Recent advances in our knowledge of the earth geoid have made it possible to exploit absolute sea surface height measurements in realistic numerical modelling studies of the ocean. This letter provides evidence of the benefit of the GRACE referenced mean dynamic topography (MDT) for the simulation of the tropical Pacific ocean through the joint assimilation of altimetric data and of vertical temperature profiles from the TAO/TRITON array. Results are considered in relation to those obtained using a classical model MDT, based on the model itself, and are validated against independent XBT data. The use of the GRACE MDT leads to significantly improved results with respect to these independent data. If the compatibility between the altimetric sea surface height and the TAO/TRITON temperature improves the model simulation, some limitations exist, especially in the Warm Pool where a part of the sea surface height signature is associated to a salinity signal.