JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Climate Prediction Division
Global Environment and Marine Department
Japan Meteorological Agency
September 2013

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Change record
Version

Date

Remarks

1.0

30 September 2013

First version

2.0

3 March 2014

Corrected Table 4-1
Added a note to Table 4-2 and Table 4-8
Added B004 to Table 9-1

3.0

20 May 2014

Corrected Table 9-1
Linguistic corrections

4.0

22 May 2015

Added the comprehensive report(Kobayashi et al. 2015) to References

5.0

14 Oct 2015

Added notes to advise not to use cloud work function
and upward mass flux at cloud base in Table 4-12

on

JRA-55

Parameters of isobaric average diagnostic fields(fcst_phy3m125).
6.0

11 Oct 2018

Added B005 and BR05 to Table 9-1

7.0

2 Jul 2021

Changed the climatological
1991-2020 in Chapter 8.

2normalperiodtoJRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data

Contents
1.
2.
3.
4.

Introduction ............................................................................................................... 6File format ................................................................................................................. 6File names .................................................................................................................. 6
Output parameters...................................................................................................... 7
4.1.
1.25-degree latitude/longitude grid data ........................................................... 7
4.1.1. Constant fields (LL125) ............................................................................... 7
4.1.2. Total column analysis fields (anl_column125) ............................................ 7
4.1.3. Isentropic analysis fields (anl_isentrop125) ................................................. 7
4.1.4. Land surface analysis fields (anl_land125) .................................................. 8
4.1.5. Isobaric analysis fields (anl_p125) ............................................................... 8
4.1.6. Snow depth analysis fields (anl_snow125) .................................................. 9
4.1.7. Surface analysis fields (anl_surf125) ........................................................... 9
4.1.8. Total column forecast fields (fcst_column125) .......................................... 10
4.1.9. Land surface forecast fields (fcst_land125)................................................ 10
4.1.10. Isobaric forecast fields (fcst_p125) ........................................................ 10
4.1.11. Two-dimensional average diagnostic fields (fcst_phy2m125) ............... 11
4.1.12. Isobaric average diagnostic fields (fcst_phy3m125) .............................. 12
4.1.13. Land surface average diagnostic fields (fcst_phyland125) .................... 13
4.1.14. Two-dimensional instantaneous diagnostic fields (fcst_surf125) .......... 14
4.1.15. Sea ice fields (ice125)............................................................................. 14
5. Vertical coordinates ................................................................................................. 14
5.1.
Isobaric coordinates ........................................................................................ 14
5.2.
Isentropic coordinates ..................................................................................... 15
6. Physical constants .................................................................................................... 15
7. Monthly statistics..................................................................................................... 15
7.1.
Monthly statistics for fixed hours (Monthly_diurnal) .................................... 15
7.2.
Monthly statistics (Monthly) .......................................................................... 15
8. Climatological normals ........................................................................................... 16
8.1.
Daily mean smooth climatological normals ................................................... 16
8.2.
Monthly mean climatological normals ........................................................... 17
9. Production streams .................................................................................................. 17
10.
Differences from JRA-25 products..................................................................... 18
10.1. Parameter classification .................................................................................. 18
10.2.

Dates in file names ......................................................................................... 193

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
10.3. Parameter additions and changes .................................................................... 19
10.4. Discontinued parameters ................................................................................ 20
10.5. Output interval ................................................................................................ 21
10.6. Vertical coordinates ........................................................................................ 21
10.6.1. Isobaric coordinates ................................................................................ 21
10.6.2. Isentropic coordinates ............................................................................. 21
10.7. Monthly statistics............................................................................................ 21
References ...................................................................................................................... 224

