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The effect of stratospheric sulfur from Pinatubo on the oxidizing capacity of the troposphere

The effect of stratospheric sulfur from Pinatubo on the oxidizing capacity of the troposphere. Narcisa Bândă. 10 May 2011. http://www.esrl.noaa.gov/. OH - the tropospheric oxidant. + H 2 O. Source – ozone photolysis ( O 3 + hv 2OH ). OH. + O 2.

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The effect of stratospheric sulfur from Pinatubo on the oxidizing capacity of the troposphere

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  1. The effect of stratospheric sulfur from Pinatubo on the oxidizing capacity of the troposphere Narcisa Bândă 10 May 2011

  2. http://www.esrl.noaa.gov/

  3. OH - the tropospheric oxidant + H2O Source – ozone photolysis ( O3 + hv 2OH ) OH + O2 ( NO2+ hv NO + O3) Sink – reaction with CH4, CO, NMHCs, etc Source – Emissions (natural, anthropogenic) CH4 Sink – reaction with OH

  4. UV SW SO2 Decrease in photolysis stratosphere aerosol troposphere

  5. OH - the tropospheric oxidant + H2O JO3 Source – ozone photolysis ( O3 + hv 2OH ) OH + O2 JNO2 ( NO2+ hv NO + O3) Sink – reaction with CH4, CO, NMHCs, etc Source – Emissions (natural, anthropogenic) CH4 Sink – reaction with OH

  6. Model setup TM5 global chemistry model 3x2, 60 levels ECMWF ERA-Interim meteorology fields Aerosol module M7 coupled to photolysis M7 setup as recommended in Kokkola et al. 2009: • no soluble coarse mode, accumulation mode σ=1.2 instead of 1.59 • no tropospheric aerosols 18.5 Tg SO2 emitted in the grid-cell containing Pinatubo on 15th June 1991 between 20-24 km The effect on photolysis in the period June-December 1991: • no Pinatubo • with Pinatubo, without SO2 absorption • with Pinatubo, with SO2 absorption

  7. SO2 plume evolution TOMS http://so2.gsfc.nasa.gov/ SO2 lifetime: 36 days (MLS: 33 days, TOMS: 25 days) Injection 20-24 km Injection 23-27 km

  8. Sulphate aerosols Aerosol size (14-20 N) TM5 SAGE II

  9. Effect on photolysis rates and OH at the surface SO2 absorption on 22 June 1991 Aerosol scattering on 1 December 1991

  10. Effect on photolysis rates and OH at the surface Aerosol scattering SO2 absorption

  11. Effect on photolysis rates and OH Average profile change 30S-30N due to aerosol scattering and SO2+OH Average profile change 0-30N due to SO2 absorption SO2+OH

  12. Tropospheric CH4 sink Total: 0.9 Tg Total: 6.7 Tg

  13. Conclusions The evolution of the SO2 and sulphate aerosols can be modelled reasonably well The effect on global OH is less than 1% for SO2 and 3% for aerosols, with larger effects regionally This results in decreases in the CH4 sink of 1 Tg and 7 Tg respectively in the first 6 months after the eruption Future work: • Improve plume evolution (injection height) • Look at a 2-year period • Study the effects of stratospheric ozone depletion, climate change after Pinatubo on OH, CH4 (see Banda et al. ACP 2013) • TM5 + EC-Earth

  14. OH - the tropospheric oxidant + H2O JO3 Source – ozone photolysis ( O3 + hv 2OH ) OH + O2 JNO2 ( NO2+ hv NO + O3) Sink – reaction with CH4, CO, NMHCs, etc Source – Emissions (natural, anthropogenic) CH4 Sink – reaction with OH

  15. Acknowledgements Philippe le Sager (KNMI) Jason Williams (KNMI) Joost Aan de Brugh (SRON) Jeroen van Gent (BISA) Ulrike Niemeyer (MPI-M) NWO SSiRC

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