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Article
Influences of Drizzle on Stratocumulus Cloudiness and Organization
Journal of Geophysical Research - Atmospheres
  • Xiaoli Zhou, McGill University
  • Thijs Heus, Cleveland State University
  • Pavlos Kollias, State University of New York at Stony Brook
Document Type
Article
Publication Date
7-17-2017
Disciplines
Abstract

Large-eddy simulations are used to study the influence of drizzle on stratocumulus organization, based on measurements made as part of the Second Dynamics and Chemistry of the Marine Stratocumulus field study-II. Cloud droplet number concentration (Nc) is prescribed and considered as the proxy for different aerosol loadings. Our study shows that the amount of cloudiness does not decrease linearly with precipitation rate. An Nc threshold is observed below which the removal of cloud water via precipitation efficiently reduces cloud depth, allowing evaporation to become efficient and quickly remove the remaining thin clouds, facilitating a fast transition from closed cells to open cells. Using Fourier analysis, stratocumulus length scales are found to increase with drizzle rates. Raindrop evaporation below 300 m lowers the cloud bases and amplifies moisture variances in the subcloud layer, while it does not alter the horizontal scales in the cloud layer, suggesting that moist cold pool dynamic forcings are not essential for mesoscale organization of stratocumulus. The cloud scales are greatly increased when the boundary layer is too deep to maintain well mixed.

DOI
10.1002/2017JD026641
Citation Information
Xiaoli Zhou, Thijs Heus and Pavlos Kollias. "Influences of Drizzle on Stratocumulus Cloudiness and Organization" Journal of Geophysical Research - Atmospheres Vol. 122 Iss. 13 (2017) p. 6989 - 7003
Available at: http://works.bepress.com/thijs-heus/12/