1. Accent-troposat 2 final workshop, 30 Sept. - 01 Oct. 2008, FMI Helsinki, Finland Atmospheric bromine monoxide retrieval from space and ground-based UV-visible observations Nicolas Theys, F. Hendrick, M. Van Roozendael Belgian Institute for Space Aeronomy (IASB-BIRA) Brussels Troposat-2

2. Acknowledgements to: BIRA-IASB Univ. of Bremen - I. De Smedt - A. Rozanov & colleagues - Q. Errera, S. Chabrillat, F. Daerden - B. Dils Univ. of Heidelberg NIWA - M. Dorf - P. Johnston - K. Pfeilsticker - K. Kreher Univ. of Cambridge - X. Yang

3. Scientific activites within the AT-2 project (TG1) 1. Development of techniques to retrieve BrO columns and profiles from ground-based observations: - Harestua (60°N,11°E) - Observatoire de Haute-Provence (OHP; 44°N, 6°E) - Reunion Island (21°S, 55°E) - Lauder (45°S, 170°E) 2. Satellite total BrO columns retrieval : scientific products - GOME - SCIAMACHY - (+GOME-2) 3. Retrieval of tropospheric BrO columns: GOME, (+GOME-2). 4. Modelisation of stratospheric BrO using BASCOE. 5. Comparison between satellites, ground-based, balloon and modelled BrO data sets.

4. Overview 1. Multi-year comparison of stratospheric BrO retrieved from SCIAMACHY limb and GB observations 2. Long-term trend of stratospheric BrO using GB observations 3. Development of a stratospheric BrO climatology using the BASCOE model – application to the retrieval of tropospheric BrO VCD from GOME-2 (preliminary results) 4. Volcanic BrO observed by GOME-2 during the Kasatochi eruption

5. Comparison of strato. BrO retrieved from SCIAMACHY limb and GB observations Harestua 60°N OHP 44°N Lauder 45°S Hendrick et al., submitted to ACPD  SCIAMACHY limb stratospheric BrO profiles retrieved at the IUP/ Univ. of Bremen (scientific product version 3.2)  15-27 km BrO partial columns (altitude with high sensitivity to BrO profile for both instruments)  Reasonable agreement: relative difference < 11% standard deviat. in the 13-19% range  A small seasonal dependence in the relative difference between both data sets is observed

6. Long-term trend of stratospheric BrO using GB observations Hendrick et al., GRL, 2008  Trend analysis including linear and seasonal components (polyharmonic functions).  Trend values at both stations agree whithin their combined error bars.  Indication that Montreal Protocol restrictions on brominated substances have now reached the stratosphere.

7. Development of a stratospheric BrO climatology using the BASCOE model Motivation : retrieval of tropospheric BrO columns from satellite nadir observations (GOME, SCIAMACHY, GOME-2) → need to correct for the BrO absorption in the stratosphere  the impact of the atmospheric dynamics and the photochemistry on the stratospheric BrO distribution is accounted for by making use of O 3 and stratospheric NO 2 columns simultaneously measured by the satellite instrument.  the parameterization is based on the BACOE 3D-CTM which has been fully optimized for bromine chemistry and budget, and validated through comparisons using ground- based, balloon and SCIAMACHY limb observations. 12-20 km BrO partial columns15-30 km BrO partial columns (zonal mean) Theys et al., ACPD, 2008

8. Application to the retrieval of tropospheric BrO VCD from GOME-2 preliminary results Tropospheric VCD Total VCD Stratospheric VCD September 2007 (sza<80° & CF<0.4) Tropospheric AMFs are calculated using BrO profiles from the pTOMCAT model

9. Volcanic BrO observed by GOME-2 Kasatochi volcano (Alaska, 52.17°N, 175.51°W) massive eruption of 7th August 2008 Initial condition: 1 kg of BrO in 10-12 km height layer - Strong indication of the direct injection of at least 25-35 tons of reactive bromine in the UT/LS! - Transport north-eastward by fast near-tropopause jet-winds paper in preparation - submission soon in GRL - Strong indication of the direct injection of at least 25-35 tons of reactive bromine in the UT/LS! - Transport north-eastward by fast near-tropopause jet-winds paper in preparation - submission soon in GRL