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
List of tables
Table 3-1 Naming convention for historical data. _____________________________________6
Table 3-2 Naming convention for climatological normals. _____________________________6
Table 4-1 Parameters of constant fields (LL125). _____________________________________7
Table 4-2 Parameters of total column analysis fields (anl_column125). _________________7
Table 4-3 Parameters of isentropic analysis fields (anl_isentrop125). ___________________8
Table 4-4 Parameters of land surface analysis fields (anl_land125). ____________________8
Table 4-5 Parameters of isobaric analysis fields (anl_p125). ___________________________9
Table 4-6 Parameter of snow depth analysis fields (anl_snow125). _____________________9
Table 4-7 Parameters of surface analysis fields (anl_surf125). _________________________9
Table 4-8 Parameters of total column forecast fields (fcst_column125). _______________ 10
Table 4-9 Parameters of land surface forecast fields (fcst_land125). __________________ 10
Table 4-10 Parameters of isobaric forecast fields (fcst_p125). ________________________ 11
Table 4-11 Parameters of two-dimensional average diagnostic fields (fcst_phy2m125). _ 12
Table 4-12 Parameters of isobaric average diagnostic fields (fcst_phy3m125). _________ 13
Table 4-13 Parameters of land surface average diagnostic fields (fcst_phyland125). ____ 13
Table 4-14 Parameters of two-dimensional instantaneous diagnostic fields (fcst_surf125).
_________________________________________________________________________________ 14
Table 4-15 Parameter of sea ice fields (ice125). _____________________________________ 14
Table 6-1 Physical constants. _____________________________________________________ 15
Table 7-1 Time range indicator for monthly statistics. ______________________________ 16
Table 9-1 Production streams of JRA-55. __________________________________________ 18
Table 10-1 Example of category change (for anl_p). _________________________________ 19
Table 10-2 Example of category change (for fcst_phy2m). ___________________________ 19
Table 10-3 Example of file name date change (for fcst_phy2m.1981010100).___________ 19
Table 10-4 Discontinued parameters in isobaric analysis fields (anl_chipsi). __________ 20
Table 10-5 Discontinued parameter in isentropic analysis fields (anl_isentrop). _______ 20
Table 10-6 Discontinued parameters intwo-dimensional diagnostic fields (fcst_phy2m). 20
Table 10-7 Discontinued parameters in three-dimensional diagnostic fields (fcst_phy3m).
_________________________________________________________________________________ 21
Table 10-8 Discontinued parameter in land surface diagnostic fields (fcst_phyland). ___ 21

5

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data

1. Introduction
This handbook gives an overview of products stemming from the Japanese 55-year
Reanalysis (JRA-55) project conducted by the Japan Meteorological Agency (JMA) forthe period from 1958 onward (Kobayashi et al. 2015), and also outlines how theseproducts differ from the corresponding JRA-25 versions (Onogi et al. 2007).

2. File format
Both daily and monthly data are encoded in Gridded binary (GRIB) Edition 1 format(WMO 2011). (Daily data include 3-, 6- and 24-hourly data, which vary by category).

3. File names
JRA-55 product file names follow the naming convention shown in Table 3-1 forhistorical data and that shown in Table 3-2 for climatological normals.
Table 3-1

Naming convention for historical data.

Time range
Daily

M onthly_diurnal

M onthly

Table 3-2

Type

Filename

2D fields<category>.<year><month><day><hour>

3D fields<category>_<parameter>.<year><month><day><hour>

2D fields, average<category>.<year><month>_<hour>

2D fields, variance<category>_var.<year><month>_<hour>

3D fields, average<category>_<parameter>.<year><month>_<hour>

3D fields, variance<category>_<parameter>_var.<year><month>_<hour>

2D fields, average<category>.<year><month>2D fields, variance<category>_var.<year><month>

3D fields, average<category>_<parameter>.<year><month>

3D fields, variance<category>_<parameter>_var.<year><month>

Naming convention for climatological normals.

Time range
Daily
M onthly_diurnal
M onthlyType

Filename

2D fields<category>.clim<period>.day<month><day>

3D fields<category>_<parameter>.clim<period>.day<month><day>

2D fields, average<category>.clim<period>.mon<month>

3D fields, average<category>_<parameter>.clim<period>.mon<month>6

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data

4. Output parameters4.1. 1.25-degree latitude/longitude grid data
4.1.1. Constant fields (LL125)
Table 4-1 shows the parameters of constant fields.
Table 4-1

Parameters of constant fields (LL125).

CodefigureField parameterUnit

6 Geopotential

m2 s-281 Land cover (1=land, 0=sea)

Proportion

4.1.2. Total column analysis fields (anl_column125)
Total column analysis fields (Table 4-2) are produced by integrating the corresponding
analyzed fields vertically from the bottom to the top of the atmosphere. These fields are
output every six hours at 00, 06, 12 and 18 UTC.
Table 4-2

Parameters of total column analysis fields (anl_column125).

CodefigureField parameter

Unit

54 Precipitable waterkg m-2152 M eridional water vapour flux

kg m-1 s-1

157 Zonal water vapour flux

kg m-1 s-1+

190 Zonal thermal energy flux

W m-1

191 M eridional thermal energy flux+

W m-1+ See Section 10.3 “Parameter additions and changes”

Note: Precipitable water contains water vapour only.

