The Sensitivity of Global Nucleation, CCN and Climate to SO2 and Criegee-Intermediate Chemistry Jeff Pierce, Mat Evans, Cat Scott, Steve D'Andrea, Delphine Farmer, Erik Swietlicki and Dom Spracklen Pierce, J. R., Evans, M. J., Scott, C. E., D'Andrea, S. D., Farmer, D. K., Swietlicki, E., and Spracklen, D. V.: Weak sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO2 chemistry, Atmos. Chem. Phys., 13, 3163-3176, doi:10.5194/acp-13-3163-2013, 2013.
SO2 fates H2O2, O3 SO2 OH SO42~25%: aqueous oxidation ~15%: gas-phase oxidation H2SO4 ~60%: deposition
SO2 fates H2O2, O3 SO2 OH SO42~25%: aqueous oxidation ~15%: gas-phase oxidation This path is necessary for H2SO4 nucleation and growth ~60%: deposition
SO2 fates SO2 H2O2, O3 OH, X SO42~25%: aqueous oxidation ~??%: gas-phase oxidation H2SO4 ~60%: deposition
Aerosol size distribution Particle Number Accumulation mode Ultrafine (Aitken) mode ~100 nm - Cloud Condensation Nuclei (CCN) - Aerosol scattering/absorption Cloud processing Nucleation Coagulation Aqueous chem Collection Condensation >1 μm ~1 nm Particle Size Deposition Primary Emissions Primary Emissions Deposition
Criegee from alkenes Initial steps of ozonolalysis of an alkene Criegee intermediate Criegee intermediate http://www.organic-chemistry.org/namedreactions/ozonolysis-criegee-mechanism.shtm
SO2 oxidation by the Criegee intermediate + SO2 SO3 SO3 + H2O H2SO4 Welz et al. Direct Kinetic Measurements of Criegee Intermediate (CH2OO) Formed by Reaction of CH2I with O2, Science, 2012. - SO2 + Criegee reaction is faster than previously thought! Mauldin et al., A new atmospherically relevant oxidant of sulphur dioxide, Nature, 2012. - SO2 + Criegee is important for producing a large fraction of H 2SO4 in the forested boundary layer!
SO2 oxidation by the Criegee intermediate + SO2 SO3 Add this mechanism to GEOS-Chem SO3 + H2O H2SO4 w/ aerosol microphysics Welz et al. Direct Kinetic Measurements of Criegee Intermediate (CH OO) Formed by Reaction of CH2I with O2, Science, 2012. - SO2 + Criegee reaction is faster than previously thought! 2 Mauldin et al., A new atmospherically relevant oxidant of sulphur dioxide, Nature, 2012. - SO2 + Criegee is important for producing a large fraction of H 2SO4 in the forested boundary layer!
GEOS-Chem-TOMAS 3D atmospheric model: GEOS-Chem Chemical Transport Model 47 vertical layers Online chemistry Aerosol microphysics: TwO-Moment Aerosol Sectional (TOMAS) 4x5 horizontal resolution 40 size sections: 1 nm 10 μm Condensation, coagulation, nucleation Species: Sulfate, sea-salt, EC, OC, Dust
GEOS-Chem-TOMAS 3D atmospheric model: GEOS-Chem Chemical Transport Model 4x5 horizontal resolution 47 vertical layers Online chemistry Aerosol microphysics: TwO-Moment Aerosol Sectional (TOMAS) Add Criegee formation from: 40 size sections: 1 nm 10 μm Isoprene Condensation, coagulation, Methacroleinnucleation Species: Sulfate, sea-salt, EC, OC, Dust Methyl vinyl ketone Monoterpenes Propene
GEOS-Chem Global SO2-loss pathways Without Criegee chemistry With Criegee chemistry
Boundary-layer increases in H2SO4 vapor from addition of CI+SO2 July mean Annual mean July mean
BL Increase in total aerosol and CCN number from addition of CI+SO2 Dp > 10 nm Annual mean Dp > 10 nm July mean ~ CCN Dp > 80 nm Annual mean ~ CCN Dp > 80 nm July mean
BL Increase in total aerosol and CCN number from addition of CI+SO2 More H2SO4 Faster growth Dp > 10 nm Annual mean Dp > 10 nm But! ~ CCN Dp > 80 nm Annual mean July mean Increased total particle surface area Slower growth More coagulation Dp > 80 nm July mean Small CCN change!
Cloud albedo effect from adding CI+SO2 chemistry Global mean = 0.03 W m-2
Criegee summary Criegee intermediate may be important oxidant of SO2 near alkene sources Could increase H2SO4 vapor formation by ~5% globally and over 400% regionally CCN and indirect forcing changes weak due to microphysical dampening
Extra slides
Comparison to measurements
For a 15% increase in SO2+OH Change in CN80 (concentration of particles with Dp > 80 nm) % %
Aerosol size distribution Particle Number Accumulation mode Ultrafine (Aitken) mode ~100 nm - Cloud Condensation Nuclei (CCN) - Aerosol scattering/absorption Cloud processing Nucleation Coagulation Condensation >1 μm ~1 nm Particle Size Deposition Primary Emissions Primary Emissions Deposition
Aerosol size distribution Particle Number Accumulation mode Ultrafine (Aitken) mode ~100 nm - Cloud Condensation Nuclei (CCN) - Aerosol scattering/absorption Cloud processing Nucleation Coagulation Condensation >1 μm ~1 nm Particle Size Deposition Primary Emissions Primary Emissions Deposition
Aerosol size distribution Particle Number Accumulation mode Ultrafine (Aitken) mode ~100 nm - Cloud Condensation Nuclei (CCN) - Aerosol scattering/absorption Cloud processing Nucleation Coagulation Condensation >1 μm ~1 nm Particle Size Deposition Primary Emissions Primary Emissions Deposition
Not every new particles becomes a CCN! Vehkamäki and Riipinen, 2012
Organic submicron mass in the continental boundary layer Jimenez et al., 2009
Uncertainty of SOA in models How much do condensing organics contribute to the growth of ultrafine particles? How sensitive are modeled CCN and size distributions to the amount of SOA? Can these be optimized?
OH does not generate enough H2SO4 in forested region Mauldin et al., A new atmospherically relevant oxidant of sulphur dioxide, Nature, 2012
X related to VOCs from trees? Mauldin et al., A new atmospherically relevant oxidant of sulphur dioxide, Nature, 2012
Spatial features
Increases in H2SO4 vapor from addition of CI+SO2 Annual mean Annual mean July mean July mean