Tropical Atlantic Contributions to Strong Rainfall Variability Along the Northeast Brazilian Coast

Abstract

Tropical Atlantic (TA) Ocean-atmosphere interactions and their contributions to strong variability of rainfall along the Northeast Brazilian (NEB) coast were investigated for the years 1974–2008. The core rainy seasons of March-April and June-July were identified for Fortaleza (northern NEB; NNEB) and Recife (eastern NEB; ENEB), respectively. Lagged linear regressions between sea surface temperature (SST) and pseudo wind stress (PWS) anomalies over the entire TA and strong rainfall anomalies at Fortaleza and Recife show that the rainfall variability of these regions is differentially influenced by the dynamics of the TA. When the Intertropical Convergence Zone is abnormally displaced southward a few months prior to the NNEB rainy season, the associated meridional mode increases humidity and precipitation during the rainy season. Additionally, this study shows predictive effect of SST, meridional PWS, and barrier layer thickness, in the Northwestern equatorial Atlantic, on the NNEB rainfall. The dynamical influence of the TA on the June-July ENEB rainfall variability shows a northwestward-propagating area of strong, positively correlated SST from the southeastern TA to the southwestern Atlantic warm pool (SAWP) offshore of Brazil. Our results also show predictive effect of SST, zonal PWS, and mixed layer depth, in the SAWP, on the ENEB rainfall.

A further analysis of the tropical Atlantic SST modes and their relations to north‐eastern Brazil rainfall during different phases of Atlantic Multidecadal Oscillation

“…Rainfall variability due to the other systems such as the easterly wave disturbances (EWs) and upper tropospheric cyclonic vortices (TCVs) is out of the scope of the present analysis. The EWs affect eastern NEB during austral winter (Yamazaki and Rao, 1977;Kouadio et al, 2012;Hounsou-Gbo et al, 2015) and the TCVs are more common during austral summer and affect most of NEB (Kousky and Gan, 1981).…”

Impacts of the Madden‐Julian oscillation on intraseasonal precipitation over Northeast Brazil

“…When these disturbances propagate toward the eastern NEB they can generate large rainfall amounts specially over the eastern coastal areas (e.g. Gomes et al, 2015;Hounsou-gbo et al, 2015;Kouadio et al, 2012). Rao et al (1993) found that the seasonal variation of the intensity and position of the subtropical high in the South Atlantic Ocean modulates coastal winds during the fall and winter.…”

PIRATA: A Sustained Observing System for Tropical Atlantic Climate Research and Forecasting

“…These climate modes are of importance especially due to their impact on precipitation over the adjacent continents. Variations in rainfall over Northeast Brazil are closely related to SST variability in the tropical Atlantic Ocean (e.g., Hounsou-Gbo et al, 2015). In particular SST variability in the ACT is related to the West African Monsoon (Brandt, Caniaux, et al, 2011;Caniaux et al, 2011), and Benguela Niños have an impact on rainfall over southwestern Africa and coastal central Africa (Lutz et al, 2015;Reason & Rouault, 2006;Rouault et al, 2009).…”