Reanalysis

The need for quantitative assessment of past and current climate conditions gives rise to the requirement for a high-quality dataset with homogeneity in space and time to support climate research and related services such as seasonal forecasts, extreme weather analysis and climate monitoring.

The quality of analysis produced by the operational numerical weather prediction (NWP) system has improved remarkably in recent years due to advances made with the system. Consequently, the difference in the quality of analysis produced with previous operational NWP systems and the current system creates a lack of long-term data homogeneity.

To produce a high-quality homogeneous dataset, a constant state-of-the-art data assimilation system is used in reanalysis. In addition, as many observations as possible are collected, including those used in past operational systems and delayed observations as well as digitized observations. High-quality reprocessed satellite data are also assimilated where available. These approaches enable the production of a higher-quality and more homogeneous dataset for a variety of meteorological variables covering the last several decades.

Global reanalysis has been conducted at a number of major NWP centers (for more information, see https://reanalyses.org/). In this context, the Japan Meteorological Agency (JMA) and the Central Research Institute of Electric Power Industry (CRIEPI) in Japan jointly conducted the Japanese 25-year Reanalysis (JRA-25, covering the period from 1979 to 2004 and completed in 2006), and JMA conducted the Japanese 55-year Reanalysis (JRA-55, covering the period from 1958 onward and completed in 2013).

Japanese Reanalysis for Three Quarters of a Century (JRA-3Q)

JMA is currently conducting the Japanese Reanalysis for Three Quarters of a Century (JRA-3Q), which covers the period from September 1947 onward to extend the current period of data coverage and improve the quality of long-term reanalysis. The project involves a sophisticated data assimilation system (based on the operational set-up as of December 2018) incorporating development results from the operational NWP system and sea surface temperature analysis achieved since JRA-55 (based on the operational set-up as of December 2009). New datasets of past observations are also assimilated, including rescued historical observations and reprocessed satellite data supplied by meteorological and satellite centers worldwide. Many of the deficiencies of JRA-55 are alleviated in JRA-3Q, providing a high-quality homogeneous reanalysis dataset that covers the previous 75 years.

Sub-product JRA-3Q-COBE

In JRA-3Q, the sea surface temperature (SST) specified as the lower boundary condition is the Centennial In Situ Observation-based Estimates of the Variability of SSTs and Marine Meteorological Variables Version 2 (COBE-SST2) with a resolution of 1° based on in situ observations until May 1985 and the Merged Satellite and In-Situ Data Global Daily Sea Surface Temperature (MGDSST) with a resolution of 0.25° based on satellite observations since June 1985. To enable evaluation of changes in product characteristics following the switch from COBE-SST2 to MGDSST, a sub-product using COBE-SST2 (JRA-3Q-COBE) is also provided for the period from June 1985 to December 1990.

JRA-3Q comprehensive report

Reference JRA-3Q data in scientific or technical papers should be cited to the JRA-3Q comprehensive report below.

• Kosaka, Y., S. Kobayashi, Y. Harada, C. Kobayashi, H. Naoe, K. Yoshimoto, M. Harada, N. Goto, J. Chiba, K. Miyaoka, R. Sekiguchi, M. Deushi, H. Kamahori, T. Nakaegawa; T. Y.Tanaka, T. Tokuhiro, Y. Sato, Y. Matsushita, and K. Onogi, 2024: The JRA-3Q reanalysis. J. Meteor. Soc. Japan, 102, 49-109, https://doi.org/10.2151/jmsj.2024-004.

Reference

• Naoe, H., C. Kobayashi, S. Kobayashi, Y. Kosaka, and K. Shibata, 2025: Representation of quasi-biennial oscillation in JRA-3Q. J. Meteor. Soc. Japan, 103, https://doi.org/10.2151/jmsj.2025-012.

Links

• 6th WCRP International Conference on Reanalysis
• Joint WCRP-WWRP Symposium on Data Assimilation and Reanalysis and 2021 ECMWF Annual Seminar on Observations

How to obtain data

The data are widely provided to the public through the Japan Meteorological Business Support Center (JMBSC).
If you would like to use JRA-3Q data, please obtain the data from JMBSC.

For more information, please visit the JMBSC website.

JRA-3Q data are also provided by collaborative organizations for non-commercial purposes.
Please note the following in regard to downloading data from these organizations:

• Collaborative organizations are separate entities from JMA and are solely responsible for their own web portals and data access procedures.
• User registration and agreement to terms and conditions of data service usage are required individually for each organization.

Collaborative organizations

1. DIAS: Data Integration & Analysis System

   Data access to JRA-3Q
   • Metadata page: https://search.diasjp.net/en/dataset/JRA3Q, DOI: 10.20783/DIAS.645
   Data access to JRA-3Q-COBE (JRA-3Q with COBE-SST2)
   • Metadata page: https://search.diasjp.net/en/dataset/JRA3Q_COBE, DOI: 10.20783/DIAS.661

   When publishing results using data provided from DIAS, please cite the dataset in addition to the above-mentioned JRA-3Q comprehensive report (see each metadata page as to how to cite the dataset).

2. NCAR: National Center for Atmospheric Research

   Data access to JRA-3Q
   • Metadata page: https://rda.ucar.edu/datasets/d640000, DOI: 10.5065/AVTZ-1H78
   Data access to Near Real-Time JRA-3Q
   • Metadata page: https://rda.ucar.edu/datasets/d640001, DOI: 10.5065/E3QQ-0F24
   Data access to JRA-3Q Monthly Statistics
   • Metadata page: https://rda.ucar.edu/datasets/d640002, DOI: 10.5065/PH0D-MH18
   Data access to Near real-time monthly mean JRA-3Q
   • Metadata page: https://rda.ucar.edu/datasets/d640003, DOI: 10.5065/CW01-2282
   Data access to JRA-3Q Diurnal Statistics
   • Metadata page: https://rda.ucar.edu/datasets/d640004, DOI: 10.5065/PK9Z-C990
   Data access to Near real-time monthly diurnal JRA-3Q
   • Metadata page: https://rda.ucar.edu/datasets/d640005, DOI: 10.5065/4Q9N-SG67
   Data access to JRA-3Q-COBE
   • Metadata page: https://rda.ucar.edu/datasets/d640006, DOI: 10.5065/RM7V-3X70

   When publishing results using data provided from NCAR, please cite the dataset in addition to the above-mentioned JRA-3Q comprehensive report (see each metadata page as to how to cite the dataset).

Data source acknowledgement

JRA-3Q data should be acknowledged in scientific and technical reports.

• Example

  This report references JRA-3Q reanalysis data from the Japan Meteorological Agency.

  This report references JRA-3Q-COBE reanalysis data from the Japan Meteorological Agency.

Remaking metafiles for JRA-3Q data visualization

Data descriptor files (*.ctl) and index files (*.idx) can be used in addition to JRA-3Q data for visualization of JRA-3Q data with multi-purpose Grid Analysis and Display System (GrADS) software.

When information in data descriptor files (e.g., time periods and other variables) is changed, the corresponding index files need to be remade.

• To remake an index file

  $ gribmap -b -i [data descriptor file]