The Storm Tracks Response to Changes in Atmospheric Greenhouse Gas Concentration at the South of Brazil and Southwest Atlantic Ocean

Abstract

Here we investigate the ocean-atmosphere coupling and the contribution of the Sea Surface Temperature (SST) variations in: 1) Brazil-Malvinas Confluence (BMC) region, 2) Southwest Atlantic Ocean and 3) Southern Brazil. Numerical simulations of the ECHAM5/MPI-OM coupled ocean-atmosphere model were used to analyze the changes in the seasonal trajectory of the extratropical cyclones, in terms of intensification of physical mechanisms and implications for future scenarios. The numerical experiment for the future scenario considered an atmospheric CO 2 concentration of approximately 770 ppm, which represents an increment of more than 350 ppm over the current values recorded by the Mauna Loa reference station. For this scenario, the results indicated a Storm Tracks (ST) displacement of 5˚ latitude toward south and changes of the meridional transport of sensible heat, close to 50˚S. The increase in SST induces ST intensification and consequently an increase in the occurrence of extratropical cyclones. Overall, in the BMC region, we found a change in the pattern of cyclogenetic activity occurrence, with less frequent, but more intense events. On the Southern Brazilian region, the results of this study indicate increases in rainfall during summer months, whereas, a decrease in frequency and an increase in intensity were found for wintertime. We suggest that these changes could impact the climate dynamic of the Brazilian South coast, with a magnitude yet unknown.

The Surface Wind Influence on the Heat Fluxes Variability on the South Atlantic

“…4). According to Freitas et al (2019), regions with strong SST gradients, for example, BMC, provide higher SHF values, which may be associated with the greater baroclinity of the atmosphere over SW-SSA, and thus favoring so that the highest values can occur during JJA period (Fig. 4).…”

“…According to Acevedo et al (2010), turbulent flux of latent and sensitive heat are one of the ways in which energy is exchanged between the ocean and the atmosphere. Therefore, their correct determination on the oceans is decisive to understand the effects of ocean-atmosphere interactions on the climate (Yu et al 2011;Pezzi et al 2005Pezzi et al , 2016Freitas et al 2019;Leyba et al 2019). The heat exchange components between ocean and atmosphere include short and long-wave radioactive fluxes, LHF, and sensible heat flux (SHF).…”

Influência do efeito antropogênico nos padrões dominantes de atuação dos ciclones extratropicais no Hemisfério Sul

“…As faixas predominantes de atuação dos ciclones extratropicais, conhecidas como "Storm Tracks" (ST) desempenham um papel dominante na circulação atmosférica global. Sendo responsáveis pela redistribuição de calor entre equador e os polos, os ST exercem forte influência na radiação incidente, precipitação e cobertura de nuvens através dos processos de troca de calor, momentum e vapor d'água (Freitas et al, 2019;LAU, 1988;TING;HELD, 1990;Machado et al, 2021).…”

“…De acordo com Lehmann et al (2014), às mudanças climáticas projetadas tem grande potencial de afetar os padrões dominantes de atuação dos ST associados a mudanças no transporte de energia, momentum de vapor d'água. Freitas et al (2019), mostraram através de um experimento numérico para o cenário futuro considerando uma concentração de CO2 atmosférico de aproximadamente 770 ppm (partes por milhão) um deslocamento de Storm Tracks (ST) de 5 ° latitude em direção ao sul e mudanças do transporte meridional de calor sensível, próximo a 50 °S induzidos pelo aumento da SST intensificando a região de ST e consequentemente gerando aumento na ocorrência de ciclones extratropicais. De maneira geral, os resultados indicam mudança no padrão de ocorrência da atividade ciclogenética, com eventos menos frequentes, porém mais intensos.…”