Abstract
Satellite altimeter data from both ERS-1 and TOPEX/POSEIDON have been assimilated into a 1/8° eddy-resolving model of the Pacific Ocean north of 20°S. We present strong evidence of significant oceanographic impact from this assimilation by direct comparison with two independent sets of observations, tide gauge sea level data and frontal locations from satellite infrared (IR) imagery. The assimilation of altimeter data provides marked and highly significant improvement in the accuracy of the model output in representing observed oceanic variations over most of the North Pacific basin. Additionally, it gives improved model accuracy in locating mesoscale eddies and meandering frontal structure in non-deterministic oceanographic regions like the Kuroshio-Kuroshio Extension. In regions where the ocean has a strong deterministic response to wind forcing, such as the equatorial region and along the American Pacific coast, the model has a high correlation with observed sea level variations before assimilation and the improvements are smaller. They are also small along the coast of Japan due to the importance of flow instabilities in this region and their relatively short time and space scales.
