref. height:50 km50 km Estimating K:2- 2.5 nm step Estimating F: 4 nm step1 nm step Alt range:~15-40 km~20-35 km

20. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 O 3 -Results

21. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 NO 2 -Results

22. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Off-plane orbit

23. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Ozone hole splitting

24. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Comparison 3 March 2002 OSIRIS: lat:68.1 o N lon:10.6 o W 17:23 UTC POAM III: lat:67.5 o N lon:20.5 o W 18:27 UTC

25. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Comparison 8 Aug 2001 OSIRIS: lat:76.9 o N lon:13.8 o E 10:59 UTC Sonde: lat:78.9 o N lon:11.9 o E 10:59 UTC

26. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Comparison 22 Aug 2001 OSIRIS: lat:28.9 o N lon:16.1 o W 18:48 UTC Sonde: lat:28.3 o N lon:16.5 o W 11:17 UTC

27. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Comparison Paired Radiances DOAS Percentage difference Zonal means Nov 18 2001

28. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Comparison Paired Radiances DOAS Percentage difference Zonal means Nov 3 2002

29. 1st International UV/Vis Limb-Scattering workshop, Bremen, April 2003 Conclusions and outlook E O 3 compares well to Flittner and sondes E NO 2 looks promising E Further validation needed E Article soon submitted