the effect of stratospheric sulfur from pinatubo on the ... filethe effect of stratospheric sulfur...
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The effect of stratospheric sulfur from Pinatubo on the oxidizing capacity of the troposphere
Narcisa Bândă
Maarten Krol
Thomas Röckmann
Twan van Noije
Michiel van Weele
Jason Williams
10 May 2011
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http://www.esrl.noaa.gov/
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OH
Source – ozone photolysis ( O3 + hv 2OH )
Sink – reaction with CH4, CO, NMHCs, etc
+ H2O
CH4
Source – Emissions (natural, anthropogenic)
Sink – reaction with OH
( NO2+ hv NO + O3 ) + O2
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SO2 aerosol
SW UV
Decrease in photolysis
stratosphere
troposphere
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OH
Source – ozone photolysis ( O3 + hv 2OH )
Sink – reaction with CH4, CO, NMHCs, etc
+ H2O
CH4
Source – Emissions (natural, anthropogenic)
Sink – reaction with OH
( NO2+ hv NO + O3 ) + O2
JO3
JNO2
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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
• Emissions from EDGAR 4.2/4.1, RETRO fires, natural emissions from MACC and LPJ
• Methane nudged up to 550 hPa with observations from background stations (for now)
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Model setup
• 18.5 Tg SO2 emitted in the grid-cell containing Pinatubo on 15th June 1991 between 17-21 km, 20-24 km, 23-27 km
• The effect on photolysis in the period June-December 1991: • no Pinatubo • with Pinatubo, without SO2 absorption • with Pinatubo, with SO2 absorption
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SO2 plume validation
TOMS Injection 17-21 km
Injection 20-24 km Injection 23-27 km
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SO2 plume validation
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Sulphate aerosols
mid mid
high
low
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Sulphate aerosols
mid mid
high
low
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Aerosol size (14-20 N)
SAGE II
TM5
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Effect on photolysis rates and OH at the surface
SO2 absorption
on 22 June 1991 Aerosol scattering on 1 December 1991
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Effect on photolysis rates and OH at the surface
Aerosol scattering
SO2 absorption
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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
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Tropospheric CH4 sink
Total: 0.9 Tg
Total: 6.7 Tg
Tg/year No Pin
Pin Aer
Pin Aer&SO2
Emissions 451 451 451
CH4+OH -502 -491 -490
Nudging surface
129 119 118
Nudging strat -25 -25 -25
Burden chng 51 53 53
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Note on vertical resolution 60 levels 34 levels
Average profile 20S-20N
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Note on vertical resolution
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Conclusions • The evolution of the SO2 and sulphate aerosols can be
modelled reasonably well • Difficult to match both plume height and horizontal
distributions, probably due to uncertainties in transport • 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 in TM5
• ‘Free running’ CH4
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Acknowledgements
Philippe le Sager
Joost Aan de Brugh (SRON)
Jeroen van Gent (BISA)
Ulrike Niemeyer (MPI-M)