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

- 62 -

Eqn. (3.62) is the appropriate equation for the flow of cloudy air over

a mountain and it can be seen that it is of the same form as eqn, (~.l5) for

dry air. Therefore, within the limits of the assumptions, each solution of

eqn. (3.l5) also represents a solution for a variety of completely cloudy

atmospheres.

3.2.3 Boundary Conditions and Assumptions

Since the equatlon for the flow of cloudy air over a mountain is of the

same form as that for dry air, there should be no inherent difficulty in

constructing a multi-layer model which contains both dry and cloudy air, This

i~, in fact, the case provided the layers are continuous in the x-direction.

However, if the cloud layer is discontinuous (e.g. if it evaporates downwind)

the superimposition technique fails. Since our main interest is in the details

of the airflow upwind of the mountain (where in the case of the Cascade

Mountains the cloudy ail' is extensive) rather than in lee waves (which are

excluded anyway by the broad mountaitt assumption), this restriction is not

serious.

In the present version of the model, the atmosphere is divided into

three layers the middle layer of which is cloudy.. The boundaries between

these layers are determined from the upwind sounding of re~ative humidity.

The boundary conditions, which are non-linear~ are that ~ and ;)r,;/dz are

continuous across the boundaries between the three layers. The positions of

the bounding streamlines are determined by an iterative scheme.

In order to include some of the three dimensional features of the

terrain into the two dimensional model, the. profile of the Cascade Mountains

is varied depending on the direction of the wind.

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