Impact of data from upcoming altimetric missions on the prediction of the three-dimensional circulation in the tropical Atlantic Ocean

The use of Sea Surface Height (SSH) satellite measurements in ocean models is a key element in the efficient control of the three-dimensional circulation through data assimilation and therefore in the quality of operational oceanography products. This paper attempts to evaluate the impact of future satellite data, particularly from the upcoming JASON2, SARAL and SWOT missions, introduced into a model through a sophisticated data assimilation procedure. For this purpose, Observing System Simulation Experiments (OSSEs) are performed in the tropical Atlantic Ocean. The NEMO model is used (at a 1/4° resolution) in a configuration covering the tropical Atlantic from 15°S to 17°N, and the assimilation scheme is a reduced-order Kalman (SEEK) filter. The study focuses principally on controlling of the circulation of the North Brazil Current and the propagation of Tropical Instability Waves (TIW). Among the orbits tested for altimetric satellites, the JASON2 orbit (10-day repeat period) is found to give the best single satellite sampling for data assimilation. The addition of a second or third satellite to JASON2 is particularly useful in the TIW region and is even required to properly control the Brazil rings. A SWOT satellite would provide benefits that are equivalent to the contribution of two or three satellites, depending on the case.

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