Small-scale drop-size variability: Empirical models for drop-size-dependent clustering in clouds

By analyzing aircraft measurements of individual drop sizes in clouds, it has been shown in a companion paper that the probability of finding a drop of radius r at a linear scale l decreases as lD(r), where 0, D (r ), 1. This paper shows striking examples of the spatial distribution of large cloud d...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 2005-02, Vol.62 (2), p.551-558
Main Authors: MARSHAK, Alexander, KNYAZIKHIN, Yuri, LARSEN, Michael L, WISCOMBE, Warren J
Format: Article
Language:English
Subjects:
Atmospheric models
Clouds
Cluster analysis
Earth, ocean, space
Exact sciences and technology
External geophysics
Meteorology
Radiative transfer
Rain
Spatial distribution
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Summary:By analyzing aircraft measurements of individual drop sizes in clouds, it has been shown in a companion paper that the probability of finding a drop of radius r at a linear scale l decreases as lD(r), where 0, D (r ), 1. This paper shows striking examples of the spatial distribution of large cloud drops using models that simulate the observed power laws. In contrast to currently used models that assume homogeneity and a Poisson distribution of cloud drops, these models illustrate strong drop clustering, especially with larger drops. The degree of clustering is determined by the observed exponents D (r ). The strong clustering of large drops arises naturally from the observed power-law statistics. This clustering has vital consequences for rain physics, including how fast rain can form. For radiative transfer theory, clustering of large drops enhances their impact on the cloud optical path. The clustering phenomenon also helps explain why remotely sensed cloud drop size is generally larger than that measured in situ.
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-3371.1