Organization and Main Results of the Hail Suppression Program in the Northern Area of the Province of Mendoza, Argentina

Abstract

Cloud seeding activities for hail suppression using rockets are being carried out in the northern area of the Province of Mendoza, Argentina, from 1985 to 1998, with some interruptions. In the operational seasons 1993/94 to 1997/98, Antigrad Latinoamericana has conducted the Program. The target area reaches a surface of 200,000 hectacres, of which 91,500 hectacres are cultivated. The technology is based on the seeding of the hail and potential hail clouds using a mixture of AgI as glaciogenic agent. The method is based on the hypothesis of the acceleration of the precipitation process or early rainout, which assumes the seeding of the area of formation of hail embryos in the periphery of the main updraft and in the area of feeder clouds, resulting in the "rainout" of smaller hydrometeors from less mature, less vigorous clouds. The hydrometeors reach precipitation sizes prior to encountering the stronger updraughts capable of producing hail (WMP Report N° 26. WMO/TD-N° 764). The evaluation of the effectiveness of the Program carried out using the comparison of the historic data on damage hail recorded in the target area in the period in which there were no activities of hail suppression. The average of hail damages to the crops during the 11 seasons with activities of hail suppression in the province of Mendoza was 4.22%, while in a period of 13 years without protection against the hail in the same area this same index was 12.45%.