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<br />To be published In the proceedings of the <br />Fifth WMO Conference on Weather Modfflc8llon and Applied Cloud Physics <br />Beijing, China <br /> <br />SEEDABILITY OF MOROCCAN CLOUDS <br /> <br />O. Baddour. M. Nbou, and M. EI Mokhtari <br />Direction de la Meteorologie Nationale <br />Casablanca, Morocco <br /> <br />R. M. Rasmussent, D. B. Johnsont, and D. A. Matthews <br />Bureau of Reclamation <br />Denver, Colorado 80225 <br />USA <br /> <br />1. INTRODUCTION <br /> <br />Since 1984 Morocco has been conducting a <br />snowpack enhancement project called Pro- <br />gramme AI Ghait (see Bensari et al., 1989) <br />over the Atlas mountains. The project uses <br />silver iodide seeding techniques in an attempt <br />to supply the Oued Oum Er Rbia watershed <br />with additional water. An integral part of this <br />project has been the scientific analysis and <br />evaluation of cloud physics data for the de- <br />termination of cloud seedability. Cloud <br />physics data for this purpose were collected by <br />the University of North Dakota (USA) Cita- <br />tion aircraft during the period of January <br />through December t985. Analysis of this data <br /> <br />320. <br /> <br />Rabat <br /> <br />o <br />Meknes <br /> <br />Atlantic <br />Ocean <br /> <br /> <br /> <br /> <br />KhouribgaO. <br /> <br />Marrakech <br />o <br /> <br />';....~:.~~.~. <br /> <br />Figure 1. Map of Central Morocco showing the <br />principal cities and major terrain features. <br />The elevation contours are shaded in 500 m <br />intervals. <br /> <br />set has been presented in Baddour and Ras- <br />mussen (1988). Since 1987, cloud physics data <br />have been collected with an instrumented <br />Moroccan King Air 100 aircraft. <br /> <br />The present study is part of an ongoing ef- <br />fort to estimate the seedability of the clouds <br />forming over the Atlas mountains using the <br />data collected by the Moroccan cloud physics <br />aireraft. In order to do this, we subdivide the <br />clouds into categories based on clouds sampled <br />between November 1987 through April 1988. <br />Twenty one cases were analyzed using liquid <br />water content and ice particle concentration <br />as the primary parameters characterizing the <br />cloud. Cloud categories were based on air- <br />er.aft, rawinsonde, satellite, and radar data. <br /> <br />2.. ANALYSIS APPROACH <br /> <br />152" <br /> <br />The analysis approach used herein was <br />motivated by the regions of potential tech- <br />nique used in the Precipitation Enhancement <br />Program (PEP), (e.g. Vali et al., 1988). We <br />were not able, however, to fully implement <br />this technique due to the lack of appropriate <br />data. In the current study, the clouds were <br />classified into three classes according to their <br />sl:ability an~ airmass characteristics using <br />aJlreraft, rawmsonde, radar, and satellite data. <br />The radar data were obtained from a C-band <br />W cm wavelength) 1.6 degree beamwidth <br />radar located near Khouribga, on a plateau <br />midway between the Atlantic Ocean and the <br />Atlas Mountains (see Figures 1 and 2). Avail- <br />able satellite data include both visible and IR <br />images. Aircraft data for each cloud class <br />were then analyzed according to their <br />microphysical characteristics using the one <br />second values of supercooled liquid water con- <br />tent from the Johnson-Williams probe. and <br />one second value of ice particle concentration <br />from an optical ice particle counter. <br />A frequency plot using these data was con- <br />structed for each cloud category. <br /> <br />t Current affiliation: Applied Research Corporation, <br />3005 Center Green Drive, Suite 225, Boulder, Colorado <br />80301, USA. <br />