Monoterpene New Particle Formation Events’

Contribution to CCN in the Boreal Forrest and Globally

Lexie Goldberger ATMS 591

Stations Measuring Atmosphere Ecosystem Relationships II (SMEAR

II), Hyytiälä Finland

• SMEAR field station of the Atmospheric Research Center and the Department of Physics of the University of Helsinki

• DMPS (Differential Mobility Particle Sizer)

SMEAR

SMEAR

Boreal Forrest

Monoterpenes, C10H16

Station Conditions

Wikipedia

SMEAR data

Köhler curve dependence on composition versus size

Köhler curve for ammonium sulfate particles and various hygroscopicity (Farmer et al. 2014) (Dusek et al. 2006)

Köhler curves for ammonium sulfate particles (similar molar mass to monoterpenes) with dry particle diameters ranging from 10 to 490 nm, in 20 nm steps. Critical supersaturation is the percent supersaturation at the maximum of each curve. The line color indicates the particle dry diameter. The gray-filled region indicates where s < 1.0% and the yellow-filled region where s < 0.3%. Note the decrease in the critical supersaturation with increasing particle size. (B) Köhler curves for particles with 80 nm dry diameters but differing composition. Particles have been chosen to represent highly hygroscopic (NaCl), very hygroscopic (ammonium sulfate), moderately hygroscopic (oxidized organic aerosol), weakly hygroscopic (primary organic aerosol), and non-hygroscopic (black carbon) materials.

What are CCN

CCN = particles that can activate at a given supersaturation

CCN dependent on both size and composition

For this project I use Dp=48nm as the cut off size for CCN based off literature values (Varutbangkul et al. 2006 for S=1%, monoterpene can be treated as a highly water-soluble organic) This can be justified using the Köhler curve on the previous page.

for a given aerosol population with a uniform, size-independent composition, number density of CCN activated:

CCN(s)=∫[Ds:∞] n(Dp)dDp, where n(Dp) is number distribution and Ds is the activation diameter for s% supersaturation for these particles

simplified: CCN(s)=cs^k, for continental aerosols assuming a supersaturation of .4% for low clouds, CCN(.4%) = 600*0.4^.5 = 379.5 cm^-3, (values from Hegg and Hobbs 1992)

Banana Plots

Banana Plot Zoom

Change in CCNCCN(1.0%)

Particle Size Distribution

Growth of Particles

Linear Growth Rate, (*accumulation of mass is exponential)

Effect of SOA, ELVOC, and isoprene on annual average CN, CCN(1.0%), and

CCN(0.2%)

Jokinen et al. 2015

ELVOC promote aerosol particle

formation and CCN production in the

atmosphere. Monoterpenes with

their endocyclic double bound readily produce ELVOC from

ozonolysis.

Monoterpene oxidation products

enhance atmospheric new particle

formation and growth in continental regions,

increasing CCN concentrations.

Isoprene derived SOA suppresses

atmospheric new particle formation but assists in the growth

of sub-CCN-size primary particles to

CCN