Data Assimilation Applied to the Temperature and Circulation in the Tropical Atlantic, 1983–84

Abstract A hydrographic dataset based on data from the SEQUAL/FOCAL experiment is used to determine the errors of a numerical simulation of the complete temperature and velocity fields of the tropical Atlantic during the two-year period 1983–84. To improve the accuracy of the analysis we develop an application of four-dimensional data assimilation. In this analysis the thermal fields of the model are updated once a month using sea surface temperature measurements and observed temperature profiles. Much of the paper describes comparisons between differing analyses using data assimilation and the numerical simulation, and verification of these with temperature and velocity data from moored instruments. Assimilation of the temperature observations improves the accuracy of the temperature analysis. The amplitude of seasonal changes in the meridional thermal gradient is doubled at 38°W, bringing the analysis closer to the observed thermal gradient. At 28°W the improved is less dramatic. The zonal thermal gradi...