Distribuição das chuvas no município de Tangará da Serra, médio norte do Estado de Mato Grosso, Brasil.

It is of great importance to know the rain distribution in the region of Tangará da Serra (latitude 14°37′55″S, longitude 57°28′05″W and altitude 488 m), as it is an agricultural region, which makes such information essential for an adequate planning, maximization of agricultural potential and optimization of hydric resources. Thus, this work was aimed at evaluating the annual, monthly and ten-day pluviometric variability, and also quantifying the number of dry and rainy days and different levels of rain probability for the region. Pluviometric data provided by ′Agência Nacional de Águas′ (ANA) were used to analyze a period of 38 years (from January 1970 to December 2007). Precipitation behavior in Tangará da Serra has annual and monthly variations, constituting two well defined seasons - a dry one from May to September, and a rainy one from October to April. Annual variability during the analyzed period corresponds to the maximum value of 2,861, minimum of 1,404 and average of 1,830 mm, respectively. The incomplete gamma function adequately expresses precipitation probability in Tangará da Serra. Precipitation averages range from 40 to 50% probability for rainy months and from 30 to 40% for dry ones. According to the results, this type of research might help the elaboration and development of irrigation projects in this region. [ABSTRACT FROM AUTHOR]