Analyzing Heat Wave Frequency in Brazil (1991-2020): Study Across Diverse Climates Using the Warm Spell Duration Index

Keywords: WSDI, Brazilian climate patterns, Temperature trends, Regional heatwave frequency
Abstract Type: Paper Abstract

Abstract

Heat waves are extreme weather events that can have significant impacts due to high and prolonged temperatures. In Brazil, the geographic and atmospherical aspects create a variety of eight climate patterns. This study analyzed the frequency of heat waves during the most recent climatological reference period (1991-2020) across these regions. The Warm Spell Duration Index (WSDI) was the methodology used to measure the frequency of heat waves. Maximum temperature data above the 90th percentile, sustained for six consecutive days. The study focused on the cities of São Gabriel/AM, Manaus/AM, Recife/PE, Brasília/DF, Petrolina/PE, Porto Alegre/RS, Santa Vitória do Palmar/RS, and Viçosa/MG. Records from nearby automatic weather stations within the same climate type filled gaps in historical data. Descriptive statistical analyses were conducted, including total count, percentage, and trend analyses of heat wave events. Findings showed that from the start of the series, the last decade (2011-2020) recorded the highest percentage of heat waves—over 30% in all regions—compared to the two previous decades. Among the cities analyzed, Brasília, Recife, and Manaus experienced the most frequent heat waves, with 54 and 47 events, respectively, over the study period.