HR: 0800h
AN: GC51A-0166    [Abstracts]
TI: On the predictability and dynamics of westerly wind bursts in the equatorial Pacific
AU: * Tziperman, E
EM: eli@eps.harvard.edu
AF: Harvard University, 20 Oxford St, Cambridge, MA 02138, United States
AU: Kuang, Z
EM: kuang@fas.harvard.edu
AF: Harvard University, 20 Oxford St, Cambridge, MA 02138, United States
AU: Huybers, P
EM: phuybers@fas.harvard.edu
AF: Harvard University, 20 Oxford St, Cambridge, MA 02138, United States
AU: Yu, L
EM: lyu@whoi.edu
AF: Woods Hole Oceanographic Institution, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Gebbie, G
EM: gebbie@eps.harvard.edu
AF: Harvard University, 20 Oxford St, Cambridge, MA 02138, United States
AB: Present-day ENSO's variability is strongly affected by westerly wind bursts (WWBs) in the equatorial Pacific. Because of their short time scale, the seemingly stochastic WWBs were thought to be purely external to the equatorial Pacific system. However, more recent analysis shows that these events are, in fact, strongly modulated by the large scale SST, and ENSO in particular. Thus these events seem a part of the ENSO cycle rather than external forcing and it is important to understand their relation to ENSO in order to be able to understand both future and past ENSO's behavior and its dependence on the general climate state. Although the WWB wind stress at a given location is not well correlated linearly with the SST, the characteristics of WWBs, such as duration, wind strength, location, fetch, and probability of occurrence, are well described as a linear function of SST. A prognostic WWB model is developed using a multiple linear regression to a record of satellite-derived winds. Given the observed large-scale tropical Pacific SST, the model reproduces the majority of observed variance in seven designated WWB characteristics and it shows the potential to be used for prediction purposes. In order to further understand the dynamics of these WWBs, we use the analysis of wind and OLR observations as well as linear and nonlinear shallow water atmospheric model to investigate the link between tropical atmospheric convection and westerly wind bursts. It is found that convection may force the observed westerly wind burst signal, but that the momentum dynamics of these wind bursts may involve more than the linear Gill- type atmospheric model equations.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 3374 Tropical meteorology
DE: 4231 Equatorial oceanography
DE: 4922 El Nino (4522)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting