Norihisa Usui (Meteorological Research Institute, Japan); Tsuyoshi Wakamatsu (Japan Agency for Marine-Earth Science and Technology, Japan); Yusuke Tanaka (Japan Agency for Marine-Earth Science and Technology, Japan); Nariaki Hirose (Meteorological Research Institute, Japan); Takahiro Toyoda (Meteorological Research Institute, Japan); Shiro Nishikawa (Japan Agency for Marine-Earth Science and Technology, Japan); Yosuke Fujii (Meteorological Research Institute, Japan); Yasushi Takatsuki (Meteorological Research Institute, Japan); Hiromichi Igarashi (Japan Agency for Marine-Earth Science and Technology, Japan); Haruka Nishikawa (Japan Agency for Marine-Earth Science and Technology, Japan); Yoichi Ishikawa (Japan Agency for Marine-Earth Science and Technology, Japan); Masafumi Kamachi (Japan Agency for Marine-Earth Science and Technology, Japan)

Four-dimensional variational Ocean ReAnalysis for the western North Pacific over 30 years, FORA-WNP30, is an ocean reanalysis produced by Meteorological Research Institute, Japan Meteorological Agency (JMA/MRI) and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). The reanalysis is produced using a state-of-the-art 4-dimensional variational ocean data assimilation system, MOVE-4DVAR, developed in JMA/MRI (Usui et al., 2015). The ocean general circulation model used in MOVE-4DVAR is based on MRI.COM, the ocean model framework developed in JMA/ MRI (Tsujino et al., 2010). All the reanalysis calculation was carried out on the Earth Simulator with the support of JAMSTEC. It is the first-ever dataset covering the western North Pacific over three decades at eddy-resolving (about 10 km) resolution.
In-situ temperature and salinity profiles above 1500m-depth, gridded sea surface temperature (SST) and satellite altimeter-derived sea surface height (SSH) are assimilated in FORA-WNP30. The temperature and salinity profiles are collected from the World Ocean Database 2013 (WOD13) and the Global Temperature Salinity Profile Program (GTSPP). The gridded SST is Merged satellite and in situ Global Daily Sea Surface Temperature (MGDSST) compiled in JMA (Kurihara et al., 2006). The altimeter-derived SSH are AVISO along-track multimission products for TOPEX/Poseidon, Jason-1/2, ERS-1/2, Envisat, GFO and Cryosat-2. The SSH data is available since 1993, and the number of assimilated observations is closely linked to the number of satellite data.
FORA-WNP30 successfully reproduces the major ocean current such as the Kuroshio and Oyashio, and the associated meso-scale phenomena such as eddies, fronts, and meanders. In particular, it anomalous events such as the Kuroshio large meander and anomalous intrusion of the Oyashio even in 1980s, when there is not any satellite altimeter data. FORA-WNP30 is a valuable dataset for a variety of oceanographic research topics and potentially for related fields such as climate study, meteorology, and fisheries.
FORA-WNP30 is available as a basic ocean reanalysis dataset for wide- spread fields of climate/ocean research activities. Please refer ‘http://synthesis.jamstec.go.jp/FORA/e/’ for use of FORA-WNP30.