Specifications (as of 31 December 2020) – an excerpt from the Joint WMO Technical Progress
Report on the Global Data Processing and Forecasting System and Numerical Weather Prediction
Research Activities for 2020
4.7

Long range forecasts (LRF) (30 days up to two years)

4.7.1

Models

4.7.1.1 In operation
JMA operates its Seasonal Ensemble Prediction System (Seasonal EPS; JMA/MRI-CPS2) using acoupled atmosphere-ocean model. The current system was upgraded in June 2015. The 51-member
ensemble is used for the three-month forecast issued every month and for the warm/cold season
forecasts issued five times a year (in February, March, April, September and October). The El Niño
outlook is also issued based on the same model results.
The JMA/MRI-CPS2 was developed by JMA including the Meteorological Research Institute (MRI).
Its specifications are shown in Table 4.7.1.1-1.
4.7.1.2 Research performed in this field
JMA plans to upgrade the Seasonal EPS in February 2022. The new system, JMA/MRI-CPS3, will
incorporate a wide range of research progress achieved at JMA and MRI (Table 4.7.1.1-1). The
atmospheric model is from GSM2003, with additional improvements such as cloud and cumulus
convection schemes (referred to here as GSM2003C). Atmospheric conditions are initialized with JRA-3Q
for reforecasts, and Global Analysis (GA) allowing faster atmospheric update is also used in the operation
to broaden its scope toward sub-seasonal forecasts. Land is initialized separately from this analyses, due
to inconsistencies in lake/land treatment in the model, including GSM2003C’s newly-developed lake
scheme requiring initialization. To this end, the model’s off-line land surface simulation will be used.
Ocean and sea ice initial conditions are taken from MOVE/MRI.COM-G3 (see 4.5.1.1 (1) *), but withdownscaling into the eddy-permitting ocean resolution (0.25 by 0.25°in longitude and latitude). The EPS
will feature a combination of LAF and initial perturbation as with previous system. Five-member
ensemble predictions are made every day, and atmospheric initial perturbations for each initial date are
obtained using the BGM. Ocean initial perturbations are calculated using the 4DVAR minimization
history to approximate the day’s analysis error covariance.

* See Joint WMO Technical Progress Report on the Global Data Processing and Forecasting System
and Numerical Weather Prediction Research Activities for 2020.
4.7.2

Operationally available EPS LRF products

JMA provides gridded data and map products for three-month forecasts every month. Warm-season(June-July-August; JJA) forecasts are issued in February, March and April, and cold-season(December-January-February; DJF) forecasts are issued in September and October.
A model systematic bias was estimated for use as an average forecast error calculated from hindcast
experiments for the 30 years from 1981 to 2010. The bias is removed from geopotential height, sea-1-level pressure, temperature, and sea surface temperature in advance to produce ensemble forecast
products such as ensemble means and spreads.
The following model output products for three-month, warm/cold-season (Tables 4.7.2-1, 4.7.2-2 and4.7.2-3) and six-month (Tables 4.7.2-1) forecasts are provided via the Tokyo Climate Center (TCC)
website (https://ds.data.jma.go.jp/tcc/tcc/index.html).

Table 4.7.1.1-1 Seasonal EPS specifications
1.system
System Name

JMA/MRI-CPS2JMA/MRI-CPS3

Operation startJune 2015

February 2022

Model version

GSM1011C

GSM2003C

Resolution

Global TL159 reduced
Gaussian grid (~110km)

Global TL319 reduced
Gaussian grid (~55 km)

Vertical levels(model top)

60 levels (0.1 hPa)

100 levels (0.01 hPa)

Model version

MRI.COM v3.2

MRI.COM v4.6

Horizontal
resolution

1 (longitude) × 0.3-0.5˚(latitude)

0.25 (longitude) × 0.25˚(latitude)

Vertical levels

52 levels with a bottom
boundary layer

60 levels

2.configuration

Atmospheric
model

Oceanic model

Forecast period

7 monthsForecast frequency

13 ensemble members every
5 days5 ensemble members every day

AtmosphereJRA-55JRA-3Q ( hindcasts + forecasts)
the Global Analysis (GA;forecasts only)

Land Surface

JRA-55Off-line model runs forced by
JRA-3Q and GA

Ocean

MOVE/MRI.COM-G2(3DVAR)

MOVE/MRI.COM-G3(Low-res. 4DVAR+High-res
downscaling)

