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Dispersion Aerosol Indirect Effect in Turbulent Clouds: Laboratory Measurements of Effective Radius
Author(s) -
Chandrakar K. K.,
Cantrell W.,
Kostinski A. B.,
Shaw R. A.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl079194
Subject(s) - radius , effective radius , dispersion (optics) , cloud condensation nuclei , aerosol , turbulence , condensation , liquid water content , cloud albedo , albedo (alchemy) , physics , cloud physics , atmospheric sciences , computational physics , cloud computing , environmental science , meteorology , mechanics , optics , astrophysics , cloud cover , operating system , art , computer security , galaxy , performance art , computer science , art history
Cloud optical properties are determined not only by the number density n d and mean radius r ̄ of cloud droplets but also by the shape of the droplet size distribution. The change in cloud optical depth with changing n d , due to the change in distribution shape, is known as the dispersion effect. Droplet relative dispersion is defined as d = σ r / r ̄ . For the first time, a commonly used effective radius parameterization is tested in a controlled laboratory environment by creating a turbulent cloud. Stochastic condensation growth suggests d independent of n d for a nonprecipitating cloud, hence nearly zero albedo susceptibility due to the dispersion effect. However, for size‐dependent removal, such as in a laboratory cloud or highly clean atmospheric conditions, stochastic condensation produces a weak dispersion effect. The albedo susceptibility due to turbulence broadening has the same sign as the Twomey effect and augments it by order 10%.