1. 1 SO 2 Air Mass Factors for pollution and volcanic emissions OMI Science Team Meeting De Bilt, 20 - 22 June 2006 Pieter Valks, Werner Thomas, Thilo Ebertseder, Jos van Geffen

2. 2 Outline SO 2 Air Mass Factors for anthropogenic pollution tropospheric SO 2 profile climatology from EURAD model AMF calculations with LIDORT SO 2 Air Mass Factors for volcanic emissions analyses for Mt. Etna eruptions in 2001/2002 Report on ongoing work at DLR and BIRA-IASB on SO 2 retrieval for SCIAMACHY and GOME-2 framework: GSE-PROMOTE and EUMETSAT-OzoneSAF

3. 3 The EURAD Air Quality model EURopean Air Pollution Dispersion (EURAD) model system Developed by RIU institute of the University of Cologne EURAD/RIU system is run operationally at DLR Neustrelitz Jacobs et al., J. Appl. Meteor., Vol. 34, 1995

4. 4 EURAD: model setup

5. 5 EURAD: model region Spatial resolution: ~ 125 km 23 vertical layers up to 100 hPa

6. 6 EURAD SO 2 profile climatology One year of EURAD SO 2 data: July 2005 – June 2006 use data over land surface Average SO 2 profile for 4 regimes: background SO 2 (< 0.3 DU) weak SO 2 pollution (0.3 – 0.6 DU) moderate SO 2 pollution (0.6 – 1 DU) strong SO 2 pollution ( > 1 DU) Profile climatology for each season

7. 7 EURAD tropospheric SO 2 columns January 2006

8. 8 EURAD tropospheric SO 2 columns August 2005

9. 9 EURAD SO 2 profile climatology Summer

10. 10 EURAD SO 2 profile climatology Spring

11. 11 SO 2 Air Mass Factor calculations LIDORT V2.2+ radiative transfer model spherical-shell treatment for wide off-nadir viewing use ´classical AMF definition´: A = ln (I/I o ) /  AMF wavelength: 320 nm appropriate for DOAS fitting-window: 315-326 nm based on closed-loop test using synthetic data (Thomas et al.) AMF look-up table 4 tropospheric SO 2 profiles (for each season) 3 ozone profiles: 225, 350, 525 DU surface pressure and albedo geometry parameters: SZA, VZA, RAA aerosol-free atmosphere SO 2 profile selection could be based on slant column and location

12. 12 Air Mass Factors for EURAD SO 2 profiles nadir viewing clear-sky A s = 0.05 Summer

13. 13 Air Mass Factors for EURAD SO 2 profiles nadir viewing clear-sky A s = 0.05 Winter

14. 14 Air Mass Factors for volcanic profiles nadir viewing clear-sky A s = 0.05 plume vertical thickness  2 km SO 2 col. = 3 DU

15. 15 Air Mass Factors for volcanic profiles nadir viewing clear-sky A s = 0.05 plume vertical thickness  2 km SO 2 col. = 30 DU

16. 16 nadir viewing clear-sky A s = 0.05 sza = 45  Thomas et al., J. Atm. Chem., 2005 Volcanic AMFs with aerosol loading

17. 17 Trajectory analyses for Mt. Etna eruptions Mt. Etna is the most active volcano in Europe Trajectory analyses to determine plume height ~ 4 km in Summer 2001 => AMF ~ 1.5 ~ 5 km in Fall 2002 => AMF ~ 1.9 uncertainty in plume height: ~ 1 km Assume maritime aerosol model, aer. opt.: 0.3 aerosols large error source close to the volcano Trajectory analyses not suitable for operational processing => plume height selection based on volcano type ?

18. 18 Vertical column calculations   E )1( cloudclear cloud AA A V      ´classical´ total column formulation: E: Slant Column A: Air Mass Factor V : Vertical Column  : intensity-weighted Cloud Fraction Clouds are treated in the independent pixel approximation