1. Harmonizationof GOME, SCIAMACHY, GOME-2 ozone cross-sections Anna Serdyuchenko, John P. Burrows, Mark Weber, Wissam Chehade University of Bremen, Germany Institute of Environmental Physics 64th International Symposium on Molecular spectroscopy Columbus, OH USA, June 22-26, 2009

2. University of Bremen, IUP, Molecular Spectroscopy Lab 2 Atmospheric species detection:  Available spectrometers  Time and space coverage Available databases for the reference data:  Laboratory measurements;  Satellite spectrometers measurements;  Comparison of datasets. Challenges of cross-section measurements in lab  Modern demands on the O3 absorption cross- section quality

3. University of Bremen, IUP, Molecular Spectroscopy Lab3 Long-term measurements of O3 (and NO2) are important for air quality study, Montreal Protocol monitoring of ozone depleting substances, climatology etc Long-term global data sets covering several decades are only available by combining datasets from multiple sensors:  GOME, GOME2: Global Ozone Monitoring Experiment  SCIAMACHY: Scanning Imaging Absorption Spectrometer for Atmospheric Chartography  TOMS: Total Ozone Mapping Spectrometer  OMI: Ozone Monitoring Instrument  Ground based instruments: Brewer, Dobson spectrophotometers Monitoring:  Troposphere: biomass burning, pollution, arctic haze, forest fires, dust storms, industrial plumes  Stratosphere: ozone chemistry, volcanic events, solar proton events  Clouds, aerosols, UV index

4. University of Bremen, IUP, Molecular Spectroscopy Lab4  Satellite spectrometers measure the solar radiation transmitted, backscattered and reflected from the Earth atmosphere and surface, also direct sun light  Absorption spectra cover: O3 O2 NO2 N2O BrO OClO SO2 H2CO2 CO CO2 CH4 H2O  GOME, GOME2 (Global Ozone Monitoring Experiment): scanning 4 channels grating spectrometer with nadir-view  SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography): scanning 8 channels grating spectrometer with nadir/limb-view

5. University of Bremen, IUP, Molecular Spectroscopy Lab5 GOME / GOME2: Global Ozone Monitoring Experiment SCIAMACHY: Scanning Imaging Absorption Spectrometer for Atmospheric Chartography MetOP: is a series of three satellites to be launched sequentially (2006, 2010, 2020) At least two decades of observations with global coverage SpectrometerSatelliteLaunchedSpatial resolution, km GOMEERS-2April 199540 x 40 to 40 x 320 SCIAMACHYENVISATMarch 2002Limb: 3 x 132 Nadir: 32 x 215 GOME2MetOp -AOctober 200640 x 80 to 40 x 240 MetOp - BJune 2010 (plan)

6.  Spurious instrumental trends in multiple instrument time series  GOME: no trend  SCIAMACHY: -0.4%/year State of the Climate in 2008, Bull. Amer. Meteor. Soc., submitted, 2009 Cross-section used: GOME: Burrows et al. 1999 SCIAMACHY: Bogumil et al. 2003 (scaled) SBUV/TOMS/OMI: Bass & Paur 1985

7.  GOME/SCIAMACHY retrieval uses DOAS (differential spectral fitting) in 325-335 nm window  Dobson standard retrieval : AD pairs and CD pairs (similarly for TOMS)  A-pair: 305.5/325.4 nm  C-pair: 311.5/332.4 nm  D-pair: 317.6/339.8 nm ◦ Brewer standard retrieval uses Brewer wavelength ratio pairs formed from B0 to B4

8. University of Bremen, IUP, Molecular Spectroscopy Lab8 Instrumental Slit Function Instrumental Slit Function Convolution  Convolution  O3 Spectrum cross-sections measured with the satellite instrument cross-sections measured with the satellite instrument O3 Spectrum Data Retrieval and Analysis Determination of O3 Columns in the Atmosphere Determination of O3 Columns in the Atmosphere laboratory measurements of high resolution cross-section spectra laboratory measurements of high resolution cross-section spectra

9. University of Bremen, IUP, Molecular Spectroscopy Lab9 laboratory measurements of high resolution cross-section spectra laboratory measurements of high resolution cross-section spectra Instrumental Slit Function Instrumental Slit Function Convolution  Convolution  O3 Spectrum Data Retrieval and Analysis Determination of O3 Columns in the Atmosphere Determination of O3 Columns in the Atmosphere cross-sections measured with the satellite instrument cross-sections measured with the satellite instrument O3 Spectrum

