Extreme rainfall events in the state of Rio Grande do Sul, Brazil, between 2004 and 2013. Part 2: synoptic characteristics of the persistent events

Abstract In this second part of the study about persistent rainfall events, the atmospheric conditions associated with these events are evaluated. Composites of diagnostic fields are presented for events classified by their duration. These composites showed that atmospheric systems with slow movement allow the permanence of areas of moisture flux convergence, heat transport and upward movement over the state of Rio Grande do Sul for several days. The moisture flux convergence vertically integrated proved to be a good tool to inference of the importance of events. The diagnostic fields did not show previously the duration of a rainfall event, as well as did not clearly demonstrate the major frequency of high rainfall accumulates in half east of the state of Rio Grande do Sul.