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 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 leaflet

• Printer-friendly version (trifold leaflet)
• On-screen version

JRA-55 comperehensive reports

• Kobayashi, S., Y. Ota, Y. Harada, A. Ebita, M. Moriya, H. Onoda, K. Onogi, H. Kamahori, C. Kobayashi, H. Endo, K. Miyaoka, and K. Takahashi , 2015: The JRA-55 Reanalysis: General specifications and basic characteristics. J. Meteor. Soc. Japan, 93, 5-48, doi:10.2151/jmsj.2015-001.
  
• Harada, Y., H. Kamahori, C. Kobayashi, H. Endo, S. Kobayashi, Y. Ota, H. Onoda, K. Onogi, K. Miyaoka, and K. Takahashi, 2016: The JRA-55 Reanalysis: Representation of atmospheric circulation and climate variability, J. Meteor. Soc. Japan, 94, 269-302, doi:10.2151/jmsj.2016-015.
  

JRA references

• Kobayashi, C., and T. Iwasaki, 2016: Brewer-Dobson circulation diagnosed from JRA-55. J. Geophys. Res. Atmos., 121, doi:10.1002/2015JD023476.
  
• Ebita, A., S. Kobayashi, Y. Ota, M. Moriya, R. Kumabe, K. Onogi, Y. Harada, S. Yasui, K. Miyaoka, K. Takahashi, H. Kamahori, C. Kobayashi, H. Endo, M. Soma, Y. Oikawa, and T. Ishimizu, 2011: The Japanese 55-year Reanalysis "JRA-55": an interim report, SOLA, 7, 149-152, doi:10.2151/sola.2011-038.
  
  (This article is an interim report of JRA-55 as of 2011. Please refer the above articles Kobayashi et al. 2015 and Harada et al. 2016 for the JRA-55 comprehensive reports.)
• Onogi, K., J. Tsutsui, H. Koide, M. Sakamoto, S. Kobayashi, H. Hatsushika, T. Matsumoto, N. Yamazaki, H. Kamahori, K. Takahashi, S. Kadokura, K. Wada, K. Kato, R. Oyama, T. Ose, N. Mannoji and R. Taira, 2007: The JRA-25 Reanalysis. J. Meteor. Soc. Japan, 85, 369-432, doi:10.2151/jmsj.85.369.

Links

• JMA Top Page
• CRIEPI Website
• 5th International Conference on Reanalysis
• 4th WCRP International Conference on Reanalyses
• 3rd WCRP International Conference on Reanalysis

Collaborative organizations providing JRA-55 data

Important Notice: Update of the near real-time JRA-55 data was 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.

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):

   • Daily 3-Hourly and 6-Hourly Data http://rda.ucar.edu/datasets/ds628.0/
   • Monthly Means and Variances http://rda.ucar.edu/datasets/ds628.1/
   • Near Real-Time Data http://rda.ucar.edu/datasets/ds628.8/
   • Near Real-Time Data -- Monthly Means and Variances http://rda.ucar.edu/datasets/ds628.9/
   
   Data access to JRA-55C (an atmospheric reanalysis assimilating conventional observations only):
   • Daily 3-Hourly and 6-Hourly Data http://rda.ucar.edu/datasets/ds628.2/
   • Monthly Means and Variances http://rda.ucar.edu/datasets/ds628.3/
   
   Data access to JRA-55AMIP (JRA-55 AMIP-type simulation):
   • Daily 3-Hourly and 6-Hourly Data http://rda.ucar.edu/datasets/ds628.4/
   • Monthly Means and Variances http://rda.ucar.edu/datasets/ds628.5/

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]