Assimilation of SLA along track observations in the Mediterranean with an oceanographic model forced by atmospheric pressure

A large number of SLA observations at a high along track horizontal resolution are an important ingredient of the data assimilation in the Mediterranean Forecasting System (MFS). Recently new higher frequency SLA products have become available, and the atmospheric pressure forcing has been implemented in the numerical model used in the MFS data assimilation system. In a set of numerical experiments we show that in order to obtain the most accurate analyses the ocean model should include the atmospheric pressure forcing and the observations should contain the atmospheric pressure signal. When the model is not forced by the atmospheric pressure the high frequency filtering of SLA observations, however, improves the quality of the analyses. It is further shown that MFS analyses, produced by an assimilation system given by the numerical model and the high frequency SLA observations, have a correct power spectrum at high wave numbers and they filter efficiently the SLA assimilated observations which, on the other hand, are contaminated by high wavenumber noise.