ABSTRACT Convective precipitations associated with storms frequently occur in the Central Andes of Peru. To study these events, statistical estimators of three-dimensional reflectivity, rainfall intensity and microphysical parameters were determined using radar information onboard in the TRMM satellites and the GPM core. As a result, it was found that deeper cloud systems occur in the Andes regions than in the Amazon-Andes transition region. Thus, the difference of the vertical average of reflectivity is around 5 dBZ between both regions. The diurnal rainfall cycle is also different, since it rains preferably at the intervals of 13-23 LST and 18-06 LST respectively. The percentages of occurrence of convective and stratiform precipitation in the areas of the Andes are 30% and 70% respectively and their cumulative contributions to rainfall are 63.3% and 36.7% respectively; however, in the Amazon-Andes transition region, the percentages of occurrence are 31% and 69% and their cumulative contributions to rain are equivalent. It is concluded that convective precipitation in the Andes areas is intensified by the orographic forcing mechanism, which strengthens the growth of hydrometeors above the height of the freezing level between 6 and 12 km of height and leads to greater cumulative rainfall.

RESUMEN Las precipitaciones convectivas asociadas a tormentas ocurren frecuentemente en los Andes Centrales del Perú. Para estudiar estos eventos se determinaron estimadores estadísticos de la reflectividad tri-dimensional, la intensidad de lluvia y parámetros microfísicos usando la información de radares abordo en los satélites del TRMM y el núcleo GPM. Como resultado se encontró que en las regiones de los Andes ocurren sistemas de nubes más profundas que en la región de transición Amazonia-Andes. De tal manera la diferencia del promedio vertical de la reflectividad presenta valores de alrededor de 5 dBZ entre ambas regiones. El ciclo diurno de la lluvia también es diferente, ya que llueve preferentemente en los intervalos 13-23 horas local y 18-06 hora local respectivamente. Los porcentajes de ocurrencia de precipitación convectiva y estratiforme en las áreas de los Andes son 30% y 70% respectivamente y sus contribuciones acumulativas a la lluvia son 63.3% y 36.7% respectivamente; en cambio en la región de transición Amazonia-Andes, los porcentajes de ocurrencia son 31% y 69% y sus contribuciones acumulativas a la lluvia son equivalentes. Se concluye que la precipitación convectiva en las áreas de Andes se intensifica con el mecanismo de forzamiento orográfico, lo que fortalece el crecimiento de los hidrometeoros por encima de la altura del nivel de congelación entre 6 y 12 km de altura y propicia mayores acumulados de lluvia.

O Experimento Aleatório de Semeadura de Nuvens Convectivas em áreas extensas (EXPAREX) vem sendo 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.

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 1982-1990. 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.