Effects of atmospheric systems operating in the Northeast of Brazil on the volumes of artificial reservoirs

Abstract This study aims to quantify the impact of rainfall patterns influenced by the seasonal movement of the Intertropical Convergence Zone (ITCZ) southward, Frontal Systems (FS), and South Atlantic Convergence Zone (SACZ) during El Niño, La Niña, and neutral years on water volumes in artificial reservoirs across the Northeast of Brazil (NEB) from 1998 to 2018. Data sources include outgoing longwave radiation from NOAA, daily rainfall from the Global Precipitation Climatology Project, and reservoir volume from the National Water Agency and state departments. ITCZ identification employed semi-objective techniques, while CPTEC/INPE reports aided in identifying ITCZ and SACZ. The study calculated reservoir water volume percentages and applied correspondence analysis between volume changes and atmospheric systems during El Niño, La Niña, and neutral years. Typically, the ITCZ central position during February-May hovered around − 1ºS; when deviated, negative rainfall anomalies occurred, correlating with reduced reservoir volumes. El Niño years consistently exhibited negative rainfall anomalies with the ITCZ between − 1ºS and 1ºN. Approximately 17% of FS reaching Brazil during November-February reached southern NEB, with an average of three FS and SACZ cases per season in this region. Lower FS and SACZ occurrences during November-February often corresponded with negative reservoir volume trends.