Abstract
Despite similar evolution of Niño3.4 index for three strong El Niño events in the tropical Pacific in 1982–1983, 1997–1998 and 2015–2016, divergent sea surface temperature anomalies (SSTAs) were observed in the North Atlantic (NA) in spring following El Niño peak. Strong teleconnection occurred for the first two events in 1982–1983 and 1997–1998, leading to a negative phase of a North Atlantic Oscillation-like circulation over the extratropical NA, and thus a positive tripolar SSTA pattern in the NA. But the teleconnection was weak for the case of 2015–2016 El Niño, the SSTA in spring 2016 in NA being mainly created and maintained by the preconditioning of the NA basin and local atmosphere-ocean interactions. The salient difference among the three events resides in their ways to operate the teleconnection linking the central-eastern equatorial Pacific and the subtropical eastern North Pacific to the extratropical NA, which would be a key to explain the different impacts of the three exceptional El Niño events. It is furthermore shown that the reduced anomalous westerlies over Central America along 30° N around the peak time of 2015–2016 El Niño play a role of inhibition for an efficient Rossby wave energy propagation from the tropics, eastward into the Gulf of Mexico and northward into midlatitudes in the western NA.
Highlights
The El Niño-Southern Oscillation (ENSO) is an important interannual variability component of the climate system
Characteristics of spring North Atlantic (NA) sea surface temperature anomalies (SSTAs) Let us take a closer look at how El Niños and NA SSTA evolved for the 1982–1983, 1997–1998 and 2015–2016 El Niño events
During the 1982–1983 event, the NA index was negative in the El Niño developing and peak phases, and became robustly positive after the El Niño peak, with the SSTA index maximizing in April (1.1 ◦C)
Summary
The El Niño-Southern Oscillation (ENSO) is an important interannual variability component of the climate system It typically develops during boreal spring and summer, peaks in winter in the equatorial central-eastern Pacific, and decays in the following spring and summer. Accompanying ENSO, positive sea surface temperature anomalies (SSTAs) generally occur over the tropical North Atlantic (NA), with a tripolar structure for the whole North Atlantic basin. Such SST anomalies in NA can exert important impacts on the regional climate (Rodwell et al 1999, Czaja and Frankignoul 2002, Li and Conil 2003, Msadek et al 2011, Wang et al 2009). A few hypotheses can be found in literature to explain the linkage
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