WMOD00317

• Contract/Permit #: 14-06-D-6999
• Project Name: CAWRP
• Title: Cascades Atmosphere Water Resources Program - Volume I
• Prepared For: US Department of the Interior Bureau of Reclaimation
• Date: 7/1/1970
• Weather Modification - Doc Type: Report

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mountain are calculated from the continuity equation (see ~3.4.2). It can be

seen from the separations of the streamlines, that the maximum downstream winds

occur just east of the crest and they are about 50% greater than the upstream

velocities. The maximum updrafts and downdrafts are 0.5 and 1.2 m sec-l

respectively.
When blocking is simulated for a westerly airflow the results shown
in Fig. 3.2 are obtained. The method used for simulating blocking is to
modify the ground profile, keeping the height of the mountain peak and its
half-width constant, but changing the ground level at x = - 00 so that the
modified profile of the mountains corresponds to the top of the blocked layer.
The true mountain profile and the simulated profile are both shown in Fig. 3.3.
The effect of simulating blocking is, of course, to reduce the influence of
the mountain on the upstream flow. Thus the maximum winds are now only 20%
greater than the upstream winds. The maximum updrafts and downdrafts are now
-l
0.2 and 0.4 m sec
In the third case (Fig. 3.4), blocking has been simulated in the same
manner as in Fig. 3.3, but the ground profile has been changed to correspond
to southwesterly flow. In this case the Cascade Mountains present several
high peaks at x > O. (The main west-east watershed divide is located at
about x ~ -20 km.) In the region x < 0 the magnitude of the updraft and
downdrafts are of the same magnitude as those shown in Fig. 3.3, and are
significantly less than those shown in Fig. 3.2.
3.3 Cloud Microphysics
Our main interest in this section is to determine the origin of the
precipitation particles which reach the ground as snow in the Cascade