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Retrieval of BrO vertical distributions from SCIAMACHY limb measurements: Data quality assessment and algorithm improvements

Alexei Rozanov(1), John P. Burrows(1), Sven Kuehl(2), Chris McLinden(3), Klaus Pfeilsticker(2), Ross Salawitch(4), Bjoern-Martin Sinnhuber(1), Chris Sioris(5), Thomas Wagner(2) and Janis Pukite(2)

(1) University of Bremen, Otto-Hahn-Alle 1, D-28359 Bremen, Germany
(2) University of Heidelberg, Im Neuenheimer Feld 229 , D-69120 Heidelberg, Germany
(3) Environment Canada, 4905 Dufferin Street, ON M3H 5T4, Toronto, Canada
(4) Jet Propulsion Laboratory, 4800 East Oak Grove Drive, 91109, Pasadena, California, United States
(5) Harvard-Smithsonian Center for Astrophysics, Garden Street, mailstop 50, 02138, Cambridge, MA, United States

Abstract

In the recent years the efforts of several scientific groups were dedicated to an investigation of the BrO amount in the stratosphere aimed to answer a question whether the bromine loading is consistent with the current understanding of the stratospheric bromine chemistry. A special attention is payed to the lower stratosphere and upper troposphere regions were indications of significant disagreement between predicted and measured BrO amounts were found. To solve important problems arising with respect to the short lived bromine compounds in the lower stratosphere reliable observations of the BrO vertical distribution on the global scale are required.

At present, vertically resolved global measurements of stratospheric bromine can only be performed by the SCIAMACHY instrument which was launched on board the European Environment Satellite (ENVISAT-1) in March 2002 in a sun-synchronous orbit with an equator crossing local time of about 10 AM and 10 PM. The SCIAMACHY instrument measures the scattered and reflected solar radiation in limb and nadir geometry in the spectral range from 240 to 2380 nm and achieve the global coverage in 6 days.

Due to a complexity of the radiative transfer when measuring in the limb viewing geometry, sophisticated models and retrieval algorithms are required which could be sensitive to various input parameters. Additionally, the retrieval problem is complicated by a weak absorption of BrO. As recent comparisons show, this leads to a considerable disagreement between BrO profiles retrieved by different groups with respect to each other as well as with respect to balloon-born measurements. Furthermore, a strong scattering in the retrieved profiles is observed which is probably caused by the measurement noise.

This contribution is aimed to present first results of the joint project on the investigation of the retrieval quality of BrO vertical distributions from the SCIAMACHY limb measurements. The objectives of the project include an extended intercomparison of the retrieval results of different groups and a detailed discussion of the technical details with an aim to find origins of the disagreement and improve the existing algorithms.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry