Anna Serdyuchenko, Victor Gorshelev, Wissam Chehade, John P. Burrows, Mark Weber

1. Anna Serdyuchenko, Victor Gorshelev, Wissam Chehade, John P. Burrows, Mark Weber University of Bremen, Institute for Environmental Physics Harmonization of GOME, SCIAMACHY, GOME-2 ozone cross-sections: final results from laboratory measurements HARMONICS Final Meeting - ESRIN, Frascati

2. Agenda • 1. HARMONICS project goals • 2. Measurements of cross-section in laboratory: setup • 3. Results analysis • 4. Outlook HARMONICS Final Meeting - ESRIN, Frascati

3. HARMONICS project goals • New measurements of cross-section in laboratory • Results analysis 1. HARMONICS project goals HARMONICS Final Meeting - ESRIN, Frascati

4. Cross-section issues in satellite DOAS: directcomparisonswith BMD 326.6-334.5 nm Direct comparison by fitting cubic polynomial (DOAS type), a wavelength shift, and Gaussian slit function to match DBMto other cross-sections: • SCIAMACHY FM requires a scaling of +5% and GOME2 FM of +7%wrt to GOME in TO3 retrieval (Eskes et al., 2005, Lerot et al., 2009, Weber et al., 2011) • There are significant shifts between cross-sections (FMs and Bass-Paur), • Note: total ozone change is -6DU/0.01nm shift (or -2%/0.01 nm) !!! • advantage of satellite FMs: ILS does not need to be known • disadvantage of satellite FM: Measurements were done at external facility under high time pressure (satellite calibration period) • Weber et al., 2011 HARMONICS Final Meeting - ESRIN, Frascati

5. Retrieval issues related to cross-sections • SCIAMACHY total O3 retrieval (using SCIAMACHY FM reference spectra) were 5% higher than GOME (with GOME FM reference spectra) in the range 325-335 nm (5% direct cross-sections scalingwrt. GOME FM). • GOME2 total O3 retrieval (using GOME2 FM3) is 9% higher than calculated with resolution adjusted GOME FM. (7% direct cross-sections scalingwrt. GOME FM). • Harmonisation of O3 and NO2 FM cross-sections from GOME and SCIAMACHY for a consistent retrieval. • Two approaches: • reanalysis of data from the CATGAS campaigns; • new laboratory measurements. HARMONICS Final Meeting - ESRIN, Frascati

6. Work plan for HARMONICS • Re-analyse the satellite FM cross-section data based upon available raw data from the CATGAS campaigns (WP 100) • GOME FM: no raw data available  will remain unchanged • SCIAMACHY FM: raw measurement files are available  reanalysis • GOME-2 FM3: raw measurement files are available reanalysis • NO2: no need for change (stable gas conditions) Note: FM cross-section data are relative measurements (need to be scaled to reference data, here : BDM/BassPaur, alternative: new IUP) • New laboratory measurements at IUP at high spectral resolution (UV to near IR) • Verification of new results and total ozone retrieval tests HARMONICS Final Meeting - ESRIN, Frascati

7. Current status of the available ozone cross-sections datasets • Importance of the cross-sections set choice is vigorously discussed last years within the ozone observing community. • Quantum mechanical approach: • a potential of producing a noise-free cross-sections. • however, the quality of the ab initio calculations is still inferior to the experimental data accuracy. • a comparison of calculated spectra with experimental high resolution data obtained in a wide spectral range at different temperatures should play an important role in such studies. • Experimentally obtained ozone absorption cross-sections from pioneer works (1932) until most recent studies: online spectral atlas of gaseous molecules of the Max‑Planck Institute for Chemistry, Mainz. • A large-scale initiative to review and recommend ozone cross-sections for all of the commonly used atmospheric ozone monitoring instruments was started in spring 2009. • Absorption Cross-sections of Ozone (ACSO) committee: a joint commission of the Scientific Advisory Group of the Global Atmosphere Watch of the World Meteorological Organization (WMO-GAW) and the International Ozone Commission (IO3C) of the International Association of Meteorology and Atmospheric Sciences. HARMONICS Final Meeting - ESRIN, Frascati

8. Current status of the available ozone cross-sections datasets 1. The high-resolution broadband data obtained by Bass and Paur (BP) : • cover spectral region of 245 nm to 343 nm only. • currently included in the standard ozone total column and profile retrievals using ground-based (Brewer, Dobson) and satellite (SBUV, TOMS V8) spectrometers. • included in the latest version of the high-resolution transmission molecular absorption database HITRAN 2008; however, a wavelength shift must be applied. 2. The high-resolution broadband data by Brion, Daumont, Malicet (BMD) • available for 195 nm - 830 nm for room temperature and for 194.5 nm - 520 nm for lower temperatures down to 218K. • subject of debates on substituting them for Bass and Paur data within the WMO-GAW and IGACO community and in the next version of the HITRAN dataset. • Currently data are used on the OMI and GOME GDP5 retrievals. 3. The high-resolution broadband cross-sections obtained by Bremen team • Temperature-dependent absorption cross-sections at230-830 nm were recorded with a Fourier-transform spectrometer. 4. Measurements at single wavelengths: Axson (2011), Anderson (1993), Enami (2004), El Helou (2005), Peterson (2012) HARMONICS Final Meeting - ESRIN, Frascati

