Figure 1

Tropical Atlantic climatology. Mean climatological sea surface temperature (SST) (°C) and 850 hPa wind field (m/s) over the tropical Atlantic Basin for (A) March, April and May (MAM) and (B) June, July and August (JJA). Both fields are averaged over the period 1982–2016. Contour interval for SST (white lines) is 1 °C. SST data are based on NOAA Optimum Interpolation SST V2⁵⁵, and wind field is from ERA-Interim reanalysis data⁵⁶. ITCZ plots are based on maximum mm.day⁻¹ in MAM and JJA⁵⁷. (C) Cross-equatorial and trans-hemispheric co-variance between precipitation in NEB Brazil and West Africa due to tropical South Atlantic SST variability represented by the correlation between Tropical South Atlantic (TSA) SST index (SST averaged over 0–20 S, 10E–30 W (blue box), calculated from HadISST and NOAA OI data sets^9,58 with CRU TS3.24 precipitation data⁵⁹. Correlations are for respective rainy seasons (MAM in South America and JJA in Africa) over period 1948–2014. White contour lines indicate regions with correlations significant at p < 0.05. Study sites: (1) Boqueirão Lake and Ceará-Mirim IAEA Station; (2) Fortaleza Station; (3) Cariaco Basin¹⁴.