Characteristic mode model of tropical Pacific Ocean and dynamic mechanism of El Nino

In this paper, the tropical Pacific layer model of characteristic modes was developed, which improves and perfects the first vertical baroclinic mode model currently used in ENSO dynamic studies.The dynamic mechanisms and structures of tropical Pacific thermoclinic depth disturbances were further detected.These studies demonstrate that, in addition to the momentum exchange between oceanic mixed layer (surface layer) and thermoclinic layer (subsurface layer) which is an important dynamic mechanism triggering the thermoclinic depth disturbances, the vertical sea water mass exchange between oceanic layers plays an important dynamic role in triggering thermoclinic depth disturbances.Both kinds of physical processes excit different kind of dynamic modes and exhibit different structures, respectively.The disturbances induced by both kinds of dynamic modes intensify each other.The dynamic mechanism and dynamic processes of El Nino developing are also discussed in the paper.