4.1.3. Isentropic analysis fields (anl_isentrop125)
The parameters shown in Table 4-3 are vertically interpolated to the isentropic
surfaces listed in Section 5.2 except specific humidity, which is interpolated to 14 levels
from 270 to 400 K only. These fields are output every six hours at 00, 06, 12 and 18 UTC.

7

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 4-3

Parameters of isentropic analysis fields (anl_isentrop125).

CodefigureField parameter

Unit

1 Pressure+

FilenamePa

anl_isentrop125_pres2-1

4 Potential vorticity

K m kg s

7 Geopotential heightgpm

33 u-component of wind
34 v-component of wind
37 M ontgomery stream function
51 Specific humidity
132 Square of Brunt-Vaisala frequency

anl_isentrop125_pvor
anl_isentrop125_hgt

ms-1

anl_isentrop125_ugrd

ms-1

anl_isentrop125_vgrd

2-2

anl_isentrop125_mntsf

Pa s

-1

anl_isentrop125_vvel

-1

kg kg

anl_isentrop125_spfh-2

anl_isentrop125_bvf2

m s

39 Vertical velocity-1s+ See Section 10.3 “Parameter additions and changes”

4.1.4. Land surface analysis fields (anl_land125)
The parameters shown in Table 4-4 are output from land surface analysis every six
hours at 00, 06, 12 and 18 UTC.
Table 4-4

Parameters of land surface analysis fields (anl_land125).

CodefigureField parameter

Unit

Level

65 Water equivalent of accumulated snow depth

kg m-2Ground surface

144 Canopy temperature

K

Ground surface

145 Ground temperature

K

85 Soil temperature

K

225 Soil wetness

Proportion

Ground surface
Entire soil(considered as a single layer)
Underground layers

4.1.5. Isobaric analysis fields (anl_p125)
The parameters shown in Table 4-5 are vertically interpolated to the isobaric surfaces
listed in Section 5.1 except dew-point depression (or deficit), specific humidity andrelative humidity, which are interpolated to 27 levels from 1000 to 100 hPa only. These
fields are produced every six hours at 00, 06, 12 and 18 UTC.

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JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 4-5

Parameters of isobaric analysis fields (anl_p125).

CodefigureField parameter

Unit

Filename

7 Geopotential heightgpm

anl_p125_hgt

11 TemperatureK

anl_p125_tmp

18 Dew-point depression (or deficit)

K

anl_p125_depr

ms-1

anl_p125_ugrd

ms-1

anl_p125_vgrd

2

m s

-1

anl_p125_strm

2-1

anl_p125_vpot

39 Vertical velocity

Pa s

-1

anl_p125_vvel

43 Ralative vorticitys-1

anl_p125_relv

44 Relative divergences-1

anl_p125_reld

51 Specific humidity

kg kg-1

anl_p125_spfh%

anl_p125_rh

33 u-component of wind
34 v-component of wind
35 Stream function
36 Velocity potential

52 Relative humiditym s++ See Section 10.3 “Parameter additions and changes”

4.1.6. Snow depth analysis fields (anl_snow125)
The parameter shown in Table 4-6 is output from snow depth analysis at 18 UTC every
day.
Table 4-6

Parameter of snow depth analysis fields (anl_snow125).

CodefigureField parameter

Unit

66 Snow depth

m

Level
Ground surface

4.1.7. Surface analysis fields (anl_surf125)
Surface analysis fields (Table 4-7) are produced every six hours at 00, 06, 12 and 18
UTC.
Table 4-7

Parameters of surface analysis fields (anl_surf125).

CodefigureField parameter

Unit

Level

1 Pressure

Pa

Ground or water surface

2 Pressure reduced to M SLPa

M ean sea level

11 Temperature

K2m

13 Potential temperature

K

Ground or water surface

18 Dew-point depression (or deficit)

K

2m
-1

51 Specific humidity

kg kg

2m

52 Relative humidity%

2m

33 u-component of wind
34 v-component of wind

ms

-1

10m

ms

-1

10m

Note: The order of the parameters in monthly statistics and climatological normal files differs from that in daily files(Table 4-7), 1, 13, 2, 11, 18, 51, 52, 33 and 34.

9JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data

4.1.8. Total column forecast fields (fcst_column125)
Total column forecast fields (Table 4-8) are produced every three hours, integrating
vertically from the bottom to the top of the atmosphere three-hour forecast fields at 03,
09, 15 and 21 UTC, and six-hour forecast fields at 00, 06, 12 and 18 UTC.
Table 4-8

Parameters of total column forecast fields (fcst_column125).

