WMOD00482

• Title: Microphysical Observations Over the Atlas Mountains in Morocco
• Date: 12/23/1988
• Weather Modification - Doc Type: Report

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1. INTRODUCTION

During the past decade, Morocco has experienced an extended period of drought.

Normally, Morocco's climate is Mediterranean, with most of its precipitation occurring

during the winter months as a result of frontal passages. The High Atlas Mountains,
which extend from the southwest to the northeast end of the country, are a formidable
barrier to the oncoming fronts, with peaks over 4 km elevation at some locations (Fig. 1).
Most of the moisture falls out as snow on the western side of the barrier, with very little

precipitation falling on the lee side. In an attempt to improve the precipitation efficiency

during the passage of these fronts, the government of Morocco with U.S. AID support
initiated a program (The Al Ghait Snowpack Enhancement Programme) to enhance the
snow fall over the Atlas mountains by cloud seeding.
As part of the background work for this program, cloud physics data was
collected over the Atlas mountains by the University of North Dakota Citation n aircraft.
Data were collected between January 1985 through December 1985. We present herein a
case study from December 8 and 9,1985. The data were collected over the ponion of the

Atlas mountains located 200 km southeast of Casablanca (Fig. 1). The goal of the current

study is to determine some of the natural precipitation processes active over the Atlas
mountains during winter frontal passages.

2. SYNOPTIC WEATHER DESCRIPTION

On December 8, 1985, a cold front passed over Morocco. The surface analysis
(Fig. 2) shows the 12Z position of the front on Dec.?, 8, and 9. Associated with this front
was an extensive cloud shield, shown in the visible satellite photograph at 1230Z on Dec.
8 (Fig. 3a). Between Dec. 8 and Dec. 9, the front passed over the Atlas mountains, and
by Dec. 9, 12Z the organized cloud shield associated with the front has dissi.pated over