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The recorded historical series of precipitation are usually available for short periods of time and with many failures. The use of mathematical modeling to simulate rainfall is a tool used to circumvent this problem and to simulate the operation of water systems in different scenarios. The present study applies mathematical modeling to the hourly pluviometric precipitation data simulation. A pluviographical data set from October 1980 to December 2007 was used in the study. Precipitation data sets were obtained through daily pluviometric digitalization from the Meteorologic Station of Epagri at Urussanga, in southern Santa Catarina, Brazil (latitude 28° 31' S and longitude 48° 19' W). To simulate the hourly rain series, the stochastic model was modified based on the Bartlett-Lewis rectangular pulses model with six parameters. Those parameters were fitted by minimizing a function related to the analytical expressions that define the average, variance, and autocorrelation coefficient at lag 1 and the probability of a dry period related to the estimated values from the observed data. Ten series were simulated for 100 years of data. Data analyses and results showed that fitting Bartlett-Lewis model parameters makes it possible to simulate hourly rainfall while preserving precipitation statistical properties at several temporal aggregation levels. In general, the probability of dry periods tended to be overestimated. [ABSTRACT FROM AUTHOR]

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]