WMOD00541

• Title: Adaptation of the Rhea Winter Orographic Precipitation Model to Morocco
• Date: 4/1/1989
• Weather Modification - Doc Type: Report

but most are two-dimensional (2-D) (in the x-z plane) [e.g., Myers,
1962; Sarker, 1967; Willis, 1970; Fraser et a1., 1973; P100ster and
Fukuta, 1974; and Young, 1974]. The majority of the above mentioned 2-D
models are steady-state and are based on simple assumptions (adiabatic
flow, no friction, idealized sinusoidal mountains). Some exceptions to
the above simplified 2-D models (designed for a flow solution) are found
in Myers (1962) and Elliott (1969) who use a more realistic approach,
such as simulating a more realistic topography and using the mass
continuity, hydrostatic, and thermodynamic energy equations.
We mentioned that a few 3-D models have been developed. These
models certainly have the advantage of more realistic simulation of the
overall topographic effects on the flow, which the 2-D models do not
have. On the other hand, more computational time is required (10 to 100
times more than that required by the 2-D models), which can constitute a
serious disadvantage. For example, the present version of the 2-D model
being used for this study requires only 30 seconds for one "wetn sound-
ing to be processed on an IBM-PC.
In these 2-D and 3-D models, treatment of atmospheric water
substances varies from the assumption that all water which condenses
precipitates (Myers, 1962; Sarker, 1967; Colton, 1975) to rather complex
cloud physics considerations for the amount of precipitation (Young,
1974; Nickerson et a1., 1976). With some exceptions, these models were
essentially developed to be used as aids to cloud physics or weather
modification research.
The model results have had limited comparisons with observations.
In a test over a winter season of the model by Myers (1962), the linear

6

I
t
I
I
I
I
I
I
I
I
I
,
I
I
I
I
I
I
I