10. University of Bremen, IUP, Molecular Spectroscopy Lab10

11. University of Bremen, IUP, Molecular Spectroscopy Lab11 HITRAN 2008

12. University of Bremen, IUP, Molecular Spectroscopy Lab12 For GOME, SCIAMACHY, and GOME2 flight models were used to measure absorption cross-section prior to launch: experimental set-up Calibration Apparatus for Trace Gas Absorption Spectroscopy (CATGAS); Slightly different resolution 0.17 -0.3 nm Advantage: exact match of spectral resolution between satellite radiance and cross-sections Knowledge for instrumental slit function is not needed

13. University of Bremen, IUP, Molecular Spectroscopy Lab13 I - transmitted intensity I 0 - initial intensity - wave length OD - optical density Red – absorption/baseline, Blue – lamp monitoring UV/VIS : Xe, D2 Lamp Calibration: HgCd lamp Detector: LN2 cooled chip Cell:120 cm long, 5 cm Dia thermostated evacuated

14. University of Bremen, IUP, Molecular Spectroscopy Lab14 Data setTemperatures, K Resolution, nm: Wavelength covered, nm GOME FM Burrows et al., 1999 ‏ 202 221 241 273 2930.17 @ 330 nm230 - 800 SCIAMACHY FM Bogumil et al., 2003 203 223 243 273 2930.20 @ 330 nm230 - 2380 GOME2 FM Spietz et al., 2005 203 223 243 273 2930.29 @ 330nm240 – 790 Paur and Bass, 1985203 218 228 243 273 298 <0.025 nm(?) ‏ 245 - 345 Malicet et al. 1995 Brion et al., 1993 Daumont et al., 1992 218 228 243 273 2950.01-0.02 nm 195-345 UV-FTS Voigt et al., 2001 203 223 246 280 293 0.03 @ 230 nm230 - 850

15. University of Bremen, IUP, Molecular Spectroscopy Lab15  cover broad spectral range (0.2-1.2 µm)  cover most atmospheric temperatures BUT all above 200 K  Comparison of results from different instruments:  adjustment of resolution is needed  Data quality check (temperature dependence)  Minimization of residuals by comparison of O3: wavelength shifts, scaling Cross-sectionsShift [nm] Scaling to Malicet, Brion, Daumont Scaling to GOME1 GOME FM+0.017(2)1.027(2)- SCIAMACHY FM+0.008(2)0.970(3)0.944 GOME2 FM3-0.047(2)0.950(7)0.925 -5% -8%

16. SCIAMACHY total O 3 retrieval (using SCIAMACHY reference spectra) are 5% higher than GOME (with GOME reference spectra) in the range 325-335 nm GOME2 total O 3 retrieval (using GOME2 reference spectra) is 8% higher than calculated with resolution adjusted GOME FM reference data Harmonisation of O 3 flight model cross-sections from GOME and SCIAMACHY for a consistent retrieval Two approaches: reanalysis of laboratory data from the CATGAS campaigns new laboratory measurements:  experience from the previous researchers of IUP: CATGAS GOME2 experimental set-up, Fourier Transform Spectrometer;  potential error sources analysis & modification of set-up and conditions set;  sufficient accuracy to detect a 1% pro decade trend University of Bremen, IUP, Molecular Spectroscopy Lab16

17.  The overwhelming need for atmospheric measurements in the UV-Vis is to obtain improved cross-sections of ozone using FTS measurements; particular care has to be paid to avoid baseline uncertainties which are a major source of systematic errors in such measurements.  Wavelength coverage of 240–1000 nm is required, at 0.01 nm spectral resolution or better.  Absolute intensities should be accurate to at least 2% through the Hartley–Huggins and Chappuis bands.  Vacuum wavelength accuracy: better than 0.001 nm, reflecting the accuracy to which atmospheric spectra can be calibrated using correlation with the Fraunhofer spectrum.  Measurements should be made over the 180–300 K temperature range. *J.Orphal, K.Chance.Ultraviolet and visible absorption cross-sections for HITRAN Journal of Quantitative Spectroscopy & Radiative Transfer 82 (2003) 491–504 17

18. About two decades of observation from satellites spectrometers will be possible Three satellite spectrometers were calibrated by Bremen researchers. Several sets of absorption cross-sections produced, which include slit-functions. Disagreement between retrieved data to be corrected. Reanalysis of the data obtained during measurements campaigns New measurements Work is supported by European Space Agency University of Bremen, IUP, Molecular Spectroscopy Lab18

19. University of Bremen, IUP, Molecular Spectroscopy Lab19 GOME2 FM3: At some temperatures deviation of 2% (223 K, 243K) h