JRA-55

The Japanese 55-year Reanalysis

I’m Harerun

The number five ispronounced go in Japanese.
So the JRA-55 is called JRA go! go!

OUTLINEIn response to the success of JRA-25, JMA
conducted the second Japanese global reanalysis,
called JRA-55. The project involved comprehensive
global atmospheric reanalysis based on fourdimensional variational analysis (4D-Var) for the last
half of the 20th century (1958 onward). As a result,
the two major biases found in JRA-25 have beensignificantly alleviated and the temporalconsistency of temperature analysis is also better
than that of previous analysis products.
The high-quality and long-term JRA-55 data
produced are suitable for studies on climate change
and multi-decadal variability as well as for themonitoring of current climate systems.

DATA ASSIMILATION SYSTEM
The data assimilation system is based on JMA’s
operational model as of December 2009, andimproves on JRA-25 in many ways. Enhancements
include a revision of the radiation scheme and theintroduction of 4D-Var and variational bias
correction (VarBC) for satellite radiances. These
upgrades significantly reduce model biases,
enhance the dynamical consistency of analysis fields
and advance the handling of satellite radiances.
Resolution & levels

TL319 (~ 55 km), 60 levels up to 0.1 hPa

Advection scheme

Semi-LagrangianAssimilation

Japan Meteorological Agency

4D-Var, 6h time window, T106 inner model

Satellite radiancebias correction

VarBC (Dee and Uppala 2009)

Radiative transfer
model for satellite

RTTOV-9.3 (Saunders et al. 2008)

Long wave radiation
schemeLine absorptions; Pre-computed
Transmittance Tables and k-distribution(Chou et al. 2001)
Water vapor continuum (e-type and p-type);
Zhong and Haigh (1995) with MK_CKD V1.0
Radiatively active gases; H2O, O3, CO2, CH4,N2O, CFC-11, CFC-12, HCFC-22

Short wave radiation

Ozone

Greenhouse gases

Absorptions by H2O; Briegleb (1992)
Absorptions by O2, O3 and CO2;
Freidenreich and Ramaswamy (1999)
Until 1978; Climatology
From 1979 onward; T42L68 version of MRICCM1 (Shibata et al. 2005)
CO2, CH4, N2O, CFC-11, CFC-12, HCFC-22(historical concentrations)DATA
The observational data adopted for JRA-55 wereprimarily those used in ERA-40 in addition toinformation archived by JMA. The ERA-40
observational dataset was supplied to JMA by
ECMWF for use in JRA-25.
Observations for the period from 1979 onward arebasically the same as those used in JRA-25. Newly
available observational datasets were also collected
and used whenever possible.
Major data source
The ERA-40 observational dataset supplied by ECMWF

Homogenization
RAOBCORE v1.4 (Haimberger et al. 2008) 1958 – 2006
RAOBCORE v1.5 (Haimberger et al. 2012) 2007 – 2012

Reprocessed satellite observations
GMS, GOES-9 and MTSAT-1R (MSC/JMA), METEOSAT(EUMETSAT), TMI (NASA, JAXA), AMSR-E (JAXA),
QuikSCAT(NASA/PO.DAAC), AMI(ESA), GNSS-RO (UCAR)RESULTS
Thanks to a state-of-the art assimilation systemand sophisticated observational data handlingincorporating QC, the JRA-55 datasets generallyshows better quality than other products.

JRA-55 FAMILY
JRA-55C (conventional) and JRA-55AMIP areprovided as unique extra JRA-55 products tohighlight the impacts of observational systems andmodel biases. JRA-55C is suitable for studies ofclimate change and multi-decadal variability
because it is a homogeneous dataset covering an
extended period.

JRA-55: Full observing system reanalysis
JRA-55C: Fixed observing system reanalysis

with conventional observations only, such as surface,radiosonde, tropical cyclone retrieval and windprofiler

JRA-55AMIP: AMIP-type run
without observation assimilation

PRODUCT AVAILABILITY
JRA-55 can be downloaded free from the website
shown below. Near-real-time data are updated
daily on JDDS. JRA-55 provides data on a variety ofphysical elements in GRIB format. Basic JRA-55Cand JRA-55AMIP products are scheduled for releasein the future.

Register to set up an account!
JMA Data Distribution System (JDDS)
http://jra.kishou.go.jp/JRA-55/index_en.html

Data Integration and Analysis System (DIAS)
http://dias-dmg.tkl.iis.u-tokyo.ac.jp/dmm/doc/JRA-55-DIAS-en.html

NCAR

Daily three- and six-hourly data
http://rda.ucar.edu/datasets/ds628.0/

Monthly Means and Variances

http://rda.ucar.edu/datasets/ds628.1/

Fig: Time-series representation of RMS errors in
48-hour forecasts for geopotential height (gpm) at
500 hPa verified against own analysis.
RMS errors are significantly reduced in JRA-55thanks to the application of the latest JMA data
assimilation system.

For more details, see the JRA-55 website
http://jra.kishou.go.jp/JRA-55/index_en.html

Fig: Time-height cross section of equatorial (5°S –5°N) zonal mean U-wind from 1958 to 2012 shownin JRA-55 and JRA-55C. The unit is m/s.
The Quasi-Biennial Oscillation in the lower
stratosphere is apparent in JRA-55C despite thelow number of assimilated observational data.

REFERENCES
JRA-55:
Fig: Frequency of spatial correlation for daily
precipitation over the tropical region (22°S – 22°N)
against TRMM from 1998 to 2009.
JRA-55 shows a higher spatial correlation for daily
precipitation against TRMM observational data
than JRA-25 and ERA-Int.

Kobayashi, S. et al., 2015: The JRA-55 reanalysis: General
specifications and basic characteristics, JMSJ, 93(1), 5-48,
doi:10.2151/jmsj.2015-001.
Ebita, A. et al., 2011: The Japanese 55-year reanalysis "JRA-55":
An interim report, SOLA, 7, 149-152, doi:10.2151/sola.2011-038.

JRA-55C:

Kobayashi, C. et al., 2014: Preliminary results of the JRA-55C, anatmospheric reanalysis assimilating conventional observations
only, SOLA, 10, 78-82, doi:10.2151/sola.2014-016.

CONTACT ADDRESS
Climate Prediction Division, Global Environment andMarine Department, Japan Meteorological Agency.
1-3-4 Otemachi Chiyoda-ku Tokyo, 100-8122, Japan.
Email: jra@met.kishou.go.jp