1. Biogenic Secondary Organic Aerosol Formation Michael Boy ASP / ACD / NCAR

3. What is the main process concerning SOA formation ? Nucleation ! Condensational growth ! We suggest that the growth of clusters to a detectable sice is restricted by the availability of condensable vapour. Observations of atmospheric particle formation and growth from a continental and a coastal site support this hypothesis, including that a growth process including ternary nucleation is likely to be responsible for the formation of CCN. Kulmala et al., Nature 2000

4. M. Kulmala et at., Aerosol Science 35 (2004), p. 143-176 Where do we observe SOA formation ?

5. How many SOA formation events per year ?

6. Seasonal trend of SOA formation events ? M. Kulmala et at., Aerosol Science 35 (2004), p. 143-176 Rural area in Finland Rural area in Germany Urban area in USA

7. Is SOA formation a local effect ? (Stratmann et al., ACP 2003, Vol. 3)

8. (Stratmann et al., ACP 2003) Vertical distribution of new formed particles

9. How fast do the new formed particles grow ? Kulmala et at., Aerosol Science 2004, Vol. 35 Polar regions: 0.1 nm h -1 Coastal areas: 200 nm h -1

10. How many particles are produced per time ? Urban areas: up to 100 # cm -3 s -1 Coastal zones: up to 10 4 -10 5 # cm -3 s -1 Industrial plumes: up to 10 4 -10 5 # cm -3 s -1

11. ________________________________________________________________________________________ University of Helsinki 3 nm Free troposphere Mixed layer 1 nm Formation of TSCs Binary nucleation: H2SO4 + H2O Ternary nucleation: H2SO4 + NH3 + H2O Ion induced nucleation Nucleation of organics

12. ________________________________________________________________________________________ University of Helsinki 3 nm Free troposphere Mixed layer Production of condensable vapours Ozone 1 nm Formation of TSCs Production of condensable vapours Sulphuric acid Monotepenes reaction products Sesquiterpenes reaction products ????

13. ________________________________________________________________________________________ University of Helsinki 3 nm Free troposphere Condensation Coagulation Deposition Mixed layer Production of condensable vapours Ozone Condensation & Coagulation 1 nm Formation of TSCs

14. Weber et al., JGR (1997) 102 Fiedler et al., ACPD (2005) Sulfuric acid and nucleation mode particles ?

15. Date Growth rateGR(H 2 SO 4 ) DMPSH 2 SO 4 / GR(DMPS) [nm h -1 ] [%] 19.3.20031,00,066,1 20.3.20031,50,1510,2 21.3.20032,60,249,1 25.3.20032,50,156,1 26.3.20033,60,318,6 29.3.20033,60,174,8 31.3.20033,50,236,7 2.4.20032,40,4016,9 3.4.20033,80,287,3 6.4.20031,80,168,7 7.4.20032,90,3913,5 Average2,70,28,9

17. Intermedia step for global models Influence on CCN UHMA (University of Helsinki Multicomponent Aerosol code) Chemistry subroutine (67 species) BLMARC (1-dimensionsal model) Emission scheme for different biospheres Extended organic chemistry scheme Condensation of organics Information on the secrets of SOA formation Ion induced nucleation

18. 1-D-Model trajectory Thanks !!!