WMOD00541

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

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7

e:orrelation of model computations to the average 6-hourly precipitation
elf a group of stations on the western (upwind) slope of the Sierra
Nevada Mountains was 0.69. Sarker (1967) obtained good agreement
between model and observed rainfall over the western Ghats of India.

Colton (1976) obtained a good depiction of precipitation amounts over a
watershed. Wilson and Atwater (1972) in other empirical studies showed
the importance of wind direction on precipitation patterns in
Connecticut. Rhea obtained similar results for southwestern Colorado.

The Mrain-shadowing"* effects of upstream barriers on downstream

mountains and valleys have been shown by Rhea et al. (1969) to be

severe, under certain 700 mb level wind directions.

It can be concluded from all of the above studies and some other

considerations such as geographic and topographic similarities, that the
adaptation of a two-dimensional, steady-state model to the Moroccan
Atlas Mountains can be useful not only on a day-to-day operational

basis, but also for some evaluation (of seasonal stream flow, etc.).

In this study, the model description will be addressed in
Section 2. The model adaptation itself will be described in Section 3,

where we will focus on input to the model and some parameter calibration
and sensitivity tests. Section 4 will be devoted to the results and

their discussion. Conclusions will be drawn in Section 5.

*Rain-shadowing can be defined as the sharp decrease of precipitation in
the valleys downstream of the barriers.