On the response of the Equatorial Atmosphere and Ocean to changes in Sea Surface Temperature along the Path of the North Equatorial Counter Current

Abstract. The CESM climate model is used to test the hypothesis that the changes observed during El Niños are, at least in part, a response of the coupled ocean/atmosphere system to changes in sea surface temperature along the path of the North Equatorial Counter Current.

The model results show that increased temperatures at the latitudes of the NECC produce more deep atmospheric convection within the ITCZ. This has a local effect on the ocean's surface pressure field. The increased deep atmospheric convection also appears to affect the longitude structure of the Hadley Circulation. This results in less sinking air in the south-east Pacific and produces changes in surface pressure similar to those of a Southern Oscillation. Both mechanisms reduce the zonal component of the surface pressure gradient and wind stress along the Equator, and produce an El Niño type response in the ocean.