Four dimensional variational reanalysis of Western North Pacific Ocean - system configuration, performance and validation

Eddy resolved (1/10 degree), long term (1982-current) ocean reanalysis data, FORA-WNP30, over Western North Pacific Ocean (117E-160W, 15N-65N) are newly derived using cycled 4DVar data assimilation system with 10 day assimilation period in its each cycle. The reanalysis project was led by joint group of Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and Meteorological Research Institute (MRI), Japan. Preliminary validation studies show that temporal variation of Kuroshio meandering path off the southern coast of Japan and extreme Oyashio southern intrusion events off the east coast of Japan are well reproduced throughout the entire analysis period. These findings support that this new reanalysis data is capable of reproducing variations of meso-scale ocean structures nearby Japan coasts during the pre-satellite altimetry era. Observation sensitivity experiment conducted in parallel to the main reanalysis calculation also reveals geographical region where the meso-scale features can be reproducible without altimeter data in our reanalysis system. In this presentation, detail information on the reanalysis system set-up, performance of the reanalysis system and the validation of the 4DVar assimilation system will also be reported.