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1. Forecast system version

System name: GloSea5-GC2

First operational forecast run: 3 February 2015

2. Configuration of the forecast model

Is it a coupled model?  Yes: Atmosphere, land, ocean and sea-ice.

Coupling frequency: 3-hourly coupling between atmosphere-land and ocean--sea-ice.

The coupled model Global Coupled 2 (GC2) is described in Williams et al, 2015.

2.1 Atmosphere and land surface


Met Office Unified Model (UM) - Global Atmosphere 6.0

Joint UK Land Environment Simulator (JULES) - Global Land 6.0

Horizontal resolution and gridN216: 0.83 degrees x 0.56 degrees (approx 60km in mid-latitudes)
Atmosphere vertical resolution85 levels
Top of atmosphere85km
Soil levels


Level 1 : 0 - 0.1 m

Level 2 : 0.1 - 0.35

Level 3 : 0.35 - 1.0 m

Level 4 : 1.0 - 3.0 m

Time step15 minutes

Detailed documentation:

JULES documentation

Global Atmosphere 6.0 & Global Land 6.0: Walters et al, 2017

2.2 Ocean and cryosphere

Ocean model

NEMO v3.4 - Global Ocean 5.0

Horizontal resolutionORCA 0.25
Vertical resolutionL75
Time step22.5 minutes
Sea ice modelCICE v4.1 - Global Sea-Ice 6.0
Sea ice model resolutionORCA 0.25
Sea ice model levels5 categories + open water
Wave modelN/A
Wave model resolutionN/A

Detailed documentation: NEMO documentation, CICE documentation

Global Ocean 5.0: Megann et al, 2014

Global Sea Ice 6.0: Rae et al, 2015.

3. Initialization and initial condition (IC) perturbations

3.1 Atmosphere and land

Atmosphere initialization
ERA-InterimMet Office Global Hybrid 4D-VAR
Atmosphere IC perturbationsNoneNone

Land Initialization

Climatology/ERA-InterimClimatology/Met Office Global Hybrid 4D-VAR
Land IC perturbationsNoneNone
Soil moisture initializationClimatologyClimatology
Snow initializationERA-InterimMet Office Global 4D-VAR
Unperturbed control forecast?NoNo

Detailed documentation:

Met Office Global Hybrid 4D-VAR: Clayton et al, 2013

3.2 Ocean and cryosphere

Ocean initializationGloSea Ocean Sea-Ice Analysis (GS-OSIA)Forecast Ocean Assimilation Model (FOAM)
Ocean IC perturbationsNoNo
Unperturbed control forecast?NoNo

Detailed documentation:

The GS-OSIA and the FOAM system both use the Nucleus for European Modelling of the Ocean data assimilation system (NEMOVAR). This is a 3d-VAR data assimilation scheme. The GS-OSIA uses different surface forcing (ERA-interim) and observation sets as it is a historical analysis. FOAM uses surface forcing from the Met Office Global NWP model and real-time observations.

The common NEMOVAR system is described in Blockley et al, 2014. Details of the GS-OSIA can be found in MacLachlan et al, 2015.

4. Model uncertainties perturbations:

Model dynamics perturbationsNone
Model physics perturbationsAtmosphere stochastic physics scheme, SKEB2

If there is a control forecast, is it perturbed?

No control

Detailed documentation:

SKEB2: Bowler et al, 2009

5. Forecast system and hindcasts

Forecast frequencydaily
Forecast ensemble size2 per day
Hindcast years23 (1993-2015)
Hindcast ensemble size7 per start date
Hindcast start dates1, 9, 17, 25 of each month
On-the-fly or static hindcast set?on-the-fly

6. Where to find more information

GloSea5 system:

Model description references:

Initialisation references:

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