1. An annual cycle of size-resolved aerosol hygroscopicity at a forested site in Colorado Ezra Levin A.J. Prenni, S.M. Kreidenweis, M.D. Petters, R.C. Sullivan, S.A. Atwood, J. Ortega, P.J. DeMott and J.N. Smith Funded by: NSF (ATM-0919042) AMS Annual Meeting 1/24/12

2. (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H 2 O, Organics & Nitrogen) BEACHON What are the impacts of biogenic emissions on aerosol hygroscopicity and CCN concentrations?

3. [Levin et al, 2009; Schichtel et al, 2008] Regional aerosol 21% 45% Modern C Fossil C We expect biogenic organics to be important, especially in the summer

4. Size resolved cloud condensation nuclei Total N CCN DcDc

5. Hygroscopicity parameter: kappa κ = 0.1 κ = 0.6 [Petters and Kreidenweis, 2007] SOA Ammonium Sulfate

6. 0.13 ± 0.04 0.14 ± 0.05 0.15 ± 0.05 0.17 ± 0.06 0.22 ± 0.12 48 ± 3 54 ± 5 66 ± 2 85 ± 3 147 ± 14 Kappa Activation Diameter Kappa timeline Low kappa indicates large organic component

7. Kappa and CCN have a seasonal cycle Why do kappa and CCN change with season and size? Largest particles are more variable. Smallest particles consistently low.

8. New particle formation

9. At larger diameters, New particles have lower hygroscopicity.

10. New particle formation NPF affects aerosol hygroscopicity and CCN concentration. SOA

11. Conclusions The aerosol in Manitou Forest is highly organic dominated. New particle formation appears to depress kappa but increase CCN. It is likely that the new CCN have a large biogenic organic component, thus linking the biosphere, hydrosphere and atmosphere.