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Sensitivity of sulfate direct climate forcing to the hysteresis of particle phase transitions

Sensitivity of sulfate direct climate forcing to the hysteresis of particle phase transitions. Jun Wang, Andrew Hoffman, Scot Martin, Daniel Jacob. Present at 3rd GEOS–Chem Users' Meeting, April. 11, 2007. Introduction of sulfate phase & composition. Extent of neutralization

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Sensitivity of sulfate direct climate forcing to the hysteresis of particle phase transitions

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  1. Sensitivity of sulfate direct climate forcing to the hysteresis of particle phase transitions Jun Wang, Andrew Hoffman, Scot Martin, Daniel Jacob Present at 3rd GEOS–Chem Users' Meeting, April. 11, 2007

  2. Introduction of sulfate phase & composition Extent of neutralization X= [NH4]/2[SO4] X = 1 X = 0.75 X = 0.5 0 X  1 Solids: AS (NH4)2SO4 LET (NH4)3H(SO4)2 AHS (NH4) HSO4 Aqueous: SO4aq SO42-, H+, NH4+, H2O deliquesce Phase transition Crystallization

  3. Aerosol direct forcing on climate? Aerosol phase transition To predict the phase transition requires: (a) Current phase (RH back-trajectory) which curve ? (b) RH in next time step which direction? (c) CRH(X) & DRH(X)Phase changes? The hysteresis of sulfate phase transition Crystalline relative humidity Deliquesce relative humidity aqueous solids

  4. DRH CRH Treatment of hysteresis effect in previous studies Limiting case studies F: 18%, Haywood et al., 1997 24%, Martin et al., 2004 Chung et al., 2003 All previous forcing estimates diagnose the sulfate phase based on local RH only. A full consideration of the hysteresis loop has not been made in the past estimate of sulfate climate forcing.

  5. Optical properties Wang & Martin (2007) Surface reflectance Koelemeijer et al. (2003) RTM (Fu & Liou, 1998) Approach GEOS-Chem CTM Park et al. (2003) Lab data Martin et al. (2003) CRH(x) DRHLET (NH4)3H(SO4)2 SO42- NH4+ DRHAHS (NH4) HSO4 Forcing calculations DRHAS (NH4)2SO4 aqueous solids Sulfate-water system Deposition (dry and wet) Emission (SO2 and NH3)

  6. Model results % solids 23% 30% 45% 38% Global annual (natural + anthropogenic) burden: 1.938 mg SO42- m-2 % of solids: 34%

  7. (natural + anthropogenic) sulfate aerosol optical thickness % solids 13% 17% 29% 24% Annual global: 0.017; solids: 21%.

  8. optical thickness & full-sky forcing of anthropogenic aerosols % solids % solids 26% 31% 47% 38% 16% 22% 36% 27% Global & annual average of % Solids: 26% in , 31% inFclr, 37% in Ffky.

  9. Sensitivity analysis to the hysteresis effect (compared to base case; anthropogenic component only) : -14% F: -7% : +5% F: +5% Lower side Upper side : +10% F: +8% : 19% F: 12% All aqueous “lower side” and “upper side” difference

  10. Regional difference can be ~20%

  11. Summary & Outlook • Phase transition of sulfate aerosols is now developed in GEOS-Chem. • For anthropogenic component only, solids contribute 26% to sulfate burden, 31% of clear-sky sulfate climate forcing, 37% of full-sky sulfate climate forcing, reflecting the correlation between solids and clear-sky conditions • Hystereisis can result in the uncertainty in the forcing calculations by 12%. • Using upper-side hysteresis loop overestimate forcing by +5%. Regional differences can be up to 20%. • Future research is to look at the implication of modeled results for the study of cirrus cloud formation and modeling of O3.

  12. Thank you !

  13. Sensitivity to other compounded factors

  14. Full-sky (anthropogenic) sulfate direct climate forcing Ffky = Fclr × cloud fraction Annual global: 0.17 Wm-2 Solids: 37% Ffky_sd/Fclry_sd = 0.5 Ffky_aq/Fclr_aq = 0.4

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