EPS operation for long-range forecasting

JMA's long-range forecasting model is a coupled ocean-atmosphere general circulation model (CGCM) type with atmospheric and oceanic initial conditions obtained from the JMA Climate Data Assimilation System (JCDAS) and MOVE/MRI.COM-G, respectively. Land surface climatological conditions are used as the initial conditions for the CGCM, and a land surface model coupled to the AGCM is used for the prediction of land surface conditions. The climatological distribution of sea ice is used as the lower boundary condition.


The EPS for long-range forecasting is run every five days with nine members. Initial perturbations are estimated for both the atmosphere and the ocean, and atmospheric initial perturbations are obtained using the Breeding of Growing Modes (BGM) method. Oceanic initial perturbations are estimated through MOVE/MRI.COM-G forced with the surface heat and momentum fluxes of the atmospheric initial perturbation fields.


The EPS with the CGCM for long-range forecasting, as well as for El Niño prediction, adopts a combination of the initial perturbation method and the Lagged Average Forecasting (LAF) method. Nine members are run every five days, and the EPS consists of 51 members for the latest six initial dates. The 51-member ensemble is used for the three-month forecast issued every month and for a warm/cold season forecast issued five times a year (in February, March, April, September and October). GPV products of the EPS for long-range forecasting are made available on the TCC website by the 22nd of each month.

Schema of aggregation for the ensemble members in t the EPS for long-range forecasting

updated : Feb.8, 2010

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