DOAS Instruments onboard the LPMA / DOAS Balloon Gondola

1. Validation of SCIAMACHY Level-1 and Level-2 Products by Balloon-Borne Differential Optical Absorption Spectroscopy (DOAS) Dorf M.1, A. Butz1, H. Bösch4, C. Camy-Peyret2, M. Chipperfield3, K. Gerilowski6, K. Grunow5, W. Gurlit6, L. Kritten1, S. Kühl1, S. Payan2, A. Rozanov6, C. von Savigny6, B. Simmes1, C. Sioris7, F. Weidner1 and K. Pfeilsticker1 (1) Institut für Umweltphysik (IUP), Universityof 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. DOAS Instruments onboard the LPMA / DOAS Balloon Gondola LPMA: Limb Profile Monitor of the Atmosphere (FT-IR instrument) DOAS: Differential Optical Absorption Spectroscopy • ‘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 -5o) observations • Total mass 5 kg • Total power consumption ~5 W • Target species: O3, O4, NO2, BrO,nadir and limb radiance, possibly OClO, mini-DOAS can be operated on different balloon platforms

3. LPMA / DOAS Oberservation Mode Balloon ascent Solar occultation

4. SCIAMACHY Observation Mode • Sun synchronous low Earth orbit • Overpass around 10:30 LT • Vertical resolution of limb scan ~ 3.3 km • Global coverage every 3 days

5. Validation of SCIAMACHY Limb Profiles Comparison of SCIAMACHY and DOAS viewing geometry SLIMCAT 3D-CTM [M. Chipperfield] Diurnal variation of e.g. BrO and NO2, and spatial and temporal mismatch prevent direct comparison Photochemical modelling is necessary !

6. Validation of SCIAMACHY Limb Profiles – Meteorological Forcasting / Analysis 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 Plots courtesy of Katja Grunow (FU-Berlin)

7. Validation Strategy • Conduct balloon flights for as many different geophysical condition as possible • Calculate matches of collocated ENVISAT / SCIAMACHY overpasses • Retrieve SCIAMACHY Limb profiles for the corresponding overpasses • Calculate photochemical corrections for the balloon observation on calculated air mass trajectories •  Finally: Compare profiles !

8. LPMA / DOAS / mini-DOAS Balloon Flights Performed for the Validation of EnviSat / SCIAMACHY

9. Validation of Level 1 Products – The Solar Irradiance Spectrum Irradiance spectra referenced to Modtran 3.7 (updated Kurucz spectrum - Fontenla et al. 1999) • 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% Absolute calibration performed by IUP – Bremen

10. 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. Validation of Level 2 Products – BrOProfiles

12. Validation of Level 2 Products – BrOProfiles

13. Validation of Level 2 Products – BrOProfiles

14. Validation of Level 2 Products – BrOProfiles Janis Pukite (Heidelberg) Tues.: 11.30am Alexei Rosanov (Bremen) Tues.: 10am

15. Validation of Level 2 Products – O3 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. Validation of Level 2 Products – O3 Profiles ± 20% agreement in the 20 to 30 km range

17. Validation of Level 2 Products – NO2 Profiles • Underestimation below 20 km • Disrecpancies of the different retrievals below 20 km

18. Validation of Level 2 Products – NO2 Profiles ± 20% agreement in the 20 to 30 km range

19. Validation of Level 2 Products – mini-DOAS Limb Scanning Mode mini-DOAS deployed on: MIPAS – B2 and LPMA / IASI

20. Validation of Level 2 Products – miniDOAS Limb Scanning Mode Direct satellite match is possible!

21. Summary and Conclusions 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, NO2 and O3) inferred from IUP-Heidelberg, IUP-Bremen and Harvard-Smithsonian • In gerneral comparisons indicate an accuracy of: ± 20 % for O3 and NO2 • 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 O3, NO2, 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

22. Publications so far • 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