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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

11 October 2018
Replacement of the missing data in the JRA-55 product
JRA-55 Product Users' Handbooks are updated.
2 October 2018
Partially missing data in the JRA-55 product
8 December 2017
Due to restrictions of the storage resources, the directories for the period from January 1971 to September 1980 (for all categories) will be moved.
  • Following this move, a switch of the symbolic links under the JRA-55/Hist/Daily directory will take place on 11 December 2017, 04-06 UTC.
  • Please be informed that the symbolic links to the directories for the aforementioned period will be temporarily disconnected during this switch.
25 October 2017
Provision of the model grid isentropic analysis fields (anl_isentrop) for the past period (1958-2016) from the JMA Data Dissemination System (JDDS) will be terminated as of the end of October 2017.
  • Due to restrictions of the storage resources, provision of the above data from JDDS will be terminated.
  • The above data at DIAS and NCAR will remain available, and can be downloaded from these collaborative organizations as ever.
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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

JMA provides JRA-55 dataset via the JMA Data Dissemination System (JDDS).


Applications are required to download and use JRA-55 data via the JDDS.
Please register to use the data.

  • The user ID and the associated password provided are valid only for the JDDS.
  • Applications should not be made through this site to obtain JRA-55 data from a collaborative organization. Individual user registration is required for each organization.
    See a Collaborative organizations providing the JRA-55 data.

Change password/email address

Passwords and email addresses registered with the JDDS can be changed at the URL below.
The period of password validity is four months.
Users will receive an email from JDDS_admin every day from two weeks before the expiration date.

To change a password or email address

  1. Access the following link and log on with the ID and current password.
  2. Input the current password and the new password/email address.

Downloading JRA-55 data

JRA-55 data can be downloaded using FTP. The procedure is outlined below.


$ ftp ds.data.jma.go.jp # log-on to the JMA Data Dissemination System (JDDS)
????????                # user ID
********                # password
binary                  # changes transfer mode to binary
cd JRA-55/Hist/Monthly/anl_surf125
get anl_surf125.195801
get anl_surf125.195802
  • When connection is made through a firewall, the hostname and user ID specification may be different from the above example. For details, contact your network administrator.
  • The JDDS has recently experienced heavy traffic due to an increased number of accesses. Making multiple connections or remaining connected for extended periods can place an excessive load on the server and interfere with normal operation.
    Please refrain from making multiple connections and remaining connected for extended periods when downloading data.
    Users are asked to kindly limit connection time to 12 hours a day in total.
    Your cooperation in reducing the server load is appreciated.


    logon >> download (1 hour) >> logoff >> break (1 hour) >> logon >> …

Collaborative organizations providing JRA-55 data

JRA-55 data are provided by collaborative organizations as well as by JMA.
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

  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):

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).

11 October 2018
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.

Climate Prediction Division,
Global Environment and Marine Department,
Japan Meteorological Agency

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