How the two nodes of the tropical Atlantic sea surface temperature dipole relate the climate of the surrounding regions during austral autumn

Abstract

The relations of both nodes of the tropical Atlantic (TA) cross‐equatorial sea surface temperature (SST) gradient (GRAD) mode to the climate of northeast Brazil (NEB) during the 1901–2012 period are examined separately. The GRAD mode consists of a SST anomalous pattern anti‐symmetric about the equator with centres in the region of the northeasterly and southwesterly trade winds. The positive GRAD (PGRAD) (negative GRAD [NGRAD]) modes defined by their northern or southern nodes are considered separately, as well as, if they are preceded or not by an El Niño (EN) (a La Niña, LN). The PGRAD mode defined by the northern (southern) node and preceded by an EN is indicated by PGRAD_TNA_EN (PGRAD_TSA_EN), and that not preceded by an EN is indicated by PGRAD_TNA (PGRAD_TSA). The corresponding NGRAD modes are indicated by NGRAD_TNA_LN, NGRAD_TSA_LN, NGRAD_TNA and NGRAD_TSA. Our analysis is limited to the NEB rainy season (March–May), when the GRAD mode is more pronounced and the NEB rainfall is more closely related to the TA SST variations. In general, the South Atlantic subtropical high is crucial in defining the cross‐equatorial flow, responsible for the anomalous meridional positioning of the Atlantic inter‐tropical convergence zone. When a positive (negative) dipole‐like SST anomaly pattern is established in the TA, the negative (positive) rainfall anomalies occupy most of NEB. This is the case of the PGRAD_TSA_EN, PGRAD_TNA, NGRAD_TSA_LN and NGRAD_TNA_LN. Most of the GRAD modes defined by TNA are also related to the El Niño‐Southern Oscillation (ENSO), in such a way that an EN (a LN) precedes a PGRAD (NGRAD) event, and most of the GRAD modes defined by TSA do not depend on the ENSO. Also, the PGRAD events are well distributed during both Atlantic multidecadal oscillation phases and the NGRAD events occur preferably during its cold phase.

The influence of the Atlantic multidecadal oscillation on the eastern Andes low-level jet and precipitation in South America

“…The AMO manifests itself as an internal mode of sea surface temperature (SST) variability such that positive phases are associated with warming in the North Atlantic and cooling in the equatorial Atlantic. 21 Important linkages have been found between the AMO and seasonal climate variability over northeast Brazil 20,22,23 , as well as over southern South America. 24 Here, we show that the AMO has a remarkable control on decadal-tomultidecadal variability of the SALLJ.…”

El Niño–Southern Oscillation related teleconnections over South America under distinct Atlantic Multidecadal Oscillation and Pacific Interdecadal Oscillation backgrounds: La Niña

“…In this case, a southwards GRAD mode is established in the tropical Atlantic in all seasons. Several authors have shown that the combined action of a southwards GRAD mode in the tropical Atlantic and LN results in an anomalous wetness over NEB during the austral autumn (Pezzi and Cavalcanti, ; Kayano et al ., , among others).…”

Copula-Based Multivariate Frequency Analysis of the 2012–2018 Drought in Northeast Brazil

“…The Atlantic Ocean also has its low-frequency variability mode, referred to as Atlantic Multidecadal Oscillation (AMO) [51,52]. Linkages between AMO and seasonal climate variability over NNEB have also been found [53][54][55][56][57]. Periods with simultaneously positive (or negative) PDO and AMO phases result in a more predictable behavior of rainfall in the region, with values below (or above) than normally expected [58].…”