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The Global Cycling Of Size-distributed Sea-salt Particles And Their Influence On Sulphate Aerosols

WMO. The Global Cycling Of Size-distributed Sea-salt Particles And Their Influence On Sulphate Aerosols.

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The Global Cycling Of Size-distributed Sea-salt Particles And Their Influence On Sulphate Aerosols

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  1. WMO The Global Cycling Of Size-distributed Sea-salt Particles And Their Influence On Sulphate Aerosols Sun Ling Gong1 and Leonard A. Barrie21Air Quality Research Branch, Meteorological Service of Canada, 4905 Dufferin Street, Toronto, Ontario M3H 5T4, CANADA2Environment Division, AREP, World Meteorological Organization, 7 bis, Avenue de la Paix, BP2300, 1211 Geneva 2

  2. CAM: A Size Segregated Simulation of Atmospheric Aerosol Processes for Climate and Air Quality Models 1. Module Development S.L. Gong1, L.A. Barrie2, J.-P. Blanchet3, K. von Salzen5, U. Lohmann4, G. Lesins4, L. Spacek3, L.M. Zhang1, E. Girard3, H. Lin1, R. Leaitch1, H. Leighton5, P. Chylek4and P. Huang1 2. Global sea-salt aerosol and its budgets S.L. Gong1, L.A. Barrie2 and M. Lazare1 J. Geophy. Res. 2002 (in press)

  3. Model Configurations – CAM/GCM

  4. Global Sea-salt Simulations and Budgets

  5. Global Sea-salt Concentrations

  6. Global Sea-salt Compared with Observations Comparison Sites [WCRP/IGAC COSAM]

  7. Sea-salt Size Distributions (a) Model 995 hPa (b) Quinn et al. [1996] Surface Compare (c) Model 698 hPa (d) Model 197 hPa

  8. Global Sea-salt Residence Times - Coarse

  9. Global Sea-salt Residence Times - Fine

  10. Annual Global Sea-salt Budgets ×1012 kg giga-ton

  11. Global Monthly Sea-salt Emissions

  12. Global Sulphate Aerosols Influenced by Sea-salt

  13. Global Sulphate Concentrations

  14. Global Sulphate Compared with Observations Comparison Sites [WCRP/IGAC COSAM]

  15. Volume Size Distributions 140W, 40S Simulations Quinn et al. 1996

  16. Global Sulphate Distributions

  17. Surface Reduction of Sulphate by Sea-salt -20~30% -10~20% -50~70% -20~30% Rosenfeld et al 2002, Science “Sea-salt cleans air pollution”

  18. Mechanisms of the Sea-salt Impact – (1) • Cleaning Agents • Condensation of sulphuric acid vapour onto existing sea-salt particles reduces the atmospheric sulphate cycling time and hence reduces the sulphate concentrations. • Sea-salt aerosols override the precipitation suppression effects of the large number of small pollution nuclei.

  19. Impact of Sea-salt on Sulphate Number Size Distributions Sea-salt reduces the number concentration of sulphate by enhancing condensation and coagulations.

  20. Mass-mean Diameters of Sulphate (MAM) Increases in MMD reduce the residence time and hence concentrations of sulphate.

  21. Mechanisms of the Sea-salt Impact – (2) • Effects on Clouds • Sea-salt provides additional CCN for SO2 in-cloud oxidation and hence increases the sulphate concentrations. • An increase more than 20% in in-cloud sulphate production due to additional sea-salt particles and higher pH associated with newly formed sea-salt-nucleated cloud droplets compared to sulphate. [O’Dowd et al. 1997, Lowe et al. 1995]

  22. Sea-salt on cloud droplet number Sea-salt aerosols override the precipitation suppression effects of the large number of small pollution nuclei. The enhancement in precipitation helps remove pollution. [Pszenny et al 1998] [O’Dowd et al. 1999] [Rosenfeld et al 2002]

  23. Changes of Sulphate MMR by Sea-salt Competitive processes of sea-salt with positive and negative effects on sulphate. Location dependent. 10~20%

  24. Conclusions • The global annual sea-salt emission to the atmosphere is about 1.01×1013 kg with 68% in the southern hemisphere. • Residence times of 7.7 mm and 0.4 mm diameter sea salt particles in the marine boundary layer were in the range 0.3 - 10 hours and 80 – 360 hours, respectively. • By serving as a quenching agent to nucleation and additional surface area for condensation, sea-salt aerosols increase the mass mean diameter of sulphate aerosols by a factor of 2 and reduce the global sulphate aerosol mass in the surface MBL layer from 5 to 75% for most of the open oceans.

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