Abstract This study analyzed the influence of strong and moderate El Niño-Southern Oscillation (ENSO) events on the seasonal and interannual variabilities of the sea surface temperature (SST) in the Western Equatorial Atlantic (WEA) Ocean and how the precipitation over the state of Maranhão, in Brazil, responds to the zonal teleconnection. To evaluate the ENSO magnitude and phase in the four Niño regions (1+2, 3, 3.4, and 4), the SODA 3.3.1 oceanic reanalysis database for the period from 1980 to 2015 was used. Our results showed that the La Niña phase with moderate magnitude was the most predominant among the 70 events analyzed, with Niño 3.4 presenting the highest number (20) of ENSO events (both positive and negative phases). At lag = 0, we found that significant negative correlations prevailed between the WEA SST anomalies and ENSO index, with the region of Niño 3.4 showing the most significant correlations (r = −0.25). The whole events of El Niño and La Niña were, respectively, accompanied by a cooling and a heating of up to −0.6°C or +0.8°C in the WEA Ocean. The WEA SST anomalies during El Niño and La Niña events have, respectively, reduced and increased the precipitation in Maranhão around ± 100 mm in a quarter. Strong El Niño events influence a greater precipitation deficit in Maranhão than moderate El Niño events. Moderate La Niña events have more pronounced influence on the precipitation over Maranhão than strong La Niña events do, especially on the negative anomalies. Our results showed that the central, northern, and eastern tip sectors of the state are the most affected by this zonal teleconnection. We concluded that ENSO’s significant influences on the WEA SST seasonal variability, added to the performance of the Atlantic Meridional Mode (Soares, 2019), determine the quality of the rainy season (March–April–May) in the state of Maranhão.

Resumo O objetivo deste estudo é investigar a precipitação pluvial e os ventos no Brasil associados ao anticiclone subtropical do Atlântico Sul (ASAS) nas diferentes fases do Modo Anular Sul (SAM). Na fase positiva (negativa) do SAM, o ASAS está posicionado anomalamente para sul (norte), assim como a Zona de Convergência Intertropical, contribuindo com aumento (redução) da precipitação pluvial na Região Norte (Norte e Nordeste). Assim, ventos mais intensos (fracos) são observados em algumas áreas no sul da Região Nordeste, Sudeste e sul da Região Sul (grande parte da Região Nordeste e parte do Tocantins e Minas Gerais) no outono e inverno (outono). Em relação à precipitação pluvial, há redução (aumento) no centro-sul (sul da Região Sul/ centro-leste) do Brasil entre o inverno e verão (na primavera e outono/ verão). Na fase negativa do SAM existe uma redução na duração da estação chuvosa na região tropical associada a um enfraquecimento da atividade da Zona de Convergência do Atlântico Sul e da convecção tropical. O outono é a única estação em que o fortalecimento dos ventos na Região Nordeste pode ser utilizado para complementar a produção de energia elétrica por fonte hidráulica devido ao déficit de precipitação pluvial em ambas as fases do SAM.

Abstract The objective of this study is to investigate the precipitation and winds in Brazil associated with the South Atlantic subtropical anticyclone (SASA) in the different phases of the Southern Annular Mode (SAM). During the positive (negative) phase of the SAM, the SASA is positioned anomalously to the south (north), as well as the Intertropical Convergence Zone, contributing to the increase (reduction) of precipitation in the North (North and Northeast) region. Thus, we observed more intense (weak) winds in some areas of the south-Northeast, Southeast, and southern South -regions (much of the Northeast region and part of Tocantins and Minas Gerais) in the fall and winter (fall). Regarding precipitation, there is a reduction (increase) in south-central (southern-South region/ central-eastern) of Brazil between winter and summer (in spring and autumn/ summer). During the negative phase of the SAM, there is a reduction in the duration of the rainy season in the tropical region associated with a weakening of activity in the South Atlantic Convergence Zone and tropical convection. Autumn is the only season in which the strengthening of winds in the Northeast region can be used to complement hydroelectric power production due to precipitation deficit in both SAM phases.

Resumo Como a borda do gelo marinho antártico está localizada em uma região muito sensível, sob a Frente Polar Antártica, existe um grande potencial da variabilidade do gelo marinho afetar a circulação atmosférica. Assim, o objetivo deste estudo foi investigar as possíveis relações entre os eventos extremos de gelo marinho antártico e as células de circulação meridional no Pacífico Sudeste, região onde há intensa variabilidade em várias escalas de tempo. Os resultados mostram que quando há eventos extremos de expansão de gelo marinho no setor do mar de Ross, existe um resfriamento da TSM, que resulta em uma atmosfera adjacente fria, aumentando os gradientes térmicos entre a borda do gelo marinho e a região de mar aberto. Os gradientes de pressão são fortalecidos, fortalecendo o cinturão circumpolar de baixas pressões e o jato polar. Assim, existe um fortalecimento do ramo ascendente da célula de Ferrel sobre o Oceano Austral, enquanto há enfraquecimento nas latitudes médias, por conservação de massa. Observamos o padrão oposto em eventos extremos de retração de gelo marinho no setor do mar de Ross e expansão no setor do mar de Weddell.

Abstract Because the Antarctic sea ice edge is located in a region quite sensible, under the Antarctic Polar Front, there is a great potential of sea ice variability to affect the atmospheric circulation. The objective of this study was to investigate possible relationships between the extreme events of Antarctic sea ice and the cells of meridional circulation over the Southeastern Pacific, where there is intense climate variability on various time scales. The results show that when there are extreme events of sea ice expansion in the Ross Sea sector there is cooling of the SST, which results in the surrounding atmosphere cools, increasing the thermal gradient between the edge of sea ice and the open water region. The southern pressure gradients are strengthened, which strengthens the circumpolar low pressure belt and the polar jet. So there is a strengthening of the ascending branch of the Ferrel cell over the Southern Ocean while there is a weakening in midlatitudes via conservation of mass. We observe the opposite pattern in extreme events of sea ice decrease in the Ross Sea sector and expansion in the Weddell Sea sector.