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An annual cycle of size-resolved aerosol
hygroscopicity at a forested site in Colorado
Ezra LevinA.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
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(Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen)
BEACHON
What are the impacts of biogenic emissions on aerosol hygroscopicity and CCN concentrations?
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[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
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Size resolved cloud condensation nuclei
Total NCCN
Dc
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Hygroscopicity parameter: kappa
DRT
M
DD
DDDS
w
Was
d
d
/
33
33 4exp
1)(
κ = 0.1
κ = 0.6
[Petters and Kreidenweis, 2007]
SOA
Ammonium Sulfate
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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
KappaActivation Diameter
Kappa timeline
Low kappa indicates large organic component
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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.
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New particle formation
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New particle formation
At larger diameters, New particles have lower hygroscopicity.
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New particle formation
NPF affects aerosol hygroscopicity and CCN concentration.
SOA
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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.