Revisiting remote drivers of the 2014 drought in South-Eastern Brazil

Abstract

South-Eastern Brazil experienced a devastating drought associated with significant agricultural losses in austral summer 2014. The drought was linked to the development of a quasi-stationary anticyclone in the South Atlantic in early 2014 that affected local precipitation patterns over South-East Brazil. Previous studies have suggested that the unusual blocking was triggered by tropical Pacific sea surface temperature (SST) anomalies and, more recently, by convection over the Indian Ocean related to the Madden–Julian Oscillation. Further investigation of the proposed teleconnections appears crucial for anticipating future economic impacts. In this study, we use numerical experiments with an idealized atmospheric general circulation model forced with the observed 2013/2014 SST anomalies in different ocean basins to understand the dominant mechanism that initiated the 2014 South Atlantic anticyclonic anomaly. We show that a forcing with global 2013/2014 SST anomalies enhances the chance for the occurrence of positive geopotential height anomalies in the South Atlantic. However, further sensitivity experiments with SST forcings in separate ocean basins suggest that neither the Indian Ocean nor tropical Pacific SST anomalies alone have contributed significantly to the anomalous atmospheric circulation that led to the 2014 South-East Brazil drought. The model study rather points to an important role of remote forcing from the South Pacific, local South Atlantic SSTs, and internal atmospheric variability in driving the persistent blocking over the South Atlantic.

Drought Assessment in São Francisco River Basin, Brazil: Characterization through SPI and Associated Anomalous Climate Patterns

“…The results obtained through the SPI-12 analysis are in accordance with the ones obtained via different methodologies for the NEB [14,15,22,23]. Droughts were also detected in the SEB during the middle 2010s [25,26,53,54].…”

“…The authors revealed, between 1980 and 2015, a drying trend in the midand southern regions of the SFRB. In the SEB, dry periods have been extensively reported since the late 1990s [25,26], and according to Geirinhas et al [27], the states of Minas Gerais, São Paulo, and Rio de Janeiro recorded statistically significant increases in the number of episodes of summer droughts and heat waves between 1980 and 2018.…”

“…The severe drought of 2014/2015, for instance, was associated with an anomalous convective activity in the region of Australia that triggered the action of an anomalous high atmospheric pressure system over the warmer South Atlantic Ocean. This pattern led to the frontal systems having more oceanic trajectories and disfavored the formation of South Atlantic Convergence Zone (SACZ) events, which, together with local convection, is the main system causing rain in the SEB [25,26,53,54].…”

Summer dry events on synoptic and intraseasonal timescales in the Southeast Region of Brazil

“…Rodrigues et al (2019) demonstrate that this pattern is mainly due to the increased incident shortwave radiation and negative anomalies of latent heat flux (from the ocean to the atmosphere). Results of numerical simulations from Finke et al (2020) suggest that these positive SST anomalies contribute to the establishment of a high south of SEB and then favouring the dry periods over SEB.…”

Padrões Climatológicos Associados a Eventos De Seca No Leste Do Estado De São Paulo

“…A seca no leste de SP causa sérios problemas relacionados ao abastecimento e distribuição de água, pois é a região mais densamente povoada do estado, e inclui a capital (com mais de 20 milhões de habitantes em sua região metropolitana) e importantes reservatórios hídricos. Um recente episódio de seca muito intenso em 2014/2015 teve forte impacto sócio-econômico sobre o leste de SP, e foi atribuído em parte a uma teleconexão com a TSM da bacia do oceano Pacífico, via propagação de ondas de Rossby (Nobre et al, 2016;Coelho et al, 2016, Finke et al, 2020.…”