Modelling the Upper Ocean Dynamics during El Ni？o Modoki 2002-2003 off Peru

The dynamics of the upper ocean layer off Peru during El Ni？o Modoki 2002-2003 is investigated numerically using a vertically integrated $1\frac{1}{2}$ layer stabilized finite element model for the open and limited coastal ocean. The model solves the motion and continuity hydrodynamic equations coupled with the advection–diffusion transport equation for temperature. Solutions are forced by time dependent regional heat fluxes (short wave radiation and long wave back radiation) and wind data derived from the “European Centre for Medium-Range Weather Forecasts (ECMWF)”. The role of the regional wind and heat fluxes on the time dependent dynamics is evaluated. The problem investigated here is whether the regional forcings and the ocean hydro thermodynamical response in space and time are connected. Numerical solutions are found in an oceanic region between the equator and 30？S and between 70？W and 100？W. The model is successful in reproducing time dependent features of El Ni？o 2002-2003, such as the Sea Surface Temperature (SST) field, which compares favorably with observed patterns in terms of spatial distribution during the time evolution of El Ni？o. A Mean Absolute Error of 0.56？C is evaluated. Dynamically, the model results demonstrate that the SST field evolution during 2002-2003 is a causal effect of the regional forcings, mainly influenced by the heat fluxes. The results were possible due to a particular observed thermal feature of the study region: the rate of change of the Sea Surface Temperature and the net incident heat flux are linked during 2002-2003.