Variability of the Atlantic Niño: Impacts on precipitation in the state of Maranhão, Brazil

Abstract

The study analyzed the influence of the Atlantic Niño on precipitation anomalies in Maranhão from 1980 to 2020. Using the Atlantic Niño index, 20 events were identified, predominantly with 2- to 8-year scales. A significant reduction was noted from the 2000s, likely due to the weakening of the Bjerknes feedback and the Atlantic Multidecadal Oscillation. However, events in 2019 and 2021 suggested that the negative phase of the Atlantic Multidecadal Oscillation may have contributed to the reactivation of the Atlantic Niño after 19 inactive years. The negative early termination event was “non-canonical”, with positive sea surface temperature anomalies in the North Tropical Atlantic and positive east winds. A relationship was found between the Atlantic Niño and the Atlantic Meridional Mode, influencing elements like sea surface temperature and interhemispheric winds, which in turn affected precipitation patterns in Maranhão. These findings highlight the complex climate interactions in the region, emphasizing the need to consider multiple factors, including local and remote climate modes, for understanding precipitation variability. The study underscores the importance of continuous monitoring and research on the Atlantic Niño and the Atlantic Meridional Mode to anticipate impacts on rainfall volume and distribution in Maranhão, aiding regional strategic planning.