Scientific Theme: Advanced Modeling and Observing Systems

Scientific Theme: Regional Processes
sugars, dicarboxylic acids and complex mixtures of water-soluble organic compounds. Finally, fRHext(80% RH,
dry) was found to vary linearly with the organic/inorganic content, allowing for simple incorporation of organic
properties into atmospheric models. Investigators derived a generalization of fRHext(80% RH, dry) = 2.90 –
0.015(wt% organic species) for a particle size distribution with a dry mean optical diameter of 0.35 μm. This
parameterization for ammonium sulfate/water-soluble organic aerosol is applicable to the fine particle mode fraction
of atmospheric aerosol. Information necessary to incorporate the variation in the size distribution is also included.
This suggests that neglecting the water uptake by the organic fraction of atmospheric particles could lead to
significant underestimation of the cooling at the Earth‘s surface due to light scattering by aerosol.
Right. Measured fRHext(80% RH, dry) for
ammonium sulfate mixed with adipic acid
(solid squares), DL-malic acid (crosses),
glucose (open triangles), levoglucosan (open
circles) and mannitol (open square). The top
dashed line is the best fit to the sugar data (all
open symbols) and the middle dashed line is
the best fit to the dicarboxylic acid data. The
solid black line models the case where water
uptake is dictated only by ammonium sulfate
(labeled ―Linear Fit w/ fRH(org) = 1‖).
100
Left. Variation of fσ(ep)(80% RH, Dry) with dry
effective optical diameter for λ = 532 nm.
Shown are 100% NaCl (solid circle), 50 wt%
NaCl and 50 wt% organic mixture A (open
circle), 100% (NH4)2SO4 (solid square), 50
wt% (NH4)2SO4 and 50 wt% organic mixture B
(open square), 100% organic mixture A (+),
and 100% organic mixture B (×).
MILESTONE CSD09.4:
Measure particle nucleation and particle growth rates in laboratory experiments following the gasphase
oxidation of biogenic monoterpene compounds by O3 and the OH radical.
ACCOMPLISHMENTS FOR CSD09.4:
Measurements of particle nucleation following the gas-phase oxidation of α pinene and β pinene were measured.
Particle nucleation following the ozonolysis and O3 plus OH initiated monoterpene oxidation was measured in a 70
L Teflon bag reactor over the temperature range 278 K to 320 K. Particle concentration temporal profiles were
measured for a range of initial monoterpene and ozone concentrations using ultra-fine condensation particle