A numerical investigation of the local ocean response to westerly wind burst forcing in the western equatorial Pacific

Numerical simulations of the local equatorial ocean response to idealized w esterly wind burst (WWB) forcing are described. In particular, the authors examine the development and evolution of the subsurface westward jet (SSWJ) that has been observed to accompany these wind events. This westward curre nt is interpreted as the signature of equatorial waves that accompany the d ownwelling and upwelling that occurs along the edges of the wind forcing re gion. Some important Features of the SSWJ include maximum intensity toward the eastern edge of the forcing region, a time lag between the wind Forcing and peak SSWJ development, and an eastward spreading of the SSWJ with time . The effect of wind burst zonal profile, magnitude, duration, and fetch on the SSWJ are explored. The response of an initially resting ocean to WWB f orcing is compared with that for model oceans that are spun up with annual- mean surface fluxes and monthly varying fluxes. It is demonstrated that the gross features of the response for the spun up simulations can he well app roximated by adding the background zonal current structure prior to the int roduction of the wind burst to the initially resting ocean current response to the WWB. This result suggests that the zonal current structure that is present prior to the commencement of WWB forcing plays a key role in determ ining whether or not a SSWJ will develop.