Assimilation of Temperature Profiles in a General Circulation Model of the Tropical Atlantic

Abstract

Thirty-six hundred temperature profiles collected during 1984 were assimilated into a multilayer primitive equation model of the tropical Atlantic Ocean. The method consists in a monthly correction of the simulated temperature field. Each month, an observed field is computed from the temperature profiles with a successive correction analysis starting from the simulated field. The difference between the observed field and simulation is computed, the model is restarted from the previous month, progressively introducing the difference as a Newton forcing in the heat equation. The sensitivity to the initial mate is greatly reduced near the equator after six months, but persists for a longer time at higher latitudes. The assimilated temperature structure is closer to the observations than was the unassimilated simulation. The thermocline has strengthened, and low-frequency variability the equator is close to the observe one, resulting in a more realistic zonal slope of the thermocline. The current structure, although it still differs noticeably from the observations, is more realistic, with stronger near-surface countercurrents and a faster equatorial undercurrent.