WMOD00303

• Title: Observational and Numerical Studies of Cloud and Precipitation Development with a View to Rainfall Enhancement
• Date: 4/1/1992
• Weather Modification - Doc Type: Report

C-D) when mi > 10-4 gm (> 800#-,min diameter). Again rollowing K-M (see also Koenig
(1972) equations 5 to 7) let .

, = "y (2 X 103) tan '"

(20)

and

r ..

e = In [P'(qc + qa) x 10' /'J
In [104] .

(21)

Then

6mi = '(mi x 104)t.

(22)

The growth computations are conducted separately lor categories 4 and 5 (type A and

type B ice). The rate or change in terms or the mixing ratio (O';dl). ~ ...' 1 .. is related
" ,-.,,,,'''' 0"..
to the change in mass by the expression

N.
(Oidl) ;-4,5;i-lor5 = 6qi = 16m;

(23)

where the subscript i denotes the-type ol growth (difFusional or accretional) depending on .
the growth regime. These values are then used in the governing equations lor heat and
moisture conservation (Equations 4 to 9).

In calculating the transler ollatent heat during growth or sublimation in the c:lifierent
regimes it is assumed that the latent heat or sublimation Li. adequately approximates
the processes in the iirst and second regimes (vapor deposition) while the latent heat or
i) condensation Lt. is used in regimes three and four. Although di1fusional growth still occurs
{' in regime three it is assumed that the mass added in this way is negligible compared to
}"
,...~ the mass added by riming growth. Therefore in the conservation equatioDl lor heat and
moisture it is assumed that only riming growth occurs in regimes three and lour. In
addition, it is assumed that depletion olliquid water during riming growth only occurs in
the rainwater :field UDtll it is exhausted whereafter water will be removed from the cloud
water field. This assumption may not be realistic and lurther testing is envisaged to test
this assumption and upgrade the param.eterization.

.

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