Japanese >>

JRA project

JRA-55 – the Japanese 55-year Reanalysis

The second Japanese reanalysis project conducted by the Japan Meteorological Agency (JMA), which cover the period from 1958 onward.

Latest News

23 January 2024
The abstract submission for the 6th WCRP International Conference on Reanalysis (in Tokyo from 28 October to 1 November 2024) is now open. Submission deadline is 24 March 2024, 23:59JST.
5 December 2023
Important Notice: Update of the near real-time JRA-55 data will be terminated at the end of January 2024.
  • JRA-55 data produced so far will remain available from collaborative organizations.
  • JRA-3Q data, including near real-time update, are now available from DIAS and NCAR as the succeeding product. More details are provided at the JRA-3Q website.
Archive >>



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 Data Assimilation (DA) 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 DA systems and the current system creates a lack of long-term data homogeneity.

To produce a high-quality homogeneous climate dataset, a constant state-of-the-art DA 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 higher-quality and more homogeneous climate data for a variety of meteorological variables covering the last several decades.

Global reanalysis has been conducted at a number of major Numerical Weather Prediction centers (for more information, see http://www.reanalyses.org/). In Japan, the Japan Meteorological Agency (JMA) and the Central Research Institute of Electric Power Industry (CRIEPI) jointly conducted the Japanese 25-year Reanalysis (JRA-25, covering the period from 1979 to 2004) and completed in 2006 (Onogi et al. 2007).

JRA-55 – the Japanese 55-year Reanalysis

JMA carried out the second reanalysis project (known as the Japanese 55-year Reanalysis, or JRA-55) using a more sophisticated DA system based on the operational system as of December 2009, and newly prepared dataset of past observations. The analysis period covers the 55 years from 1958, when regular radiosonde observation began on a global basis. Many of the deficiencies of JRA-25 are alleviated in JRA-55 because the DA system used for the project featured a variety of improvements introduced after JRA-25. As a result, the JRA-55 project produced a high-quality homogeneous climate dataset covering the last half century.

JRA-55 comperehensive reports

JRA references

Usage of JRA-55

Collaborative organizations providing JRA-55 data

JRA-55 data are provided by collaborative organizations.
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-55 (an atmospheric reanalysis) : http://search.diasjp.net/en/dataset/JRA55
    Data access to JRA-55C (an atmospheric reanalysis assimilating conventional observations only) : http://search.diasjp.net/en/dataset/JRA55_C
    Data access to JRA-55AMIP (JRA-55 AMIP-type simulation) : http://search.diasjp.net/en/dataset/JRA55_AMIP
    Data access to JRA-55CHS (an atmospheric reanalysis assimilating conventional observations only with high resolution SST) : http://search.diasjp.net/en/dataset/JRA55_CHS

  2. NCAR: National Center for Atmospheric Research (USA)

    Data access to JRA-55 (an atmospheric reanalysis):

    Data access to JRA-55C (an atmospheric reanalysis assimilating conventional observations only):
    Data access to JRA-55AMIP (JRA-55 AMIP-type simulation):

Remaking/updating metafiles for JRA-55 data visualization

Data descriptor files (*.ctl) and index files (*.idx) can be used in addition to JRA-55 data for visualization of JRA-55 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 or updated.

  • To remake an index file

    $ gribmap -b -i [data descriptor file]
  • To update an index file

    If the change involves only the time period, the relevant information can simply be added to the existing file.

    $ gribmap -b -u -i [data descriptor file]

JRA-55 Product Users' Handbook

These documents give an overview of JRA-55 data and changes from corresponding JRA-25 data (Onogi et al. 2007).

2 July 2021
1.25-degree latitude/longitude grid data
model grid data (TL319L60)

Adobe Reader® must be installed to enable viewing of Portable Document Format (PDF) files.

Quality Issues

Contact Us

Contact JMA at the email address below with any questions on JRA-55.

Numerical Prediction Division,
Information Infrastructure Department,
Japan Meteorological Agency

  • Questions on JRA data (JRA-55, JRA-25/JCDAS)
  • And other questions