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Parameterization of Ice Growth for Numerical Calculations of Cloud Dynamics

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  • 1 The Rand Corporation, Santa Monica, Calif.
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Abstract

Parametric equations describing the growth of ice particles in the range 10−11–1 g are presented. Three subranges (10−11–5 × 10−8, 5 × 10−8–10−4, and 10−4–1 g) are used. The parametric equations were developed with the aid of a complex method of calculating ice-particle growth. Two approaches to using the parametric equations in a simulation resembling a natural cloud situation are described. One method breaks the ice-particle spectrum into three components, the sizes of each being monitored. The other assumes a size distribution that can be characterized by a “growth-median” size, so that only one size need be monitored to describe the rate of growth. The parametric method is compared with more complicated methods in a simulated cloud environment, and the results are regarded as satisfactory.

Abstract

Parametric equations describing the growth of ice particles in the range 10−11–1 g are presented. Three subranges (10−11–5 × 10−8, 5 × 10−8–10−4, and 10−4–1 g) are used. The parametric equations were developed with the aid of a complex method of calculating ice-particle growth. Two approaches to using the parametric equations in a simulation resembling a natural cloud situation are described. One method breaks the ice-particle spectrum into three components, the sizes of each being monitored. The other assumes a size distribution that can be characterized by a “growth-median” size, so that only one size need be monitored to describe the rate of growth. The parametric method is compared with more complicated methods in a simulated cloud environment, and the results are regarded as satisfactory.

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