1. Forecast system version

Identifier code: ACCESS-S2

First operational forecast run: 20 October 2021

2. Configuration of the forecast model

Is the model coupled to an ocean model?   Yes: Atmosphere, land, ocean and sea-ice.

Coupling frequency: Hourly

The coupled model is described in Hudson et al (2017) and Wedd et al (2022).

2.1 Atmosphere and land surface

Model

Global Atmosphere 6.0 (GA6): The Unified Model version 8.6 (UM; Williams et al. 2015; Walters et al. 2017). 

Global Land 6.0 (GL6): Joint UK Land Environment Simulator (JULES; Best et al. 2011; Walters et al. 2017)

Horizontal resolution and gridN216 (~60km in the mid-latitudes)
Atmosphere vertical resolution85 levels
Top of atmosphere
Soil levelsFour soil levels
Time step

Detailed documentation:

2.2 Ocean and cryosphere

Ocean modelNEMO v3.4 (Madec et al. 2023; Megann et al. 2014)
Horizontal resolutionORCA 0.25
Vertical resolutionL75. Level thicknesses range from 1 m near the surface to ~200 m near the bottom (6000-m depth)
Time step
Sea ice modelCICE v3.1 (Hunke and Lipscomb 2010; Rae et al. 2015)
Sea ice model resolutionORCA 0.25
Sea ice model levels
Wave modelN/A
Wave model resolutionN/A

Detailed documentation: NEMO documentation, CICE documentation

3. Boundary conditions - climate forcings

Greenhouse gases
Ozone
Tropospheric aerosols
Volcanic aerosols
Solar forcing

Detailed documentation:

4. Initialization and initial condition (IC) perturbations

4.1 Atmosphere and land


HindcastForecast
Atmosphere initialization
ERA-Interim ( Dee et al. 2011) or the Bureau’s 4D-Var analysis (Bureau of Meteorology 2019a)
Atmosphere IC perturbationsHudson et al 2017

Land Initialization



Land IC perturbations

Soil moisture initialization

Snow initialization

Unperturbed control forecast?

Data assimilation method for control analysis: 

Horizontal and vertical resolution of perturbations:  

Perturbations in +/- pairs: 

Detailed documentation:

4.2 Ocean and cryosphere


HindcastForecast
Ocean initialization

Ocean IC perturbations

Unperturbed control forecast?

Detailed documentation:

 

5. Model Uncertainties perturbations:

Model dynamics perturbations
Model physics perturbations

If there is a control forecast, is it perturbed?


Detailed documentation: 

6. Forecast system and hindcasts

Forecast frequency
Forecast ensemble size
Hindcast years
Hindcast ensemble size
On-the-fly or static hindcast set?
Calibration (bias correction) period

7. Other relevant information


8. Where to find more information