Analysis of space and seasonal variation and trends in the precipitation of the southern region of Brazil

Abstract

The precipitation distribution has a great influence on the agricultural production and economy of the southern region of Brazil. This study aimed to evaluate the spatial and seasonal distribution and trends in the precipitation series of the southern region of Brazil. For this purpose, we used data from 197 rain gauges located in the Southern Region of Brazil, which presented more than 32 years of data in the annual series from 1976 to 2015. The annual and seasonal precipitation series and the Precipitation Concentration Index (PCI) were obtained. The trend in the series was evaluated by the Mann-Kendall test at a significance level of 5%. The maps showing the spatial and seasonal variation of both precipitation and PCI were presented. The results show that the series can be considered stationary, since more than 83% of the rainfall stations did not present significant trends of increase or reduction in the volume of precipitation nor in the concentration of rain on the region under study. In terms of seasonality of precipitation, there were also no significant trends there, although some seasonal and spatial variations were detected, so that in summer there is a greater number of seasons that show increasing precipitation trends, and in autumn the tendency is for reduction.