1. Institut für Umweltphysik, University of Heidelberg, Germany Validation of SCIAMACHY Level-1 and Level-2 Products by Balloon-Borne Differential Optical Absorption Spectroscopy (DOAS) Dorf M. 1, A. Butz 1, H. Bösch 4, C. Camy-Peyret 2, M. Chipperfield 3, K. Gerilowski 6, K. Grunow 5, W. Gurlit 6, L. Kritten 1, S. Kühl 1, S. Payan 2, A. Rozanov 6, C. von Savigny 6, B. Simmes 1, C. Sioris 7, F. Weidner 1 and K. Pfeilsticker 1 (1) Institut für Umweltphysik (IUP), University of Heidelberg, Heidelberg, Germany (2) Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique (LPMAA), Université Pierre et Marie Curie, Paris, France (3) Institute for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK (4) Jet Propulsion Laboratory, Pasadena, United States (5) Meteorologisches Institut, Freie Universität Berlin, Berlin, Germany (6) Institut für Umweltphysik (IUP), University of Bremen, Bremen, Germany (7) Harvard-Smithsonian Center for Astrophysics, Cambridge, USA

2. Institut für Umweltphysik, University of Heidelberg, Germany ‘Big’- DOAS instrument (direct Sun): 2 grating spectrometers in one thermostated (273 K) and evacuated housing Cooled photo diode detectors (1024 diodes, T = - 260 K) Wavelength ranges and resolution: UV (316 - 418 nm, Δλ = 0.5 nm) Visible (400 - 653 nm, Δλ = 1.3 nm) Light intake: Solar tracker and glas fibre bundle Efficient spectrometer stray-light suppression Solar occultation Total mass 45 Kg Total power consumption ~20 W Target species: O3, O4, H2O, NO2, OClO, BrO, IO, OIO, and solar irradiance Mini-DOAS instruments (Nadir & Limb): 2 grating spectrometers in one thermostated (273 K) housing Cooled linear silicon CCD array (2048 pixels, T = 273 K) Wavelength range and resolution: (320 - 520 nm, Δλ = 0.8 nm) Light intake: Glass fibre bundles NADIR and LIMB (+1 to -5 o ) observations Total mass 5 kg Total power consumption ~5 W Target species: O3, O4, NO2, BrO, nadir and limb radiance, possibly OClO, DOAS Instruments onboard the LPMA / DOAS Balloon Gondola mini-DOAS can be operated on different balloon platforms LPMA: Limb Profile Monitor of the Atmosphere (FT-IR instrument) DOAS: Differential Optical Absorption Spectroscopy

3. Institut für Umweltphysik, University of Heidelberg, Germany Balloon ascentSolar occultation LPMA / DOAS Oberservation Mode

4. Institut für Umweltphysik, University of Heidelberg, Germany Sun synchronous low Earth orbit Overpass around 10:30 LT Vertical resolution of limb scan ~ 3.3 km Global coverage every 3 days SCIAMACHY Observation Mode

5. Institut für Umweltphysik, University of Heidelberg, Germany Validation of SCIAMACHY Limb Profiles Comparison of SCIAMACHY and DOAS viewing geometry Diurnal variation of e.g. BrO and NO 2, and spatial and temporal mismatch prevent direct comparison  Photochemical modelling is necessary ! SLIMCAT 3D-CTM [M. Chipperfield]

6. Institut für Umweltphysik, University of Heidelberg, Germany Validation of SCIAMACHY Limb Profiles – Meteorological Forcasting / Analysis Plots courtesy of Katja Grunow (FU-Berlin) Air mass trajectory calculations for the LPMA / DOAS flight at Air sur l`Adour (France) Oct. 09, 2003 Find best coincidences satellite and balloon observ. Powerfull tool for flight planning Necessary to calculate photochemical changes

7. Institut für Umweltphysik, University of Heidelberg, Germany Validation Strategy 1.Conduct balloon flights for as many different geophysical condition as possible 2.Calculate matches of collocated ENVISAT / SCIAMACHY overpasses 3.Retrieve SCIAMACHY Limb profiles for the corresponding overpasses 4.Calculate photochemical corrections for the balloon observation on calculated air mass trajectories  Finally: Compare profiles !

