Observations and wind-forced model simulations of the mean seasonal cycle in tropical Pacific sea surface topography

We examine simulations of the mean seasonal cycle in the tropical Pacific using a multiple vertical mode linear numerical model forced with three different surface wind stress products average over the period 1979-1981. The model is run to equilibrium for each four vertical modes, and results are summed. Simulated mean seasonal cycles in dynamic height and sea level are then compared with observed variations based on expendable bathythermograph and island tide gauge data averaged over the same 1979-1981 period. All simulations show characteristic features of the mean meridional ridge-through structure in surface topography. However, north and south equatorial ridges at 20°N and 20°S are much higher than those observed, only weak equatorial ridges are generated near 4°N, and none of the simulations exhibits a significant equatorial trough. These discrepancies are due principally to limitations in model physics in the wind forcing. Observed and modeled mean seasonal variations in surface height are of the order of a few centimeters