Linking the Pacific Meridional Mode to ENSO: Coupled Model Analysis

Abstract The occurrence of a boreal spring phenomenon referred to as the Pacific meridional model (MM) is shown to be intimately linked to the development of El NioSouthern Oscillation (ENSO) in a long simulation of a coupled model. The MM, characterized by an anomalous northsouth SST gradient and anomalous surface circulation in the northeasterly trade regime with maximum variance in boreal spring, is shown to be inherent to thermodynamic oceanatmosphere coupling in the intertropical convergence zone (ITCZ) latitude, and the MM existence is independent of ENSO. The thermodynamic coupling enhances the persistence of the anomalous winds in the deep tropics, forcing energetic equatorially trapped oceanic waves to occur in the central western Pacific, which in turn initiate an ENSO event. The majority of ENSO events in both nature and the coupled model are preceded by MM events.

Linking the Pacific Meridional Mode to ENSO: Coupled Model Analysis Academic Article