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HOME > Ensemble Model Prediction > Description of JMA's Global Ensemble Prediction System for one-month prediction

Description of JMA's Global Ensemble Prediction System for one-month prediction

Outline

JMA's Global Ensemble Prediction System (Global EPS; GEPS) is an integrated system to support for issuing typhoon information, one-week forecasts and one-month forecasts by JMA. 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. Atmospheric and land initial conditions obtained from the JMA Global Analysis and its land surface analysis. The sea surface temperature (SST) is used as the lower boundary condition for the AGCM and prescribed using persisted anomaly with daily climatological SST. The sea ice is also used as the lower boundary condition and prescribed using the persisted anomaly with daily climatological sea ice concentration. Initial perturbations are generated using the combination of Singular vectors (SVs) and Local Ensemble Transform Kalman Filter (LETKF). A stochastic physics scheme is used in consideration of model uncertainties associated with physical parameterizations. The Sea Surface Temperature (SST) perturbation is used as surface boundary perturbations. In addition, the Lagged Averaged Forecast (LAF) method is adopted to produce products for one-month prediction.

Real-time operation

The Global EPS for one-month prediction provides 50 members once a week, which are composed of 13 members each integrated from initial fields at 00 UTC and 12 UTC every Tuesday and Wednesday. The overall 50-member ensemble is then used for a one-month forecast issued every Thursday. Products for one-month prediction including prediction maps and gridded datasets are made available on the TCC website every Thursday.

Performance of Global EPS for one-month prediction

A set of hindcasts (re-forecasts) was carried out in the similar way as the real-time operation with some modifications. The verification results based on the hindcasts are given from a hindcast verification page. A set of the hindcast data is provided on request from a page for gridded data download (registered users only).

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