Combining altimetric/gravimetric and ocean model mean dynamic topography models in the GOCINA region

Initially, existing mean dynamic topography (MDT) models were collected and reviewed. The models were corrected for the differences in averaging period using the annual anomalies computed from satellite altimetry. Then a composite MDT was derived as the mean value in each grid node together with a standard deviation to represent its error. A new synthetic MDT was obtained from the new mean sea surface (MSS) KMS04 combined with a regional geoid updated using GRACE gravity and gravimetric data from a recent airborne survey. Compared with the composite MDT the synthetic MDT showed very similar results. Then combination methods were tested for the computation of MDT models from gravity data and MSS data. Both a rigorous and an iterative combination method have been tested in the GOCINA region. At this stage, the iterative combination method with its efficient handling of large data sets covering the whole region appears to give the best solution. Naturally, the errors associated with the MDT can be obtained using the rigorous method only