Initialconditions

Sea ice

Ensemble
generation
methodInitial condition
perturbation

Breeding of growing mode
(BGM)
The Lagged Average
Forecast (LAF)

Modelperturbation(atmosphere)

A stochastic physics scheme-2-MOVE/MRI.COM-G3(3DVAR)
BGM for the atmosphere
Ocean perturbations calculatedusing 4DVAR minimization
history
LAF method

Hindcast

PeriodTwo initial dates per monthfor the 36 years from 1979 to2014

Ensemble size

Five for each initial date

Two initial dates per month forthe 30 years from 1991 to 2020

Table 4.7.2-1 Gridded data products (GRIB2) for three-month, warm/cold-season and sixmonth forecasts provided via the TCC website
Details
Level
Area
Base time &(hPa)forecast time
Ensemblemean,
itsanomaly, andspread(standarddeviation)
valuesof
forecast
membersIndividual
ensemblemembers

Sea level pressure*,
its anomaly and spread
Daily mean precipitation,
its anomaly and spread
Sea surface temperature*and its anomaly
Temperature*, its anomaly
and spread
Geopotential height*, its
anomaly and spread
Wind (u, v), its anomaly andspread
Sea level pressure* and its
anomaly
Daily mean precipitationand its anomaly
Sea surface temperature*and its anomaly
Temperature*anditsanomaly
Relative humidity and its
anomaly
Specific humidity and its
anomaly (only for threemonthandwarm/coldseason forecasts)Geopotential height* and its
anomaly
Wind (u, v) and its anomaly

Surf, 850
500
850, 200
Surf, 850, 500, 200
850

Global2.5˚ ×2.5˚Base time:
00 UTC around the15th of each month(three-monthandwarm/coldseason
forecasts) and 00UTC
every 5 days (sixmonth forecasts)
Forecast times:
Oneandthreemonth averages fortargeted terms
Base time:
00 UTC on each
initialdateofprediction(every 5 days)
Forecast times:
One-month averages
for targeted terms

850

850, 500, 300,200, 100
850, 500, 200* Geopotential height, sea level pressure, temperature and sea surface temperature are calibrated
by subtracting the systematic error from the direct model output.
Table 4.7.2-2 Map products for three-month and warm/cold-season forecasts provided via theTCC website<https://ds.data.jma.go.jp/tcc/tcc/products/model/map/4mE/index.html>
Ensemblemean,
itsanomaly andspread

Forecast timeThree-month forecast:
Averages of first month,secondmonth,
thirdmonth, and three months
Warm/cold season forecast:
Averages of three months(JJA or DJF)

Parameter
Geopotential height at 500 hPa, related anomaly andspread
Temperature at 850 hPa, its anomaly and spread
Sea level pressure, its anomaly and spread
Stream function at 200 hPa, its anomaly and spread
Stream function at 850 hPa, its anomaly and spread
Wind (u, v) anomaly at 850 hPa
Velocity potential at 200 hPa, its anomaly and spread-3-

Precipitation, its anomaly and spread
Temperature at 2 m, its anomaly and spread
Sea surface temperature and its anomaly

Table 4.7.2-3 SST Index Time Series<https://ds.data.jma.go.jp/tcc/tcc/products/model/indices/3-mon/indices1/shisu_forecast.php>
Index
NINO.1+2
NINO.3
NINO3.4
NINO.4NINO.WEST
TNATSA
TAD
IOBW
WTIO
SETIO
IOD

Description
Region off coasts of Peru andChile
Eastern/Central Tropical PacificCentral Tropical PacificWestern/Central Tropical PacificWestern Tropical PacificTropical North Atlantic
Tropical South Atlantic
Tropical Atlantic Dipole
Indian Ocean Basin-WideWestern Tropical Indian Ocean
Southeastern Tropical Indian
Ocean
Indian Ocean Dipole-4-Coordinates
90°W – 80°W, 10°S – 0°150°W – 90°W, 5°S – 5°N
170°W – 120°W, 5°S – 5°N
160°E – 150°W, 5°S – 5°N
130°E – 150°W, 0°– 15°N
55°W – 15°W, 5°N – 25°N
30°W – 10°E, 20°S – 0°
TNA – TSA
40°E – 100°E, 20°S – 20°N
50°E – 70°E, 10°S – 10°N
90°E – 110°E, 10°S – 0°
WTIO – SETIO