Variations of Rainfall Rhythm in Alto Pardo Watershed, Brazil: Analysis of Two Specific Years, a Wet and a Dry One, and Their Relation with the River Flow

Abstract

This research aims to understand the variability and rhythm of rainfall for two specific standard-years, and their relation with the river flow of the Alto Pardo watershed, located in southeastern Brazil, and thus identify atmospheric systems that can cause extreme events, and which may be reflected in heavy rainfall, floods, or drought episodes. Therefore, the research chose to investigate the years 1983 and 1984, rainy and dry standard-years respectively in the study area, where rainfall was described and spatialized through the geostatistical method of kriging at the monthly level and the rhythmic analysis technique was applied in order to identify what weather types are usual and extreme in the area. The results indicate that a high involvement of the frontal system in the year 1983 was responsible for the episodes of greater rainfall and peak water flow, especially in stationary front episodes. The year 1984 presented low rainfall in summer, a meteorological drought during the year, and the predominance of tropical air masses in relation to the frontal systems. The comparison between the two extreme years, a wet and a dry one, made it possible to understand the frequency and the chaining of the atmospheric systems during this period for the Alto Pardo watershed.