WMOD00291

• Title: Bulk Parameterization of the Snow Field in a Cloud Model
• Date: 6/6/1983
• Weather Modification - Doc Type: Report

1080

JOURNAL OF CLIMATE AND APPLIED METEOROLOGY

VOLUME 22

CASE 1

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to

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CASE 2

CASE 3

21

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a

FIG. 6. Numerical simulation of cloud and precipitation for the three cases. The time evolution of Cases I, 2 and 3 are given by the
first, second and third columns, respectively. Fig. 6a shows the evolution of the three cases for the times 21, 24 an4 30 min, while Fig.
6b illustrates the three cases at 36, 42 and 48 min. Cloudy areas are outlined by a solid line. The streamlines are given by dashed lines.
Small solid circles and asterisks indicate rain and hail mixing ratios greater than I g kg-I, respectively. The symbol S and the heavy
{lashes denote snow and cloud ice mixing ratios greater than 0.5 g kg-I, respectively. The normal contour interval (104 kg m-I S-I) for
the streamlines is a factor of 2 lower for times 36 and 42 min for Case I and 24, 36, 42 and 48 min for Case 2.

than 10-3 g g-I because of interactions with the snow
field. There is no rain yet in Case 3 (no autoconver-
sion), and the snow field has just recently been ini-
tiated.
The freezing level is at -3.5 km [all heights above
ground level (AGL)]. Ice crystals (plotted where leI
> 5 X 10-4 g g-l) are depicted in the upper levels of

the cloud in all three cases at 24 min (Fig. 6a). Snow
(>5 X 10-4 g g-I) shows up only in Case 1. At the
same time, considerable amounts of hail (plotted if
values> 10-3 g g-l) are indicated in Cases I and 2,
mainly between 4 and 8 km, while rain is shown in
Case 2 on both sides of the cloud between 3.5 and
5.5 km elevation. Hail has fallen to lower levels in