WMOD00289 ‎(2)‎

• Title: Observations and Numerical Simulations of Precipitation Mechanisms in Natural and Seeded Convective Clouds
• Prepared By: Lroen D. Nelson
• Date: 3/1/1979
• State: IL
• Weather Modification - Doc Type: Report

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number density set by the melting rate of that hailstone. Thus, total mass continuity

is maintained while hailstones melt away in mass at constant number density to re-

appear as variable number densities of conserved mass raindrops. Any particles

formed too large for physically realistic raindrops are assumed to immediately break

up via the breakup term of Srivastava (1971). This process thus maximizes the

rate of transfer of hail mess to large raindrops and may tend to underestimate the

hail amounts reaching the ground in relation in total rainfall.

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Dynamics

General Framework

The cloud in this work is modeled as a radially symmetric cylindrical air

column with a time independent radius in an environment at rest. The pressure in

the column is assumed to adjust instantaneously at each level to that of the environment

which is assumed to be in a state of hydrostatic equilibrium. All equations are formu-

lated in one-climensional space in a manner similar to that of Asai (1962), Asai and

Kasahara (1967) and Ogura and Takahashi (1971) with respect to the dynamic terms.

The system of equations formulated in this work is that used by Nelson (1971) and

greatly expanded by Silverman and Glass (1973) to permit realistic simulation of

time dependent tropical warm cumulus clouds. This study will further expand the

dynamical framework and microphysical-dynamic interaction terms to allow for ice

and ice-processes and to thus permit the simulation of continental clouds in which

the ice phase may playa significant role in precipitation production.