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The effect of physical and chemical aerosol properties on warm cloud droplet activation

July 2006
Atmospheric Chemistry and Physics 6(9)

July 2006
6(9)

DOI:10.5194/acpd-5-8507-2005

License
CC BY 4.0

Authors:

Paulo Artaxo

University of São Paulo

Urs Baltensperger

Paul Scherrer Institut

Show all 15 authorsHide

The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the 'indirect effects' are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.

The Köhler equation can be envisaged as the competition between the curvature (Kelvin) and solute (Raoult) terms.

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. Hygroscopic growth factors of various "pure" substances. GF at 90% RH

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. Hygroscopic behaviour of Aitken mode particles in various environments. upper Aitken mode size range (∼50-80 nm)

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Simulation showing the change in droplet radius with height in a simulation initialised with an ammonium sulphate aerosol with a geometric mean diameter of 140 nm, a geometric standard deviation, σ g of 1.7 and aerosol number concentration of 300 cm −3 (corresponding to a total mass loading of 0.76 µgm −3 ). The simulation was started at an RH of 95% at 1000 m. Solid lines represent selected aerosol size classes. The dashed line is the saturation ratio.

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. Hygroscopic behaviour of accumulation mode particles in various environments. lower accumulation mode size range (∼100-150 nm)

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Comments on "Influence of soluble surfactant properties on the activation of aerosol particles containing inorganic solute'' - Reply

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