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HOME > Ensemble Model Prediction > Model Outlines

Outline of the operational Ensemble Prediction Systems for one-month and seasonal prediction

JMA routinely operates Ensemble Prediction Systems (EPSs) to support from medium-range to seasonal prediction. In JMA, the Global Ensemble Prediction System (Global EPS; GEPS) is operated to support for issuing typhoon information as well as one-week, two-week and one-month forecasts, while the Seasonal Ensemble Prediction System (Seasonal EPS) is operated to support issuing three-month and warm/cold season forecasts as well as El Nino monitoring and outlook.

The numerical prediction model used in the Global EPS is an atmospheric general circulation model (AGCM) that is a low-resolution version of the Global Spectral Model (JMA-GSM) used for global deterministic numerical weather prediction. The numerical prediction model used in the Seasonal EPS is a coupled ocean-atmosphere general circulation model (CGCM), which consists of the AGCM (a low-resolution version of the GSM) and the ocean general circulation model (OGCM).

The specifications of the Global EPS for one-month prediction and the Seasonal EPS are shown in the following table.

Specifications of EPSs for one-month and seasonal prediction

Global EPS for one-month prediction Seasonal EPS (JMA/MRI-CPS2)
Last upgrade March 2021 June 2015
Model Atmospheric general circulation model (AGCM) with 2 Tiered SST approach Coupled ocean-atmosphere general circulation model (JMA/MRI-CGCM2)
Atmospheric general circulation model
Horizontal resolution:
   TL479 (approx. 40 km)(up to 18 days),
   TL319 (approx. 55 km)(after 18 days)
Vertical levels: 128 levels up to 0.01 hPa
Horizontal resolution: TL159 (approx. 110 km)
Vertical levels: 60 levels up to 0.1 hPa
Oceanic general circulation model
Horizontal resolution: 1.0º longitude, 0.3-0.5º latitude
Vertical levels: 52 levels and a bottom boundary layer
Integration range 34 days 7 months
Initial conditions Atmospheric: JMA Global Analysis
Oceanic: None
Land: JMA land surface analysis
Atmospheric: JRA-55(Japanese 55-year Reanalysis)
Oceanic: Ocean data assimilation(MOVE/MRI.COM-G2)
Land: JRA-55 land analysis
Boundary conditions Sea Surface Temperature (SST): Prescribed SSTs using persisted anomaly with daily climatological SST up to 11day forecast. After that, in tropics and sub-tropics, SST is relaxed to the ensemble-mean SST operationally predicted by JMA's coupled Seasonal EPS
Sea ice: Prescribed sea ice concentration using persisted anomaly with daily climatological sea ice concentration
SST: One-tier method
Sea ice: Interactive sea ice model
GHG concentration Constant RCP4.5
Orography GTOPO30 dataset (30″ × 30″) spectrally truncated and smoothed
Ensemble Perturbation method Combination of
   Singular vectors (SVs) and Local Ensemble Transform Kalman Filter (LETKF),
   stochastic physics scheme,
   SST perturbations and
   Lagged Average Forecast (LAF)
Combination of
   Breeding of Growing Modes (BGM),
   stochastic physics scheme and
   Lagged Average Forecast (LAF)
Ensemble size 50 51
Freq. of model product creation Once a week
(Model operation)
Once a month (around 20th of every month)
(Model operation)
Hindcast period Jan 1981 - Dec 2020 Jan 1979 - Dec 2019
Hindcast ensemble size 13 / initial date
Initial dates: 15th and the end of calendar month
10 / month
For further information on Global EPS, Seasonal EPS and Specifications of JMA-GSM, please refer to Numerical Weather Prediction of JMA.

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