Horizontal and vertical structure of the representer functions for sea surface measurements in a coastal circulation model

The representer functions used to propagate the information from observations onto model variables in a sequential data assimilation scheme are calculated with a statistical method. The Princeton Ocean Model is used in a simple configuration simulating the North Current flowing along the French coasts in the northwestern Mediterranean Sea. The influence of sea level measurements on the models' three-dimensional temperature and velocity fields is investigated. Inhomogeneities and directions of anisotropy are evidenced. A comparison with simplified reduced order assimilation methods suggests that such schemes will not allow for consistent assimilation of nearshore altimetric data.