CodefigureField parameter

Unit

10 Total ozone

Dobson54 Precipitable waterkg m-258 Cloud ice+kg m-2152 M eridional water vapour flux*

kg m-1 s-1

157 Zonal water vapour flux*

kg m-1 s-1+

190 Zonal thermal energy flux

W m-1

191 M eridional thermal energy flux+

W m-1

227 Cloud liquid water+kg m-2+, * See Section 10.3 “Parameter additions and changes”

Note: Precipitable water contains water vapour only.

4.1.9. Land surface forecast fields (fcst_land125)
Land surface forecast fields (Table 4-9) are produced every three hours at 00, 03, 06,
09, 12, 15, 18 and 21 UTC.
Table 4-9

Parameters of land surface forecast fields (fcst_land125).

CodefigureField parameter

Unit

65 Water equivalent of accumulated snow depth+Level

kg m-2Ground surface

66 Snow depthmGround surface

144 Canopy temperature

K

Ground surface

145 Ground temperature

K

Ground surface

223 M oisture storage on canopymGround surface

224 M oisture storage on ground/coverm

85 Soil temperature

K
Proportion

Ground surface
Entire soil(considered as a single layer)
Underground layers

kg m-3

Underground layers+

225 Soil wetness ++226 M ass concentration of condensed water in soil
+ See Section 10.3 “Parameter additions and changes”

4.1.10. Isobaric forecast fields (fcst_p125)
The parameters shown in Table 4-10 are vertically interpolated to the isobaric surfaces
listed in Section 5.1 except cloud cover, cloud water, cloud liquid water and cloud ice,
which are interpolated to 27 levels from 1000 to 100 hPa only. These fields are output
every six hours at 00, 06, 12 and 18 UTC.

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JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 4-10

Parameters of isobaric forecast fields (fcst_p125).

CodefigureField parameter

Unit

Filename

71 Cloud cover+%

221 Cloud waterkg kg-1

fcst_p125_cwat-1

fcst_p125_clwc-1

fcst_p125_ciwc-1fcst_p125_ozone+

228 Cloud liquid water

fcst_p125_tcdc

kg kg

+

229 Cloud ice

kg kg

237 Ozone mixing ratio+

mg kg+ See Section 10.3 “Parameter additions and changes”

4.1.11. Two-dimensional average diagnostic fields (fcst_phy2m125)
Two-dimensional average diagnostic fields are produced every three hours. The
parameters shown in Table 4-11 are averaged from the beginning of forecasts up to threehours for 00 - 03, 06 - 09, 12 - 15 and 18 - 21 UTC, and from three to six hours for 03 06, 09 - 12, 15 - 18 and 21 - 24 UTC.
Dates in file names indicate the beginning of the averaging period.

11JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 4-11

Parameters of two-dimensional average diagnostic fields (fcst_phy2m125).

CodefigureField parameter

Unit

1 Pressure

Pa

57 Evapolation+
61 Total precipitation+

62 Large scale precipitation
63 Convective precipitation
64 Snowfall rate water equivalent
121 Latent heat flux

Ground or water surface

mm day-1

Ground or water surface

mm day-1

Ground or water surface

mm day-1

Ground or water surface

mm day-1

Ground or water surface

mm day-1

Ground or water surface-2

Ground or water surface-2

Wm

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Ground or water surface-2

Nominal top of atmosphere-2Nominal top of atmosphere-2Nominal top of atmosphere-2Nominal top of atmosphere-2Nominal top of atmosphereWm

122 Sensible heat flux
124 M omentum flux, u component

Nm

125 M omentum flux, v component

Nm

147 Zonal momemtum flux by long gravity wave

Nm

148 M eridional momemtum flux by long gravity wave
154 M eridional momemtum flux by short gravity wave
159 Zonal momemtum flux by short gravity wave

Nm
Nm
Nm

160 Clear sky upward solar radiation flux

Wm

161 Clear sky downward solar radiation flux

Wm

163 Clear sky downward long wave radiation flux

Wm

204 Downward solar radiation flux

Wm

205 Downward long wave radiation flux

Wm

211 Upward solar radiation flux

Wm

212 Upward long wave radiation flux

Wm

160 Clear sky upward solar radiation flux

Wm

162 Clear sky upward long wave radiation flux

Wm

204 Downward solar radiation flux

Wm

211 Upward solar radiation flux

Wm

212 Upward long wave radiation flux

Level

Wm

+ See Section 10.3 “Parameter additions and changes”

4.1.12. Isobaric average diagnostic fields (fcst_phy3m125)
Isobaric average diagnostic fields are produced every six hours. The parameters shownin Table 4-12 are averaged from the beginning of forecasts up to six hours for 00 - 06, 06- 12, 12 - 18 and 18 - 24 UTC, and vertically interpolated to the isobaric surfaces listed in
Section 5.1.
Dates in file names indicate the beginning of the averaging period.

12JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 4-12

Parameters of isobaric average diagnostic fields (fcst_phy3m125).

CodefigureField parameter

Unit

146 Cloud work function#

Filename

J kg-1

fcst_phy3m125_cwork-1

151 Adiabatic zonal accelerationm s day-1

fcst_phy3m125_adua

165 Adiabatic meridional acceleration

m s-1 day -1

fcst_phy3m125_adva

173 Gravity wave zonal acceleration
174 Gravity wave meridional acceleration-1

m s day-1

fcst_phy3m125_gwdua-1-1

fcst_phy3m125_gwdva

m s day-1

222 Adiabatic heating rate

K day

230 Upward mass flux at cloud base##

kg m-2 s-1

fcst_phy3m125_adhr
fcst_phy3m125_mflxb-2 -1

231 Upward mass flux

fcst_phy3m125_mflux

kg m s-1

236 Adiabatic moistening rate

kg kg day-1

-1

fcst_phy3m125_admr

239 Convective zonal accelerationm s day-1

fcst_phy3m125_cnvua

240 Convective meridional acceleration

m s-1 day -1

fcst_phy3m125_cnvva

241 Large scale condensation heating rate
242 Convective heating rate

K day

-1

K day

-1

fcst_phy3m125_lrghr
fcst_phy3m125_cnvhr-1

243 Convective moistening rate

kg kg day

246 Vertical diffusion heating rate

K day -1

247 Vertical diffusion zonal acceleration
248 Vertical diffusion meridional accelerationm s day

-1

-1

-1

-1

249 Vertical diffusion moistening rate

kg kg day

250 Solar radiative heating rate

K day -1

251 Longwave radiative heating rate

K day

fcst_phy3m125_vdfua
fcst_phy3m125_vdfva-1kg kg dayfcst_phy3m125_vdfmr
fcst_phy3m125_swhr-1-1

253 Large scale moistening rate

fcst_phy3m125_cnvmr
fcst_phy3m125_vdfhr-1m s day-1

fcst_phy3m125_lwhr-1

fcst_phy3m125_lrgmr#, ## Cloud work function and upward mass flux at cloud base are variables that are used for computation in the cumulus

convection scheme, and does not represent the atmospheric state. Therefore, when vertically interpolated to the isobaric
surfaces, those variables lose their physical meaning. Please discard those data.

4.1.13. Land surface average diagnostic fields (fcst_phyland125)
Land surface average diagnostic fields are produced every three hours. The parameters
shown in Table 4-13 are averaged from the beginning of forecasts up to three hours for 00- 03, 06 - 09, 12 - 15 and 18 - 21 UTC, and from three to six hours for 03 - 06, 09 - 12, 15- 18 and 21 - 24 UTC.
Dates in file names indicate the beginning of the averaging period.
Table 4-13

Parameters of land surface average diagnostic fields (fcst_phyland125).

CodefigureField parameter

Unit

Level

90 Water run-off

mm day -1

Ground surface

155 Ground heat flux

-2

Ground surface-2

Ground surface-2

Ground surface
The bottom of land surface
model

Wm

202 Evapotranspiration

Wm

203 Interception loss

Wm

90 Water run-off+mm day -1

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JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
+ See Section 10.3 “Parameter additions and changes”

4.1.14. Two-dimensional(fcst_surf125)

instantaneous

diagnostic

fields

Two-dimensional instantaneous diagnostic fields (Table 4-14) are produced every
three hours at 00, 03, 06, 09, 12, 15, 18 and 21 UTC.
Table 4-14

Parameters of two-dimensional instantaneous diagnostic fields (fcst_surf125).

