Rainfall in the Midwest region and in the State of Tocantins/Brazil: historical analysis and future trend

Abstract

Meteorological phenomena are the result of climatic variations which can be observed during a series in order to detect trends or changes in hydrometeorological time series. Aiming to analyze the rainfall and the future trend of rainfall in the Midwest and the state of Tocantins, a study was carried out with linear regression and measures of central tendency and dispersion of rainfall from rain. We used 261 rainfall stations with 30 years of data. We used the average monthly and annual precipitation series of historical rainfall data obtained by the National Hydrometeorology, submitted to a preliminary analysis. The statistic calculated the mean, median and standard deviation of rainfall time needed to check the parameters, and observed the dispersion of the sample. There is a downward trend in average rainfall between 1977 and 2006 for the Midwest region and the State of Tocantins, in the order of 6.5%. Only the months of March and April showed growth of precipitation. Throughout this paper presents the temporal distribution, linear regression analysis and statistics, future trends, and monthly and annual variation of rainfall from the historical average for the Midwest region and the State of Tocantins.