1. GloSea4 – the new Met Office Hadley Centre seasonal forecast system
Adam Scaife and Alberto Arribas
January 2009
© Crown copyright Met Office

2. GloSea3 vs GloSea4 GloSea3 GloSea4 HadCM3 (N48L19 – 1/3L40) HadGEM3
Model
HadCM3
(N48L19 – 1/3L40)
HadGEM3
(N96L38-ORCA1L42)
Initialization
Atmos/soil: reconf. of ECMWF 4D-Var
Ocean: UM 3D-OI
Atmos/soil/sea-ice: reconf. of Met Office 4D-Var
Ocean: NEMO 3D-OI
IC uncertainties
Wind stress and SST perturbations added to a central analysis
Weekly lagged approach
Model uncertainties
None
RP + SKEB2
Forecast ensemble
41-members (monthly bursts from 1st )
30 members (weekly bursts)
Hindcast ensemble
Run a priori off-line
15-members / 15-years ( ) ERA-40
Run real-time with forecast
10-members / 15-years ( ) ERA-interim
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3. GloSea4 : System design/infrastructure
Monday
ADA(NWP) + ODA
Weekly IC
N forecasts (6-month)
Archiving/post-processing
Tue - Sun
ADA(NWP) + ODA
N forecasts (6-month)
Archiving/post-processing
FCST
Every week
Pull together last 4-weeks fcsts/hcst
Post-processing
Products / web display
Every day
‘Weekly’ ICs
N forecasts (6-month): Y-years, M-members
Archiving/post-processing
Off line
Continuous ODA (e.g – 1998)
‘Weekly’ Atmos + land.surf. Reanalysis data
HCST
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4. Issues with ICs perturbations
Pert. Members
CTRL
(Bowler, Arribas and Mylne, MWR)
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5. Issues with ICs perturbations
Lagged approach
GloSea4 to follow a lagged initialization approach
Flow dependent perturbations
Representing true uncertainty (spatial and magnitude)
Current
system
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6. Future upgrade for coupled initialisation and stratosphere
April 2009
Future upgrade
System configuration
Fcst: 30 members
Hcst: 15-yr (most recent years from ERA-Interim); 10 members
Hcst: 20-yr; 10 members
[cost incr.: x 1.3]
Model configuration and resolution
HadGEM3 N96L38+ORCA1L42
HadGEM3 N96L85+ORCA1L42
[cost incr.: x 1.6 (with same timestep)]
Initialization
Atmosphere: reconfiguration of NWP / ERA
Ocean: DA: improved covariances
Sea-ice: Include assimilation
Coupled initialization as described in Anderson et al. (2008).
Replacement of NEMO-OI by NEMOVAR
Representation of uncertainties
ICs: lagged approach
Model:RP + SKEB2
Improvement of SKEB2
Post-processing
- GloSea3 calibration and display system
- Complete MO-EPS Integrated web display system
- Improvement of new calibration methods
- Improvement of integrated display system
Computing cost
~1.5%
~3%
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