9. Current status of the available ozone cross-sections datasets Recommendation on using the dataset on existing instruments and future missions is a subject for research of many ozone investigating groups and nets around the world. Nevertheless, few obvious criteria can be formulated: • spectral resolution at least order of magnitude better than the instrumental bandwidths of modern remote sensing spectrometers; • wide spectral region to include spectral channels and windows of as many instruments as possible; • availability of high quality experimental data at several temperatures going as low as 190K (ozone hole conditions). HARMONICS Final Meeting - ESRIN, Frascati

10. Current status of the available ozone cross-sections datasets Despite of the high quality of the already available data experimental works on the ozone absorption spectra continue. There are few important issues to be addressed: • improvement of the absolute accuracy of the cross-section up to 1-2% at least in the Huggins band to answer the requirement to measure small changes in stratospheric and tropospheric ozone; • improvement of the wavelength calibration; • improvement of the temperature dependence in the different spectral regions, especially in the Huggins and Wulf bands; • measurements of the weak absorption in the bottom of the Huggins and Chapuis bands and in the Wulf band NIR region longer than 900 nm, which were poorly covered so far. HARMONICS Final Meeting - ESRIN, Frascati

11. Demands on a modern dataset • wavelength coverage UV/VIS/NIR 200 – 1000 nm; • vacuum wavelength accuracy ~ 0.001 nm; • spectral resolution ~ 0.02 nm; • absolute intensities accuracy: 2%; • temperature: 193K-293 K, step 10K HARMONICS Final Meeting - ESRIN, Frascati

12. 2. Cross-section measurements in laboratory: set-up • HARMONICS project goals • New measurements of cross-section in laboratory • Results analysis HARMONICS Final Meeting - ESRIN, Frascati

13. Ozone cross sections at 213- 1100 nm Hartley Huggins Chappuis Wulf HARMONICS Final Meeting - ESRIN, Frascati

14. Main parameters of experimental set-ups HARMONICS Final Meeting - ESRIN, Frascati

15. Main parameters of experimental set-ups HARMONICS Final Meeting - ESRIN, Frascati

16. Accuracy and precision of the new data HARMONICS Final Meeting - ESRIN, Frascati

17. Accuracy and precision of the published data HARMONICS Final Meeting - ESRIN, Frascati

18. 3. Cross-section measurements in laboratory: results analysis • HARMONICS project goals • New measurements of cross-section in laboratory • Results analysis HARMONICS Final Meeting - ESRIN, Frascati

19. Hartley Huggins (DOAS) Chappuis NIR Wulf Minimum IR HARMONICS Final Meeting - ESRIN, Frascati

20. Results analysis • Polynomial dependence on temperature: • Bass-Paur parameterization (2nd order polynomial) for selected wavelengths in Huggins band • Band-integrated cross-sections as functions of temperature (insensitive to resolution) • Hartley, Huggins, Chappuis bands • Comparison with existing datasets • High resolution datasets: Bass – Paur , Brion et al : wavelength shift, absolute scaling factor • Low resolution satellite datasets: resolution matching, wavelength shift, absolute scaling factor • Total ozone retrieval (Wissam Chehade) Please note: comparison between cross-sections is not the same thing as comparison between retrievals results!!!! HARMONICS Final Meeting - ESRIN, Frascati

21. Results analysis • Nowadays, spectral channels of the satellites-based (GOME, GOME-2, SCIAMACHY, SAGE, SBUV, TOMS, OMI, OSIRIS) and ground based-instruments (Brewer, Dobson) measuring ozone and other trace gases cover a wide spectral range from near UV to the visible and IR. • Ozone absorption spectrum in near UV – near IR affects channels for detection of other traces gases, aerosols and clouds. HARMONICS Final Meeting - ESRIN, Frascati

22. Band-integrated cross-sections Results verification Hartley Mean values are taken from Orphal, J. (2003) A critical review of the absorption cross-sections of O3 and NO2 in the ultraviolet and visible. J. Photochem. Photobiol. A 157, 185-209; Estimated experimental uncertainty is ~2% Huggins (DOAS) Chappuis NIR IR Minimum HARMONICS Final Meeting - ESRIN, Frascati

23. Band-integrated cross-sections: temperature dependence Chappuis Hartley Wulf Huggins HARMONICS Final Meeting - ESRIN, Frascati

