Extended Abstract (68K)13C.5
Collective and competitive roles out of thermocline and zonal advective feedbacks in the ENSO Mode
Soon-Il An, University of Hawaii at Manoa, Honolulu, HI; and F. F. Jin
Using a version of a recharge oscillator model for ENSO, it is demonstrated that two essential feedbacks for the El Nino: the vertical advection of anomalous subsurface temperature by the mean upwelling (Thermocline feedback) and the zonal advection of mean sea surface temperature (SST) by anomalous current (Zonal advective feedback), which are linked dynamically through the geostrophic approximation, tend constructively to contribute to the growth and phase transition of the ENSO. However, these two feedbacks control the leading coupled mode in different ways. The thermocline feedback leads to a coupled mode through the merging of the damped SST mode and ocean adjustment mode, whereas the zonal advective feedback tends to destabilize the gravest ocean basin mode. It is also shown that the observed interdecadal climate shift can effectively modify the strength of these two major coupled feedbacks. These modifications lead to quantitative changes of the leading coupled mode in its frequency, growth rate, and spatial pattern, which are consistent with the observation.
Session 13C, Ocean Atmosphere Interaction II (Parallel with Sessions 13A, 13B, and 13D)
Thursday, 2 May 2002, 11:00 AM-12:30 PM
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