Hindcasts of equatorial sea surface dynamic height in the Atlantic in 1982–1984

Abstract

Two different wind data sets of the years 1982–1984 are used to force a linear multimode model of the tropical Atlantic ocean. We describe the variations of the equtorial slope in both cases and investigate the differences between the two runs. The main discrepancy occurs in 1983 for the amplitude of the seasonal signal all along the equator. Model results are also compared with observations (hydrocasts and inverted echo sounders) taken during the Programme Français Océan et Climat dans l'Atlantique Equatorial/Seasonal Response of the Equatorial Atlantic (FOCAL/SEQUAL) field experiment (July 1982 through October 1984). The contrast between 1983 and 1984 is well captured by the two runs, especially the abnormal flat topography of the sea surface along the equator in the first 3 months of 1984 due to an unusual basin wide relaxation of the equatorial wind stress. The major discrepancy between model results and observations is found during the up welling periods east of 10°W, but at that time dynamic height measurements are too sparse to give a good description of these events.