Variational assimilation of altimeter data into a Non-linear ocean model: temporal strategies

In this paper, we explore the use of the adjoint method in the oceano-graphic context for assimilating satellite altimeter data. Experiments with simulated altimeter data are performed in a multi-layer quasigeostrophic ocean model. The interest is mainly with controlling the mesoscale eddy active ocean circulation observed in the mid-latitudes. Due to the surface nature of the observations, one key aspect in the success of assimilation is its ability to transfer the surface data information downwards to the deep flows. Test experiments are performed rst, in a coarse resolution regional basin within which several eddies are interacting on the f-plane and sec-ond, in a high resolution basin size domain on the -plane which mimics the Gulfstream-like behavior of mid-latitude jets and western boundary currents and the associated eddy system. As a matter of fact, it is found that the length of the assimilation cycle is crucial to the success of this assimilation. Short assimilation cycle