1. The Met Office aqua-planet runs using pre-HadGAM1
Rachel Stratton & Chris Dearden
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2. Who is involved at the Met Office?
Main point of contact is the Climate Model Development and Evaluation group in the Hadley Centre
Chris Dearden
Gill Martin/Mark Ringer
Other groups with an interest are;
Convection in APP( atmospheric processes & parameterisation), Steve Derbyshire, Rachel Stratton , Anna Maidens.
NWP global model development and diagnostics, Martin Willetts and Sean Milton.
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3. The Met Office runs
The runs were done during 2003 well before HadGAM1 was finalised (~late 2004).
Model used will be referred to as pre-HadGAM1 (it is close but not identical to HadGAM1).
Resolution used N96L38 and N48L38
N96L38 (1.25ºx1.625º) was used for some of the non-symmetric SSTs
N48L38 (2.5ºx3.75º) was used for the symmetric cases
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4. HadGAM1 – description Dynamics & grid information
Non-hydrostatic model, lat long Arakawa C grid
Vertical coordinate – hybrid height, 38 levels, top ~40km, with Charney-Phillips staggering.
Semi-lagrangian advection, monotone treatment of tracers, Semi-implicit time integration
Dynamics physics coupling – parallel splitting of slow processes, sequential fast processes
Time step 30 minutes
Convection called 3 times per time step
See eg Hadley Centre tech note 54
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5. HadGAM1 description continued
Physics Parameterisations
Ewards-Slingo radiation, non-spherical ice crystals
Boundary layer – new scheme (Lock et al 2000)
Microphysics – mixed phase scheme with prognostic ice (Wilson & