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Dataset

Four-dimensional Ocean ReAnalysis for the seas around Japan (FORA-JPN60) is produced by using MOVE-JPN (Hirose et al., 2019) which is an operational ocean system in Japan Meteorological Agency (JMA). MOVE-JPN is based on Meteorological Research Institute Community Ocean Model (MRI.COM, Sakamoto et al., 2023) as ocean-sea ice coupling model and MRI Multivariate Ocean Variational Estimation with 4D-Var (MOVE-4DVAR, Usui et al., 2015), both of which are developed by the MRI/JMA. Table 1 summarizes the main configuration of the Japanese Coastal Model (JPN) and the North Pacific Model (NP), which are being released as FORA-JPN60. Table 2 summarizes the observational data collected during the FORA-JPN60 experiment. Table 3 lists the output variables to be released. The FORA-JPN60 reanalysis experiment was carried out on the Earth Simulator at JAMSTEC and Fujitsu Server PRIMERGY CX2550 M5 at JMA/MRI. Please see Usui et al., (2026) in detail.

Table 1．Main configuration of the FORA-JPN60

	Japanese Coastal model (JPN)	North Pacific (NP)
Ocean model	MRI.COMv5
Model domain	117°E-160°E, 20°N-52°N	99°E-75°W, 15°S-63°N
Horizontal resolution	1/33° x 1/50°	1/11° x 1/10°
Vertical resolution	2 – 700 (m)
Grid	1423 x 1604 x 60	2049 x 784 x 60
Atmospheric forcing	JRA-3Q
River forcing	Japanese rivers：JMA runoff index Except Japanese rivers：JRA55 + CaMaFlood
Tidal forcing	Major 8 components
Sea level pressure	Applied
Nesting	2-way online nesting
Data assimilation (ocean)	4D-Var (10-day cycle with 3-day overlap） IAU downscaling (5 days)
Observation (SST)	gridded sea surface temperature product MGDSST
Observation (SSH)	along-track sea level anomaly with non-steric correction
Observation (in-situ temperature/salinity)	EN4, WOD18, GTSPP, JODC, MODS2005, FRESCO, KODC, Fishery experiment institutes, Local prefecture (Table 2)
Data assimilation (sea ice)	Nudging
Observation (sea ice concentration)	JMA’s sea ice analysis for the Okhotsk Sea	SSMI, SSMIS
Reanalysis period	1960-2020

Table 2. In-situ observation data

Area	Dataset	Using period
Global	EN4	1960-2020
	WOD18	1960-2020
	GTSPP	1985-2020
North Pacific	JODC	1960-2020
	MIRC Ocean Dataset 2005	1960-2020
Japan	FRESCO	2003-2015
	KODC	1964-2020(bimonthly)
	Observation report in southwest of Okhotsk by the Japan Coast Guard	2003-2020 (only February)
	Observing System for Aquatic Quality at Automated Stations in Osaka Bay	2010-2020
	Seto Inland Sea Comprehensive water quality survey by Ministry of the Land, Infrastructure, Transport, and Tourism	1982-2020 (4 times per year)
	Broad Comprehensive Water Quality Survey by Ministry of the Environment	1978-2020 (4 times per year)
	Hokkaido Research Organization	2008-2018
	Aomori Prefecture	2008-2020

Variables

Data format : NetCDF-4 (except for 1-dimensional data, which are provided in Fortran single-precision binary)

Table 3.1 Daily-mean and Monthly-mean variables

	JPN	NP
3-dimension	Zonal and meridional velocity, potential temperature, salinity, vertical tracer diffusivity	Same with JPN
2-dimension	Sea surface temperature, sea surface height, IB corrected sea surface height, reproduce tidal height for major 8 tidal component Zonal vertical integrated velocity, meridional vertical integrated velocity, sea bottom pressure Sea surface heat fluxes (shortwave longwave, sensible heat, latent heat) Sea ice concentration, sea ice thickness, sea ice velocity (zonal and meridional)	Same with JPN
1-dimension	Volume transport through the Japan Sea (eastern channel of Tsushima Strait, western channel of Tsushima Strait, Tsugaru Strait, Soya Strait, Mamiya Strait)	None

Table 3.2 Snapshot at 30-minute intervals

	JPN	NP
2-dimension	Sea surface height, IB corrected sea surface height, zonal and meridional vertical integrated velocities, zonal and meridional sea surface velocities, sea surface temperature	Sea surface height, IB corrected sea surface height, zonal and meridional vertical integrated velocities

References
Usui, N., N. Hirose, K. Sakamoto, H. Asai, S. Nishikawa, H. Igarashi, Y. Kawakami, K. Aoki, H. Nakano, Y. Ishikawa, 2026: Four-dimensional variational ocean reanalysis for the seas around Japan over 60 years (FORA-JPN60): Part I – system configuration and basic performance. J. Oceanogr., doi;10.1007/s10872-026-00795-x

Hirose N, Usui N, Sakamoto K, Tsujino H, Nakano GYH, Urakawa S, Toyoda T, Fujii Y, Kohno N (2019) Development of a new operational system for monitoring and forecasting coastal and open-ocean states around japan. Ocean Dyn 69:1333–1357,https://doi.org/10.1007/s10236-019-01306-x

Sakamoto K, Nakano H, Urakawa S, Toyoda T, Kawakami Y, Tsujino H, Yamanaka G (2023) Reference manual for the meteorological research institute community ocean model version 5 (mri.comv5). Tech. Rep. 87, Meteorol. Res. Inst., Tsukuba, Japan,DOI :10.11483/mritechrepo.87

Usui N, Fujii Y, Sakamoto K, Kamachi M (2015) Development of a four-dimensional variational assimilation system for coastal data assimilation around japan. Mon Wea Rev 143:3874–3892,https://doi.org/10.1175/MWR-D-14-00326.1