WMOD00401

• Contract/Permit #: 2-07-81-V0256
• Title: Precipitation Development in Seeded Clouds Over the Sierra Nevada
• Date: 8/1/1986
• Weather Modification - Doc Type: Report

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Beheng (1978) performed calculations of graupel developnent.

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His calculations included:

i) simul taneous treatment of

coalescence and graupel growth; ii) interaction between the

graupel growth and the droplet spectrum, so that the growing

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graupel depleted the cloud water; i i i) stochastic collisions.

When coalescence occurred simultaneously with the riming process

the two interacted strongly.

The depletion of the water by the

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growing graupel led to tile inhibition of the coalescence process.

Heymsfield (1982) calculated the growth rates of a variety of

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particle types by diffusion, accretion, "dry" or "wet" growth and

melting.

The particlE!s were grown in a region of updraft.

At

LWC=l g m-3, frozen drops grew most rapidly, followed in order by

graupel, aggregates and planar crystals.

This model is described

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in section 4.1 and is the basis for many of the calculations in

this thesis.

Heymsfield and Pflaum (1985) calculated the growth of graupel

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and compared wi th experimental graupel growth of pflaum and

Pruppacher (1979).

~~he calculations were performed using the

basic growth equations of diffusion and accretion. The

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accretional growth was calculated using four methods of collection

efficiency:

First, the momentum approach, where the results of

Pflaum and Pruppacher (1979) were used which showed the graupel

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collection kernal to be equal to that of a water drop with the

same momentum.

Second, a theoretical approach developed by Hall

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(1980) and Rasmussen and Heymsfield (1985) which uses Pflaum and

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Pruppacher I s finding that the parameter controlling the trajectOl::Y

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