Rainfall in Maringá-PR: descriptive statistics, long-term trend and probability of daily extreme events

Abstract

The aim of this paper was to expose an overview of the rainfall measured at the Principal climatological station of Maringá, encompassing the period from 1980 to 2018. Four objectives outlined the research: i) obtaining descriptive statistics; ii) long-term trend evaluation; iii) probability distribution assessment of the daily rainfall, and iv) analysis of the consecutive wet days. Besides the general pattern of wet and dry periods, it was observed local maxima of rainfall in May and October. The long-term trends were evaluated by means of the linear regression, whereupon no significant trends were found. Nevertheless, by means of the mean test, it was verified that the recent years (2013 to 2018) were wetter than the remaining series (1980 to 2012). The Gamma distribution showed the best fit between the database and the theoretical distribution. In May, September and October the estimated daily volumes are higher than those estimated for other months. The period of highest number of consecutive wet days is between October and March. By the other side, the largest volumes per event happen in this period and in the following months: May and September. Although in the seasons of autumn and spring the monthly accumulated rainfall is lower than rainfall in the months of summer, in those seasons happen expressive daily rainfall, which extremes are larger than in the summer. This characteristic is related to the intensified action of low-pressure atmospheric systems, mainly troughs and early or late frontal systems.