24. Comparison on wavelengths of remote sensing and ground based instruments • The spectral resolution of diverse ozone observing instruments changes: • with wavelength from the UV to the near IR • from channel to channel for each instrument. HARMONICS Final Meeting - ESRIN, Frascati

25. Comparison on wavelengths of remote sensing and ground based instruments • BMD and BP – interpolated at 293K; • All datasets – resolution downgraded 1 nm HARMONICS Final Meeting - ESRIN, Frascati

26. Comparison at Hg lamp and He-Ne laser lines, 293K HARMONICS Final Meeting - ESRIN, Frascati

27. Temperature dependence in UV region at 253.65 nm (Hartley band) • Very weak temperature dependence (within 1%) • Very good agreement with BMD, BP, GOME, SCIAMACHY FM revised, GOME-2 revised HARMONICS Final Meeting - ESRIN, Frascati

28. Huggins band, DOAS window HARMONICS Final Meeting - ESRIN, Frascati

29. Temperature dependence on selected wavelengths in Huggins band • No resolution matching • ‘Bass-Paur ’parametrisation • 328 nm “hill”, 330 nm “valley” • Black– New Data, Blue – BMD, • Magenta– SCIAMACHY HARMONICS Final Meeting - ESRIN, Frascati

30. New data vs BMD and SCIAMACHY (293K) HARMONICS Final Meeting - ESRIN, Frascati

31. Comparison in Huggins band region: new data versus high resolution datasets, relative difference and shifts • BP – Bass Paur, BMD – Brionet al • 2nd order polynomial inter/extrapolation 193-293K with step of 10K • inter/extrapolation on the common grid with step of 0.01 nm • no resolution matching needed • mean absolute deviation: • Green– comparison BP versus new experiment (325-340 nm); • Red– comparison BMD versus new experiment (325-345 nm); • Black– comparison BP versus BMD HARMONICS Final Meeting - ESRIN, Frascati

32. Comparison in Huggins band region: new data versus high resolution datasets, relative difference and shifts HARMONICS Final Meeting - ESRIN, Frascati

33. Comparison in DOAS region: new data versus SCIAMACHY (old and revised) • Data convolved with Gaussian slit function • Disagreement ~ 1 – 5 % for 241K, 273K and 293K, increasing at lower temperatures. • Wavelength shift of -0.005 to 0.015 nm. • Deviation: within the 2% accuracy limits for 243K, 273K and 293K, increase up to 5% for 203K, 223K. HARMONICS Final Meeting - ESRIN, Frascati

34. Chappuis and Wulf bands HARMONICS Final Meeting - ESRIN, Frascati

35. Direct comparison in the ‘minimum’ HARMONICS Final Meeting - ESRIN, Frascati

36. Chappuis band SCIA FM revised GOME-2 FM3 revised HARMONICS Final Meeting - ESRIN, Frascati

37. Wulf Band HARMONICS Final Meeting - ESRIN, Frascati

38. Wulf Band SCIA FM revised HARMONICS Final Meeting - ESRIN, Frascati

39. Wulf Band Anderson, Mauersberger, Journal of geophysical research 100(D2), 3033-3048, 1995 • Weak absorption, measurements are very sensitive to the baseline and S/N, low accuracy and precision -> FTS upgrade is needed; • Temperature dependence in NIR; • Region is interesting for future missions (SAGEII and SAGE III) HARMONICS Final Meeting - ESRIN, Frascati

40. Advantages and limitations of the new dataset • High resolution: 0.02 nm@300 nm – 0.1 nm @ 1000 nm • 11 temperatures, down to 193K • Spectral coverage UV- vis – NIR for all temperatures • Accurate wavelength calibration, better than 0.001 nm • Absolute accuracy: • 2 – 3% in UV/ visible, • 30% for 350 – 450 and 900 – 1050 nm HARMONICS Final Meeting - ESRIN, Frascati

41. http://www.iup.uni-bremen.de/gruppen/molspec/databases/index.htmlhttp://www.iup.uni-bremen.de/gruppen/molspec/databases/index.html Current O3 datasets in use http:/ HARMONICS Final Meeting - ESRIN, Frascati

42. Current status HARMONICS Final Meeting - ESRIN, Frascati

43. Live after HARMONICS • CH4 line parameters investigation (winter 2011-2012) (ESA ADVANSE); • Lab upgrade: dual-channel FT spectrometer (summer 2012) (University of Bremen) ; • Possible new measurements (starting from autumn 2012) : • Ozone: NIR and 10 mkm – staff support needed; • SO2 for UV sensors (320 nm) – staff support needed. HARMONICS Final Meeting - ESRIN, Frascati

44. Special thanks to former IUP members: Peter Spietz and Juan Carlos Gomez-Martin Thank you for attention ! HARMONICS Final Meeting - ESRIN, Frascati