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. 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), 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

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 -5o) 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

Institut für Umweltphysik, University of Heidelberg, Germany

Balloon ascent Solar occultation

LPMA / DOAS Oberservation Mode

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

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 NO2, and spatial and temporal mismatch prevent direct comparison Photochemical modelling is necessary !

SLIMCAT 3D-CTM [M. Chipperfield]

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

Institut für Umweltphysik, University of Heidelberg, Germany

Validation Strategy

1. Conduct balloon flights for as many different geophysical condition as possible2. Calculate matches of collocated ENVISAT / SCIAMACHY overpasses 3. Retrieve SCIAMACHY Limb profiles for the corresponding overpasses4. Calculate photochemical corrections for the balloon observation on calculated air

mass trajectories Finally: Compare profiles !

Institut für Umweltphysik, University of Heidelberg, Germany

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

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)

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

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – BrO Profiles

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – BrO Profiles

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – BrO Profiles

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

Institut für Umweltphysik, University of Heidelberg, Germany

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

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – O3 Profiles

± 20% agreement in the 20 to 30 km range

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – NO2 Profiles

•Underestimation below 20 km

•Disrecpancies of the different retrievals below 20 km

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – NO2 Profiles

± 20% agreement in the 20 to 30 km range

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

Institut für Umweltphysik, University of Heidelberg, Germany

Validation of Level 2 Products – miniDOAS Limb Scanning Mode

Direct satellite match is possible!

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, 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

Summary and Conclusions

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