8. Institut für Umweltphysik, University of Heidelberg, Germany LPMA / DOAS / mini-DOAS Balloon Flights Performed for the Validation of EnviSat / SCIAMACHY

9. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 1 Products – The Solar Irradiance Spectrum Absolute calibration performed by IUP – Bremen Previous ESA SCIAMACHY calibration 15% larger Significantly improved by using IUP-Bremen re-calibration Agreement of SCIAMACHY: (415–585)nm - 0.4% (370–415)nm - 1.6% (325–370)nm - 5.7% Irradiance spectra referenced to Modtran 3.7 (updated Kurucz spectrum - Fontenla et al. 1999)

10. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 1 Products – Radiative Transfer Models Limb radiances measured by mini-DOAS: azimuth of 90° and elevation of +0.5° during balloon ascent Comparison with RT modelling using: TRACY : IUP – Heidelberg SCIATRAN : IUP – Bremen

11. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – BrO Profiles

12. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – BrO Profiles

13. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – BrO Profiles

14. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – BrO Profiles Alexei Rosanov (Bremen) Tues.: 10am Janis Pukite (Heidelberg) Tues.: 11.30am

15. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – O 3 Profiles Systematic underestimation at 24 to 28 km: Still tangent height error? Underestimation below 20 km: Lower sensitivity of satellite Unaccounted horizontal trace gas variations

16. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – O 3 Profiles ± 20% agreement in the 20 to 30 km range

17. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – NO 2 Profiles Underestimation below 20 km Disrecpancies of the different retrievals below 20 km

18. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – NO 2 Profiles ± 20% agreement in the 20 to 30 km range

19. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – mini-DOAS Limb Scanning Mode mini-DOAS deployed on: MIPAS – B2 and LPMA / IASI

20. Institut für Umweltphysik, University of Heidelberg, Germany Validation of Level 2 Products – miniDOAS Limb Scanning Mode Direct satellite match is possible!

21. Institut für Umweltphysik, University of Heidelberg, Germany Results of the so far 5 validation flights: Overall reasonable agreement fot level 1 products (solar irradiance and limb radiance) of < ± 5 %, with updated SCIAMACHY irradiance calibration Variable good agreement is obtained for level 2 (not yet operational) products (BrO, NO 2 and O 3 ) inferred from IUP-Heidelberg, IUP-Bremen and Harvard-Smithsonian In gerneral comparisons indicate an accuracy of: ± 20 % for O 3 and NO 2 For BrO a bias of – 20 % / + 20 % is observed for above / below 25 km (Harvard – Smithsonian retrieval only) Air mass trajectory calculations prove to be a powerful tool for satellite validation – for flight planning and for calculation of photochemical change Upcoming activities: Validation of level 2 products OCLO (at high-latitudes) and O 3, NO 2, BrO, IO... (at low-latitudes) Validation of complementary data products from EnviSat - MIPAS and GOMOS Results are also of value for existing satellite measurements, e.g. OMI, or future validation activities, e.g. GOME – 2 Summary and Conclusions

22. Institut für Umweltphysik, University of Heidelberg, Germany Butz, A., H. Bösch, C. Camy-Peyret, M. Chipperfield, M. Dorf, G. Dufour, K. Grunow, P. Jeseck, S. Kühl, S. Payan, I. Pepin, J. Pukite, A. Rozanov, C. von Savigny, C. Sioris, F. Weidner, K. Pfeilsticker, Inter-comparison of stratospheric O3 and NO2 abundances retrieved from balloon-borne direct sun observations and Envisat/SCIAMACHY limb measurements, Atmos. Chem. Phys., 6, 1293 -1314, 2006. Dorf, M., H. Bösch, A. Butz, C. Camy-Peyret, M. P. Chipperfield, A. Engel, F. Goutail, K. Grunow, F. Hendrick, S. Hrechanyy, B. Naujokat, J.-P. Pommereau, M. Van Roozendael, C. Sioris, F. Stroh, F. Weidner, and K. Pfeilsticker, Balloon-borne stratospheric BrO measurements: Comparison with Envisat / SCIAMACHY BrO limb profiles, ACP (revised) 2006. Gurlit, W., H. Bösch, H. Bovensmann, J. P. Burrows, A. Butz, C. Camy-Peyret, M. Dorf, K. Gerilowski, A. Lindner, S. Noel, U. Platt, F. Weidner, and K. Pfeilsticker, The UV-A and visible solar irradiance spectrum: Inter-comparison of absolutely calibrated, spectrally medium resolved solar irradiance spectra from balloon-, and satellite-borne measurements, Atmos. Chem. Phys., 5, 1879–1890, 2005. Weidner, F., H. Bösch, H. Bovensmann, J. P. Burrows, A. Butz, C. Camy-Peyret, M. Dorf, K. Gerilowski, W. Gurlit, U. Platt, C. von Friedeburg, T. Wagner, and K. Pfeilsticker, Balloon-borne Limb profiling of UV/vis skylight radiances, O3, NO2, and BrO: Technical set-up and validation of the method, Atmos. Chem. Phys., 5, 1409–1422, 2005. And various Ph.D. and Master theses Publications so far