HR: 17:15h
AN: OS44A-06    [Abstracts]
TI: Modulation of Westerly Wind Burst Occurrence by Sea Surface Temperature as an Intrinsic Part of ENSO Dynamics
AU: * Gebbie, G A
EM: gebbie@eps.harvard.edu
AF: Harvard University, Dept. of Earth and Planetary Sciences 20 Oxford St., Cambridge, MA 02138 United States
AU: Eisenman, I
EM: eisenman@fas.harvard.edu
AF: Harvard University, Dept. of Earth and Planetary Sciences 20 Oxford St., Cambridge, MA 02138 United States
AU: Wittenberg, A T
EM: andrew.wittenberg@noaa.gov
AF: Geophysical Fluid Dynamics Laboratory, Sayre Hall, Princeton University, Princeton, NJ 08544 United States
AU: Tziperman, E
EM: eli@eps.harvard.edu
AF: Harvard University, Dept. of Earth and Planetary Sciences 20 Oxford St., Cambridge, MA 02138 United States
AB: Westerly wind bursts (WWBs), strong westerly gusts in the equatorial Pacific that occur a few times a year, excite ocean waves and are widely believed to be a key component of El Nino's onset mechanism. WWBs are normally considered an external stochastic forcing of ENSO. Recent observational syntheses suggest, however, that the occurrence and characteristics of WWBs depend upon the state of the equatorial Pacific SST. In particular, these events seem stronger and more common when the warm pool is extended eastward. To study the two-way interaction between ENSO and WWBs, a hybrid coupled model is used, based on the GFDL ocean model and an atmospheric model that is partitioned into a standard linear statistical model and a representation of WWB events. The model WWBs are best represented in a semi-stochastic way; their occurrence is not deterministic, but it does depend on the large-scale SST in a way motivated by observations. When WWBs are influenced by SST, the averaged ENSO amplitude is significantly larger than when WWBs are purely stochastic. The sensitivity of ENSO's period and amplitude to the details of WWB modulation is investigated, and the implications for ENSO predictability are also discussed.
DE: 3238 Prediction (3245, 4263)
DE: 3305 Climate change and variability (1616, 1635, 3309, 4215, 4513)
DE: 4263 Ocean predictability and prediction (3238)
DE: 4504 Air/sea interactions (0312, 3339)
DE: 4522 ENSO (4922)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005