CodefigureField parameter

Unit

Level

1 Pressure

Pa

Ground or water surface

83 Surface roughnessmGround or water surface

118 Brightness temperature+

K

Ground or water surface%

90 - 1100 hPa%

90 - 500 hPa

74 M edium cloud cover%

500 - 850 hPa

73 Low cloud cover*%

850 - 1100 hPa

2 Pressure reduced to M SLPa

M ean sea level

11 Temperature

K

2m

18 Dew-point depression (or deficit)

K*

71 Total cloud cover*

75 High cloud cover

*

2m
-1

51 Specific humidity

kg kg

2m

52 Relative humidity%

2m

33 u-component of wind
34 v-component of wind

ms

-1

10m

ms

-1

10m

+, * See Section 10.3 “Parameter additions and changes”

4.1.15. Sea ice fields (ice125)
Sea ice fields (Table 4-15) are output every three hours.
Table 4-15
CodefigureParameter of sea ice fields (ice125).
Field parameter

Unit

91 Ice cover (1 = ice, 0 = no ice)

Proportion

5. Vertical coordinates
5.1. Isobaric coordinates
Isobaric fields are produced for 37 isobaric surfaces (1000, 975, 950, 925, 900, 875,
850, 825, 800, 775, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 225, 200, 175,
150, 125, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2 and 1 hPa) except dew-point depression (or14JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
deficit), specific humidity, relative humidity, cloud cover, cloud water, cloud liquid waterand cloud ice, which are produced for 27 levels from 1000 to 100 hPa only.

5.2. Isentropic coordinates
Isentropic fields are produced for 21 isentropic surfaces (270, 280, 290, 300, 310, 320,
330, 340, 350, 360, 370, 380, 390, 400, 425, 450, 475, 550, 650, 750 and 850 K) except
specific humidity, which is produced for 14 levels from 270 to 400 K only.

6. Physical constants
The fundamental physical constants used in the forecast model are as follows:
Table 6-1

Physical constants.
Quantity

Value

Stefan-Boltzmann constant σ

5.67 x 10-8 W m-2 K-4

Earth's radius

6.371 x 106 m

Angular speed of Earth's rotation

7.29245 x 10-5 rad s -1

Gravitational acceleration

9.80665 m s -2

Gas constant for dry air

287.04 J K-1 kg-1

Specific heat of dry air at constant pressure c p1004.6 J K-1 kg-1

Latent heat of vaporization

2.507 x 106 J kg-1

Solar constant1365 W m-2

7. Monthly statistics
7.1. Monthly statistics for fixed hours (Monthly_diurnal)
Monthly averages and variances are produced for each of the output hours at 00, 06, 12
and 18 UTC (and 03, 09, 15 and 21 UTC when available), and are referred to as monthly
statistics for fixed hours (Monthly_diurnal).
Table 7-1 shows the meanings of the time range indicator encoded in Octet 21 ofSection 1.

7.2. Monthly statistics (Monthly)
Averages and variances for the whole month are also produced using only six-hourly
data for analyzed and instantaneous forecast fields and averages from the beginning of
forecasts up to six hours for average diagnostic fields. These statistics are referred to as
monthly statistics (Monthly).

15

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 7-1 shows the meanings of the time range indicator encoded in Octet 21 ofSection 1.
Table 7-1

Time range indicator for monthly statistics.

Code
M eaning
figure113 Average of N forecasts (or initialized analyses); each product has forecast period of P1 (P1 = 0
for initialized analyses); products have reference times at intervals of P2, beginning at the givenreference time
123 Average of N uninitialized analyses, starting at the reference time, at intervals of P2
128 Average of N forecast products with a valid time ranging between reference time + P1 andreference time + P2; products have reference times at Intervals of 24 hours, beginning at thegiven reference time
129 Temporal variance of N forecasts; each product has valid time ranging between reference time
+ P1 and reference time + P2; products have reference times at intervals of 24 hours, beginningat the given reference time; unit of measurement is square of that in Code Table 2
130 Average of N forecast products; each product has a forecast period from P1 to P2; products
have reference times at intervals of P2 - P1, beginning at the given reference time; thus the N
products cover a continuous time span.
131 Temporal variance of N forecasts; valid time of the first product ranges between R + P1 and R+ P2, where R is reference time given in octets 13 to 17, then subsequent products have valid
time range at interval of P2 – P1; thus all N products cover continuous time span; products
have reference times at intervals of P2 - P1, beginning at the given reference time; unit ofmeasurement is square of that in Code Table 2
132 Temporal variance of N uninitialized analyses (P1 = 0) or instantaneous forecasts (P1 > 0);each product has valid time at the reference time + P1; products have reference times atintervals of P2, beginning at the given reference time; unit of measurement is square of that in
Code Table 2

8. Climatological normals
Climatological normals have been calculated for the period from 1991 to 2020 using
the methods described below.

