CLIMATOLOGY AND INTERANNUAL VARIABILITY SIMULATED BY THE ARPEGE-OPA COUPLED MODEL

A 10-year simulation with a coupled ocean-atmosphere general circulati on model (CGCM) is presented. The model consists of the climate versio n of the Meteo-France global forecasting model, ARPEGE, coupled to the LODYC oceanic model, OPA, by the CERFACS coupling package OASIS. The oceanic component is dynamically active over the tropical Pacific, whi le climatological time-dependent sea surface temperatures (SSTs) are p rescribed outside of the Pacific domain. The coupled model shows littl e drift and exhibits a very regular seasonal cycle, The climatological mean state and seasonal cycle are well simulated by the coupled model . In particular, the oceanic surface current pattern is accurately dep icted and the location and intensity of the Equatorial Undercurrent (E UC) are in good agreement with available data. The seasonal cycle of e quatorial SSTs captures quite realistically the annual harmonic. Some deficiencies remain including a weak zonal equatorial SST gradient, un derestimated wind stress over the Pacific equatorial band and an addit ional inter-tropical convergence zone (ITCZ) south of the equator in n orthern winter and spring. Weak interannual variability is present in the equatorial SST signal with a maximum amplitude of 0.5 degrees C. .