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

2. Meteorological Service of Canada Environment Canada CAM: A Size Segregated Simulation of Atmospheric Aerosol Processes for Climate and Air Quality Models J. Geophy. Res. 2002 (in press) 1.Module Development S.L. Gong 1, L.A. Barrie 2, J.-P. Blanchet 3, K. von Salzen 5, U. Lohmann 4, G. Lesins 4, L. Spacek 3, L.M. Zhang 1, E. Girard 3, H. Lin 1, R. Leaitch 1, H. Leighton 5, P. Chylek 4 and P. Huang 1 2. Global sea-salt aerosol and its budgets S.L. Gong 1, L.A. Barrie 2 and M. Lazare 1

3. Meteorological Service of Canada Environment Canada Model Configurations – CAM/GCM

4. Meteorological Service of Canada Environment Canada Global Sea-salt Simulations and Budgets

5. Meteorological Service of Canada Environment Canada Global Sea-salt Concentrations

6. Meteorological Service of Canada Environment Canada Global Sea-salt Compared with Observations Comparison Sites [WCRP/IGAC COSAM]

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

8. Meteorological Service of Canada Environment Canada Global Sea-salt Residence Times - Coarse

9. Meteorological Service of Canada Environment Canada Global Sea-salt Residence Times - Fine

10. Meteorological Service of Canada Environment Canada Annual Global Sea-salt Budgets ×10 12 kg giga-ton

11. Meteorological Service of Canada Environment Canada Global Monthly Sea-salt Emissions

12. Meteorological Service of Canada Environment Canada Global Sulphate Aerosols Influenced by Sea-salt

13. Meteorological Service of Canada Environment Canada Global Sulphate Concentrations

14. Meteorological Service of Canada Environment Canada Global Sulphate Compared with Observations Comparison Sites [WCRP/IGAC COSAM]

15. Meteorological Service of Canada Environment Canada Volume Size Distributions Quinn et al. 1996 Simulations 140W, 40S

16. Meteorological Service of Canada Environment Canada Global Sulphate Distributions

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

18. Meteorological Service of Canada Environment Canada 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. Meteorological Service of Canada Environment Canada Impact of Sea- salt on Sulphate Number Size Distributions Sea-salt reduces the number concentration of sulphate by enhancing condensation and coagulations.

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

21. Meteorological Service of Canada Environment Canada Mechanisms of the Sea-salt Impact – (2) Effects on Clouds –Sea-salt provides additional CCN for SO 2 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. Meteorological Service of Canada Environment Canada Sea-salt on cloud droplet number [Pszenny et al 1998] [O’Dowd et al. 1999] [Rosenfeld et al 2002] Sea-salt aerosols override the precipitation suppression effects of the large number of small pollution nuclei. The enhancement in precipitation helps remove pollution.

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

24. Meteorological Service of Canada Environment CanadaConclusions The global annual sea-salt emission to the atmosphere is about 1.01×10 13 kg with 68% in the southern hemisphere. Residence times of 7.7  m and 0.4  m 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.