8.1. Daily mean smooth climatological normals
This calculation involves two steps. In the first, daily values are computed using
six-hourly values for analysis and instantaneous forecast fields and averages from the
beginning of forecasts up to six hours for average diagnostic fields, and a simple
average is then taken for the base period for each day of the year except leap days. In
the second, Lanzcos low-pass filtering (Duchon 1979) with 121-term weight factors anda 60-day cutoff is applied to the time sequence of daily values to treat thehigh-frequency variation remaining in the daily values calculated in the first step.
Climatological normals for leap days are derived by averaging the smoothclimatological normals for 28th February and 1st March.

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JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
The concept of this method is quite simple. It should be noted that monthly means
calculated from daily means do not coincide with those outlined above due to thedifference in treatment for leap days and the presence or absence of filtering.

8.2. Monthly mean climatological normals
Monthly mean climatological normals are calculated by simply averaging historicalmonthly mean values.

9. Production streams
The JRA-55 production was organized into several streams as shown in Table 9-1 inorder to shorten the time taken. Separate stream names are also assigned for cases inwhich data assimilation cycles were rerun or secondary products were recalculated.
These stream names are encoded in Octets 46 - 49 of Section 1.
There are three discontinuities among the streams in Table 9-1 at 00 UTC on 1 July
1958 (A003/A002), 00 UTC on 1 September 1980 (A004/B002) and 00 UTC on 1
October 1992 (B003/B002). For other stream changeovers, subsequent streams were
initiated from the last data of the preceding streams.

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Table 9-1

Production streams of JRA-55.

StreamPeriodSection 1
Octets
46-49
AE03

A003

A002

A004

B002

B003

until
30 Jun 1958

AR03
A003

other parameters

A002

same as AE03
same as AR03, and
anl_isentrop (until 31 Dec 1972)
other parameters

1 Dec 1974
to
31 Aug 1980

AE04

same as AE03

AR04

same as AR03

A004

other parameters

1 Sep 1980
to31 May 1987

BE02

same as AE03

BR02

same as AR03, and anl_isentrop

B002

other parameters

BE03

same as AE03

BR03

same as AR03

B003

other parameters

BE02

same as AE03, but until 31 Dec 2012
same as AR03, but until 31 Dec 2012, and
anl_isentrop (until 31 Jan 2000)
other parameters

1 Jul 1958
to30 Nov 1974

1 Jun 1987
to30 Sep 1992

AR02

BR02

B004

1 Jan 2014
to3 Jun 2018
18UTC

B004

B005

3 Jun 2018
21UTC
onward10.

fcst_column125 (thermal energy fluxes)
fcst_p125 (cloud liquid water, cloud ice, ozone mixing ratio)
fcst_phy3m125
anl_isentrop125
fcst_column125 (other than thermal energy fluxes)
fcst_phy2m125
fcst_surf125 (surface roughness, brightness temperature)

AE02

1 Oct 1992
to
31 Dec 2013

B002

Note

B002

BR05

fcst_surf125 (from 4 Jun 2018 to 7 Oct 2018)

B005

other parameters

Differences from JRA-25 products

10.1. Parameter classification
JRA-25 products contained categories in which two- and three-dimensional fields were
put together. These are output into separate categories in JRA-55 products, and files ofthree-dimensional fields are divided into individual parameters except land surface fields.

18JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 10-1

Example of category change (for anl_p).

JRA-25JRA-55Isobaric analysis fields
anl_p125_hgt (geopotential height)
anl_p125_tmp (temperature)

anl_p

…
Surface analysis fields
anl_surf125

JRA-25 products contained categories in which instantaneous, average and extreme
fields were put together. These are output into separate categories in JRA-55 products.
Table 10-2

Example of category change (for fcst_phy2m).

JRA-25JRA-552-dimensional average diagnostic fields
fcst_phy2m

fcst_phy2m2-dimensional instantaneous diagnostic fields
fcst_surf
2-dimensional extreme fields 1
minmax_surf

1Extreme fields are produced for daily model grid data only; they are not produced for monthly statistics orlatitude/longitude grid data.

10.2. Dates in file names
In JRA-25 products, dates in file names indicated valid times for instantaneous fields
and the end of the averaging period for average diagnostic fields. In JRA-55 products,
dates in file names indicate the beginning of the averaging period.
Table 10-3

Example of file name date change (for fcst_phy2m.1981010100).
Valid timeJRA-25from 18UTC on 31 Dec 1980 to 00UTC 1 Jan 1981

JRA-55from 00 to 03UTC on 1 Jan 1981

10.3. Parameter additions and changes
Parameters added to JRA-55 products are indicated by a superscript + in the parameter
tables of Chapter 4.
Some parameters have been switched from average forecast fields to instantaneous
forecast fields in JRA-55 products. These are indicated by a superscript *.

