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The Randomized Convective Cloud Seeding Experiment in Extended Areas (EXPerimento aleatorizado de siembra de nubes en AReas EXtensas, EXPAREX) is being implemented in Camagüey, Cuba and adjacent regions from August 2005 as the continuation of a previous successful experiment (PCMAT), held in the period [1982][1983][1984][1985][1986][1987][1988][1989][1990]. The first season of the experiment was exploratory and was focused on upgrading facilities, equipment and software, including an An-26 instrumented aircraft and the 10-cm MRL-5 weather radar. It was aimed at implementing methodologies and testing the application of the experimental design, excluding the randomization scheme, which was scheduled to be started in the second experimental year, in the rainy season of 2006. The field operations of the confirmatory phase started only in October, 2006, when seven experimental units, treated under a randomized scheme, were qualified. In the 2007 experiment, 13 more experimental units were processed. The general description, experimental design, procedures and characterization of the first two experimental seasons of the confirmatory phase of EXPAREX are presented in this work. Is it shown that the experimental clouds processed in the first two seasons of the experiment have similar characteristics to the PCMAT clouds, so that the conclusions of previous physical research are applicable. Key words: cloud seeding, precipitation enhancement, cloud physics, convective clouds RESUMO: EXPERIMENTO ALEATÓRIO DE SEMEADURA DE NUVENS CONVECTIVAS EM ÁREAS EXTENSAS EM CUBA (EXPAREX). O Experimento Aleatório de Semeadura de Nuvens Convectivas em áreas extensas (EXPAREX) vemsendo realizado em Camagüey, Cuba e em regiões adjacentes, desde agosto de 2005, como continuação de experiência anterior bem sucedida (PCMAT) realizada entre 1982 e 1990. A primeira temporada do experimento foi exploratória e concentrou-se na modernização das instalações, equipamentos e software, incluindo um avião An-26 instrumentado e um radar meteorológico MRL-5, de comprimento de onda de 10 centímetros. Nesta fase destinou-se a aplicar e testar metodologias, além de definir o desenho experimental, com exclusão do regime de aleatoriedade, que estava programado para ser iniciado no segundo ano, na estação chuvosa de 2006. As operações de campo da fase de confirmação apenas se iniciaram em outubro de 2006, quando sete unidades experimentais, tratadas sob um regime aleatório, foram qualificadas. No experimento de 2007, mais 13 unidades experimentais foram processadas. A descrição geral, delineamento experimental, procedimentos e caracterização das duas primeiras estações experimentais da fase de confirmação de EXPAREX são apresentados neste trabalho. É mostrado que as nuvens experimentais tratadas têm características semelhantes às nuvens do PCMAT, indicando que as conclusões da investigação física obtidas anteriormente são aplicáveis. Palavras-chave: semeadura de nuvens, aumento da precipitação, física de nuvens, nuvens convectivas. 516Martinez-Castro ...

Some results of activities on cloud seeding operations to modify the weather conditions over metropolises are given. The main objective of these activities was to dissipate the clouds and to decrease or to stop the precipitation on the territory under protection during the political, cultural, or sporting events. Up to 12 aircraft specially equipped with the measuring equipment needed to carry out the cloud seeding, with the Land-Aircraft-Land radio data transmission system, and with the cloud seeding means were used to fulfill the works on the weather modification. The liquid nitrogen, "dry ice," silver iodide, and coarse-dispersion powder were used as the reagents for the cloud seeding. To control the aviation works and the results of the cloud seeding, the ground-based automated meteorological radar systems were used. The results of more than 40 large-scale operations on the improvement of weather conditions carried out since 1995 in different regions of Russia and near abroad indicate the efficiency of the methods and technical means of cloud seeding developed by the specialists of Roshydromet to modify the atmospheric precipitation.

Review of methods, used for statistical evaluation of results of artificial precipitation enhancement activities, is given. The historical regression method, modified for statistical evaluation of results of operative works on the artificial precipitation enhancement over large areas, is described. To control the efficiency of operative works, the "floating control method," which uses a variable, or "floating," set of meteorological stations as control stations instead of the fixed one, is proposed to be used. Problems of the criterion choice and the best regression equation search procedure are considered. EVALUATION METHODS OF RESULTS OF ARTIFICIAL PRECIPITATIONENHANCEMENT ACTIVITIES The problem of evaluation of results of active influence on clouds has appeared since the first attempts of such influence. In so doing, the results of the stratus clouds' seeding, which do not produce the precipitation, could often be controlled visually or detected with the help of radar observations [2], but the effects of influence on convective clouds, especially under conditions of natural precipitation falling, are often veiled by processes of their natural evolution. Meanwhile, it is the influence, aimed at the intensification of processes of natural precipitation formation, that provides the obtaining of maximal absolute precipitation increment [1].The complication of the evaluation of active influence results is caused by large spatiotemporal variability of the majority of types of natural processes of precipitation formation, difficulty in the obtaining of their characteristics with accuracy and spatial and temporal resolution, which are necessary for the evaluation of influence results, as well as by the fact that influence effect does not usually exceed the amplitude of natural precipitation variations. On the other hand, in spite of this, in most cases the precipitation increments, induced by the influence, are of great economical importance, that increases still more the significance of the evaluation of efficiency of artificial influence on precipitation formation processes in cloud systems of various types.At the initial stage of works on the artificial precipitation enhancement one tried to obtain the influence efficiency evaluation by means of the comparison of precipitation, falling out during the influence period, with their climatic norm for this period [16]. Subsequently, such attempts have not become widespread, because it became clear that, due to the large natural precipitation variability, exceeding the influence effect by value, one should apply more sensitive methods to evaluate the efficiency. However, since the first works, the researchers paid attention to the close link of two problems, the evaluation of influence efficiency and the evaluation of natural precipitation amount, which could fall out in the case of the influence absence. It is obvious that the exact information on the amount of natural precipitation, which might fall out over the area under influence (target), could enable to determine ...

The description is given of the modern conception and of technical means to carry out the weather modification activities in megalopolises using the active influencing methods. The main objective of these activities is the cloud dissipation and the decrease or cessation of precipitation on the territory under protection. Four influencing methods are commonly used depending on the synoptic situation. To carry out the meteorological protection activities, the airplanes are used equipped with the measuring equipment necessary to execute the influencing, the "land-aircraft-land" system of the radio data traffic and the cloud seeding means. The liquid nitrogen, solid carbonic acid, silver iodide, and coarse-dispersion powder are used as the cloud seeding reagents. To control the aviation activities and the results of cloud seeding, the ground automated radar meteorological complexes are used.