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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 Niño 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 (based on 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-CPS3)
Last upgrade March 2023 February 2022
Model Atmospheric general circulation model (AGCM) with 2 Tiered SST approach Coupled ocean-atmosphere general circulation model (JMA/MRI-CGCM3)
Atmospheric general circulation model
Horizontal resolution:
   TQ479 (approx. 27 km)(up to 18 days),
   TQ319 (approx. 40 km)(after 18 days)
Vertical levels: 128 levels up to 0.01 hPa
JMA-GSM with wide-ranging updates for CPS3
Horizontal resolution: TL319 (approx. 55 km)
Vertical levels: 100 levels up to 0.01 hPa
Oceanic general circulation model
Horizontal resolution: 0.25º x 0.25º
Vertical levels: 60 levels
Integration range 34 days up to 7 months
Initial conditions Atmosphere: JMA Global Analysis
Ocean: N/A
Land: JMA land surface analysis
Atmosphere: JMA Global Analysis
Ocean: MOVE/MRI.COM-G3 (Low-res. 4DVAR + High-res. downscaling)
Sea ice: MOVE/MRI.COM-G3 (3DVAR)
Land: Offline model runs (forced by JRA-3Q and JMA Global Analysis)
Boundary conditions Sea Surface Temperature (SST): Prescribed SSTs using persisted anomaly with daily climatological SST up to 6-day forecast. After that, 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
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 1991 - Dec 2020 Jan 1991 - Dec 2020
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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