The JRA-25 Reanalysis
Kazutoshi Onogi
Climate Prediction Division, Japan Meteorological Agency, Japankonogi @ [naps,met] .kishou.go.jp
1. Introduction
The Japan Meteorological Agency (JMA) and the Central Research Institute of Electric Power
Industry (CRIEPI) completed a cooperative research project named "Japanese 25-year Reanalysis(JRA-25)" in March 2006. JRA-25 is a long-term global atmospheric reanalysis produced using
JMA's data assimilation and forecast system and supercomputing resources provided by CRIEPI.
JRA-25 covers 26 years from 1979 to 2004. The latest version available in 2004 of JMA'snumerical data assimilation system and specially collected observational data were used to generate
a consistent and high quality reanalysis dataset designed for climatological research, operational
climate monitoring and seasonal forecasting. Since completion of the project, the JMA Climate
Data Assimilation System (JCDAS) has been successively operated by JMA with the same dataassimilation system as JRA-25, to generate quasi-real-time products. Onogi et al. (2007) provide
more details.
2. Observational data and NWP system used in JRA-25
Observational data used in JRA-25 were collected from the JMA archives and those supplied bymany organizations overseas such as the European Centre for Medium-Range Weather Forecasts(ECMWF), the National Center for Environmental Prediction (NCEP), the National Center for
Atmospheric Research (NCAR) and the National Climate Data Center (NCDC). Sets ofobservational data were also supplied by universities in Japan. In addition to conventional
observations, atmospheric motion vector (AMV) wind retrieved from geostationary satellites,
brightness temperature from TOVS and ATOVS, precipitable water retrieved from SSM/I radianceare assimilated with 3-dimensional variational method (3D-Var). JMA produced daily sea surface
temperature (SST) and sea ice named COBE, and 3-dimensional ozone profiles for JRA-25. A
new QC method for TOVS data was developed and applied in advance.
The global model used in JRA-25 has a spectral resolution of T106 (equivalent to a horizontal
grid spacing of around 120km) and 40 vertical layers with the top at 0.4hPa.
3. Performance of JRA-25
JRA-25 has many advantages. Firstly, predicted 6-hour global total precipitation distribution
and amount are well reproduced both in space and time. The performance of the long time seriesof the global precipitation is the best among the other reanalyses with few unrealistic variations
from degraded satellite data contaminated by volcanic eruptions (Figure 1). Secondly, JRA-25 is
the first reanalysis which assimilated wind profiles around tropical cyclones reconstructed from
historical best track information; tropical cyclones were analyzed properly in all the global regions(Figure 2). Additionally, low-level cloud along the subtropical western coast of continents is wellsimulated and snow depth analysis is also of a good quality.

Figure 1 Global mean precipitation (mm/day)Time series of reanalyzed global mean precipitation and independent
precipitation datasets are shown. (Onogi et al. 2007)

Figure 2 TC representation rates (%) for JRA-25 (black) and ERA-40 (gray)
Only TCs located near the best track positions that have typical TC
structures are selected. (Onogi et al. 2007)

4. Application using JRA-25
JRA-25 was transitioned to JMA Climate Data Assimilation System (JCDAS) using the samedata assimilation system of JRA-25. JRA-25 and JCDAS are used in various operational climate
services of JMA and are available via the internet for research use. A new climatic normal values
and related indices are produced using the consistent JRA data and the previous normal wasreplaced. It improves the quality of climate monitoring and is beneficial for seasonal forecast,ocean monitoring and development of seasonal numerical model. JRA data is used as a basic
dataset in a newly established Japanese Advisory Panel on Extreme Climatic Events which consistsof 10 prominent experts from universities and research institute. The JMA operational SST
analysis and forecast were improved by a development using the JRA data. Application using
JRA-25 and JCDAS data are summarized in Figure 3.

Figure 3

Application of JRA-25 for operation and research5. JRA-25 Atlas"JRA-25 Atlas" which visualized many kinds of meteorological climate fields of JRA-25 has
been published. The Atlas contains maps, cross sections and plots of time series. Maps and crosssections include annual and seasonal averages. Figures for interannual variability show standard
deviations for the 26 years that are calculated and drawn for annual averages. Seasonal averages
are shown for Dec. - Feb., Mar. - May, Jun. - Aug. and Sep. - Nov. except for figures relating totropical cyclones. Most of the figures are drawn directly from monthly averages or monthly
normal values available from the JRA-25 official web page, using T106 Gaussian grid data. Somefigures are drawn from 2.5-degree latitudinal-longitudinal grid data. A few sample maps of theAtlas are shown in Figure 4.
The Atlas is going to be available on the JMA official web site including maps of monthly
averages as well as annual and seasonal averages.

Figure 4 (1) JRA-25 Atlas : Distribution of tropical cyclones(annual mean; existing day/month)Figure 4 (2) JRA-25 Atlas : Annual mean precipitation(annual mean; mm/day)6. JRA-50 : The next Japanese Reanalysis
JMA will conduct the next new reanalysis named JRA-50, which covers more than 50 years from1958 to present. JRA-25 provides consistent climate data and contributes largely for research andoperational activities, but the 26 years of JRA-25 are not sufficient period for comprehensive
analysis of climate change and global warming. The purposes of JRA-50 is to 1) produce longer
climate database with higher quality than JRA-25; 2) resolve deficiencies of JRA-25; 3) analyze
past global warming with higher quality. Since the performance of the JMA operational numericalprediction has been improved significantly in recent years, we can take the improvements into
account for JRA-50 data assimilation system. JRA-50 production will be started from early 2009
after preparation and experiment stage in 2008. The production requires about 5 years and will beterminated at the end of 2013.
Differences between JRA-25 and JRA-50 are summarized in Table 1.
Table 1 Comparison between JRA-25 and JRA-50
JRA-25
1979-2004 (26 years)
T106L40 top at 0.4hPa
3D-var (Inner T106)
Eular scheme
Normal Gaussian Grid system
Physics
Previous scheme except cloudscheme
Forecast Score
13m (NH), 19m (SH)
(Z500
RMSE (as of Mar. 2004)
FT=24)
Sounder data
TOVS 1d, ATOVS 1cYears
Model Resolution
Data Assimilation
Numerics

reprocessed AMV

Meteosat-2 and GMS-3,4,5

SSM/I
CO2
Observation history
and QC

Precipitable water
constant (space & time)
specified QC for TOVSAndraeetal.(2004)
Onogi(2000) for RAOB
3D-daily profile
JCDAS (operational)

Ozone
CDAS mode

JRA-501958-2012 (55 years)
TL319L60 top at 0.1hPa
4D-var (Inner T106)
Semi-Lagrangean scheme
Reduced Gaussian Grid system
Improved radiation (bias reduced)
Improved land surface scheme
9m (NH), 12m (SH)(as of Dec. 2007, to be improvedmore)
TOVS 1c, ATOVS 1c, VTPR,AMSR-E etc.
Meteosat-2 to 7 and
GMS-3,4,5(revised) GOES?
Radiance
Historical
Feedbacks from ERA-Interimwith Using JRA-25 archives
3D-daily profile (revised)
To be transitioned to New JCDAS

Reference
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.
http://www.jstage.jst.go.jp/article/jmsj/85/3/369/_pdf
JRA official page : http://jra.kishou.go.jp/index_en.html