Assimilation of altimeter wave height data into a spectral wave model using statistical interpolation

A scheme for the assimilation of altimeter wave height data into a second generation wave prediction model is developed. The scheme modifies the model wave spectrum so as to be consistent with the satellite observed values of significant wave height. This modification is achieved, however, so that the adjusted wave field is consistent with the model physics and the forcing wind field. In this manner the modifications to the wave field persist in the model, thus yielding long term improvements in model performance. In addition, a statistical interpolation scheme is used to ensure that maximum use is made of the point observations made by the satellite. In this manner, not only points directly beneath the satellite track are updated. Points adjacent to the track are also modified, the extent of this modification depending on the spatial correlation of the wave field. The scheme is applied to a computationally efficient second generation wave model. The improvement in performance is significant, demonstrating that assimilation may be a very efficient alternative to proceeding to more sophisticated and expensive third generation models. This is particularly true where the forcing wind field may be of poor quality. The results also demonstrate that with the addition of assimilation, relatively small computational grids can be utilized. Swell generated external to the grid will be included through the assimilation cycle.