Sea‐surface temperature co‐variability in the Southern Atlantic and Indian Oceans and its connections with the atmospheric circulation in the Southern Hemisphere

Abstract

The relationship between sea-surface temperature (SST) inter-annual variability at the subtropical and midlatitudes of the southern Atlantic and Indian Oceans and its links with the atmospheric circulation in the Southern Hemisphere are investigated over the 1950-1999 period. Exploratory analysis using singular value decomposition and further investigations based on simple indices show that a large part of regional SST variability is common between the southwestern parts of both basins at subtropical and midlatitudes during the austral summer. Interestingly, these areas are also significantly associated with the far southwestern Pacific (Tasman Sea area). The patterns and time series of covariability between the southern Atlantic and Indian Oceans are shown to correspond to SST modes previously described in the literature as 'subtropical dipoles', independently for the Atlantic and Indian Oceans. Composite analyses show that austral summers characterized by simultaneous warm (and to a lesser extent cold) SST anomalies in the southwestern (northern) part of both southern oceans are related to atmospheric anomalies mainly involving a southward shift and a strengthening of the subtropical high-pressure systems over both basins. These anomalies are embedded in a hemispheric signal associating two cores of positive pressure anomalies within the South Pacific anticyclone. The global picture appears to have a wave number 4 spatial structure. The associated low-level wind and latent heat-flux anomalies and the lags between atmospheric variables and SST anomalies are consistent with an atmospheric forcing on the ocean. Potential links of these patterns with large-scale modes of climate variability in the Southern Hemisphere are discussed.

Validation of a coupled GCM and projection of summer rainfall change over South Africa, using a statistical downscaling method

“…The explained variances are 21.2 and 19.8%, respectively. These patterns broadly coincide with those depicted in Fauchereau et al (2003). They exhibit a pressure distribution over the Atlantic Ocean which is similar to that of the Indian Ocean, including anomalies of opposite signs between the tropical and the subtropical-temperate latitudes.…”

“…Monthly mean sea-level pressure (SLP), which is used as the independent variable in the statistical downscaling model, is from NCAR/NCEP reanalysis data for 1948 to 1999 (Kalnay et al 1996). NCEP SLP has been shown to be close to the GMSLP (Global Mean Sea Level Pressure) observed data from the Hadley Centre (Fauchereau et al 2003). In addition, we also use gridpoint precipitation and SLP data from the GCM.…”

Role of Tropical SST Variability on the Formation of Subtropical Dipoles

“…Behera and Yamagata (2001) first identified 57 this phenomenon in the southern Indian Ocean. Since then, several studies have shown the 58 existence of subtropical dipoles in the South Atlantic (Fauchereau et al 2003) and South 59…”

Climate change, food security, and livelihoods in sub-Saharan Africa

“…Beyond increases in temperature, climate change in sub-Saharan Africa is expected to cause changes in rainfall intensity (Thomas et al 2007;Songok et al 2011a), increases in the incidence of extreme events such as droughts and floods (Richard et al 2001;Fauchereau et al 2003;New et al 2006;Niang et al 2014;Tschakert et al 2010), increases in desertification (Reich et al 2001), and alterations in certain disease vectors causing changes in the spatial and temporal transmission of infectious diseases (Hay et al 2002;Chen et al 2006). Expected impacts include shortened or disrupted growing seasons, reductions in the area suitable for agriculture, and declines in agricultural yields in many regions of subSaharan Africa (Niang et al 2014;Müller et al 2011;Sarr 2012).…”