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Detailed model description

Page containing details for all model configurations available in S2S since the project start => JMA model description

Overview of the model changes

Model version	Implement. date in S2S	Time range	Resolution	Ens. Size	Frequency	Re-forecasts	Rfc period	Rfc frequency	Rfc size	Ocean resolution	Active Sea Ice	Remarks
CPS3	19/02/2023	d 0-34	Tl319L100	4+1	daily	fixed	1991-2020 (model version date 30/09/2022)	2/month (*3)	4+1	0.25° L60	yes	6-hourly 10u/v added since 19 Feb 2023 the new reforecast set (model version date 30/09/2022) to be added soon
GEPS2203	15/03/2022	d 0-34	Tq479/Tq319L128	49+1	weekly (Wed) lagged eps created from 2 runs (*5)	fixed	1991-2020 (model version date 31/03/2022)	2/month (always on the 15th and the last day of month *3)	12+1	N/A	N/A
GEPS2103	30/03/2021	d 0-34	Tl479/Tl319L128	49+1	weekly (Wed) lagged eps created from 2 runs (*5)	fixed	1981-2020 (model version date 31/03/2021)	2/month (always on the 15th and the last day of month *3)	12+1	N/A	N/A
GEPS2003	24/03/2020	d 0-34	Tl479/Tl319L100	49+1	weekly (Wed) lagged eps created from 4 runs (*4)	fixed	1981-2010 (model version date 31/03/2020)	2/month (always on the 15th and the last day of month *3)	12+1	N/A	N/A
GEPS1701	22/03/2017	d 0-34	Tl479/Tl319L100	49+1	weekly *(Wed) lagged eps created from 4 runs (4)**	fixed	1981-2012 (model version date 31/01/2017)	3/month (always on the 10th, 20th and the last day of month *3)	4+1	N/A	N/A
GSM1403C	06/01/2015	d 0-34	Tl319/L60	24+1	2/week (Tue, Wed)	fixed	1981-2010 (model version date 04/03/2014)	3/month (always on the 10th, 20th and the last day of month *3)	4+1	N/A	N/A

(*3) For exact list of JMA reforecast dates for each model version date refer to https://apps.ecmwf.int/datasets/data/s2s-reforecasts-instantaneous-accum-rjtd/levtype=sfc/type=cf/

Description of the main changes

CPS3

General changes:
- model changed from GEPS to CPS coupled to an ocean model
- output frequency for 10 metre wind and precipitation changed from 24 hour to 6 hour
- increased number of vertical layers for vertical velocity
- Surface thermal radiation downwards parameter newly provided
Real-time forecasts changes:
- ensemble size decreased from 25 to 5
- frequency changed from twice a week (every Tuesday and Wednesday at 12Z) to every day (00Z)
- total data size increased from 6.6 GB to 8.4 GB per week, but decreased from 3.3 GB to 1.2 GB per day due to change the ensemble size and a forecast frequency
Re-forecasts changes:
- ensemble size decreased from 13 to 5
- total data size for the re-forecast: ~1TB
- frequency (twice a month) and period (1991-2020) don't change, but start dates for each re-forecast year changed to:
  Jan: 16 and 31
  Feb: 10 and 25
  Mar: 12 and 27
  Apr: 11 and 26
  May: 16 and 31
  Jun: 15 and 30
  Jul: 15 and 30
  Aug: 14 and 29
  Sep: 13 and 28
  Oct: 13 and 28
  Nov: 12 and 27
  Dec: 12 and 27

GEPS2203

The horizontal resolution improved to about 40km up to 18 days and about 55km after that. The physical parameterization schemes and two-tiread SST method are improved.
operational from 15 Mar 2022

GEPS2103

The new JMA real-time ensemble system includes 2 start dates (Tuesdays and Wednesdays at 12Z) instead of the previous 4 runs (see the description in GEPS1701 below). The ensemble size is 25 members for both days and the resulting new lagged ensemble for S2S is a single 50-member ensemble starting on Wednesdays at 12Z.
operational from 30 Mar 2021

GEPS2003

two-tiered Sea Surface Temperature (SST) method is implemented in addition to improved physical parameterization schemes in the forecast model. In this approach, the oceanic lower-boundary condition is relaxed from the anomaly-fixed SST to the ensemble-mean SST based on prediction using the Seasonal Ensemble Prediction System (Seasonal EPS).
There is no change in the number of fields for real-time data but the number of reforecast ensemble members is increased from 5 to 13, and the number of frequency is reduced from 3 to 2 per month.

operational from 24 Mar 2020

GEPS1701

The new JMA real-time ensemble system includes 4 start dates (Tuesdays at 00Z and 12Z + Wednesdays at 00Z + 12Z) instead of the previous 2 only (25-member ensembles starting on Tuesday 12Z and Wednesday 12 Z). The ensemble size is 13 members for Tuesdays 12Z and Wednesdays 00 and 12Z and 11 members for Tuesdays 00Z. Because the usage of such data would be very difficult for users, a lagged ensemble is being created for S2S archive instead. The resulting new lagged ensemble is a single 50-member ensemble starting on Wednesdays at 12Z

operational from 22 Mar 2017