Contrasting the termination of moderate and extreme El Niño events in coupled general circulation models

Matthieu Lengaigne, Gabriel A. Vecchi
2009 Climate Dynamics  
An assessment of coupled IPCC-AR4 models indicates that the termination characteristics and mechanisms of observed El Niño events, involving meridional processes tied to the seasonal cycle, are present in climate models. This includes the processes that precondition the termination of El Niño events in general, and the mechanisms leading to a peculiar termination of extreme El Niño events (such as those of 1982-3 and 1997-8), in which the eastern equatorial Pacific warm Sea Surface Temperature
more » ... nomalies (SSTA) persist well into boreal spring/early-summer. The mechanisms controlling the peculiar termination of extreme El Niño events, related to the development of an equatorially-centred intertropical convergence zone, are consistent across the four models that exhibit extreme El Niño events and observational record, suggesting that this peculiar termination represents a general feature of extreme El Niño events. Further, due to their unusual termination, extreme El Niño events exhibit an apparent eastward propagation of their SSTA, which can strongly influence estimates of the apparent propagation of ENSO over multidecadal periods. Interpreting these propagation changes as evidence of changes in the underlying dynamical feedbacks behind El Niño could therefore be misleading, given the strong influence of a single extreme event.
doi:10.1007/s00382-009-0562-3 fatcat:pjgpr53t65ebxnmyic72j6d5ym