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10.4. Discontinued parameters
Table 10-4

Discontinued parameters in isobaric analysis fields (anl_chipsi).

Code
Field parameter
figure35 Stream function

Unit

Level

m2 s-1

10m

36 Velocity potential

2 -1

m s

10m

43 Ralative vorticity

s

-1

10m

s

-1

10m

44 Relative divergence
Table 10-5

Discontinued parameter in isentropic analysis fields (anl_isentrop).

CodefigureField parameter

Unit

11 Temperature

Table 10-6

K

Discontinued parameters intwo-dimensional diagnostic fields (fcst_phy2m).

Code
Field parameter
figure2 Pressure reduced to M SL (mean)

Unit
Pa

Level
M ean sea level

ms

-1

10m

137 v-component of wind (mean, surface)

ms

-1

10m

138 Temperature (mean, surface)K

136 u-component of wind (mean, surface)2m-1

139 Specific humidity (mean, surface)

kg kg

2m

80 Water temperature#

K

Water surface

218 M oist process heating rate

W m-2

168 Frequency of precipitation%

169 Frequency of cumulus precipitation%

200 Zonal temperature flux

K Pa m s-1

201 M eridional temperature flux

K Pa m s-1

219 M aximum wind speed

m s-1

Entire atmosphere(considered as a single layer)
Ground or water surface

Lowermost hyblid level-1

220 M aximum hourly precipitation

Ground or water surface
Entire atmosphere(considered as a single layer)
Entire atmosphere(considered as a single layer)

mm hour

Ground or water surface

Entire atmosphere(considered as a single layer)# In JRA-55 products, SST is output as brightness temperature in the Two-dimensional instantaneous diagnostic fields(fcst_surf125).
kg m-276 Cloud water20

JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
Table 10-7

Discontinued parameters in three-dimensional diagnostic fields (fcst_phy3m).

CodefigureField parameter

Unit

76 Cloud waterkg m-2175 Geopotential height (mean)gpm

176 u-component of wind (mean)m s-1

177 v-component of wind (mean)m s-1

178 Vertical velocity (mean)

Pa s-1179 Temperature (mean)K

180 Specific humidity (mean)

kg kg-1

Table 10-8
CodefigureDiscontinued parameter in land surface diagnostic fields (fcst_phyland).
Field parameter

86 Soil moisture content

Unit

Level

Proportion

Underground layers

10.5. Output interval
Most JRA-25 products were output at six-hourly intervals. In JRA-55 products, land
surface and two-dimensional forecast fields are output at three-hourly intervals.

10.6. Vertical coordinates
10.6.1. Isobaric coordinates
In JRA-25 products, isobaric fields were produced for 23 isobaric surfaces (1000, 925,
850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2, 1 and 0.4hPa). In JRA-55 products, they are produced for the 37 isobaric surfaces listed in Section
5.1 (975, 950, 900, 875, 825, 800, 775, 750, 650, 550, 450, 350, 225, 175 and 125 hPa
have been added, and 0.4 hPa has been omitted).

10.6.2. Isentropic coordinates
In JRA-25 products, isentropic fields were produced for 20 isentropic surfaces (270,280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 425, 450, 475, 550, 650
and 750 K). In JRA-55 products, they are produced for the 21 isentropic surfaces listed in
Section 5.2 (850 K has been added).

10.7. Monthly statistics
Monthly statistics for JRA-25 products were saved in 4-byte big-endian floating point
format. For JRA-55 products, they are saved in GRIB Edition 1 format (WMO 2011) inthe same way as daily data.

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JRA-55 Product Users' Handbook
1.25-degree latitude/longitude grid data
While only monthly averages were produced in JRA-25 products, variances are also
produced in JRA-55 products except for land surface and two-dimensional averagediagnostic fields. Variance files are indicated by “_var” at the end of file names (Table
3-1).

References
Duchon, C. E. (1979). Lanczos filtering in one and two dimensions. J. Appl. Meteor., 18,1016-1022.
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”: aninterim report. SOLA, 7, 149-152. (This article is an interim report of JRA-55 asof 2011. Please refer Kobayashi et al. (2015) for the JRA-55 comprehensive
report.).
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.
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.
WMO.
(2011).
Manual
on
codes
I.2.
Retrievedfrom
http://www.wmo.int/pages/prog/www/WMOCodes/WMO306_vI2/VolumeI.2.ht
ml22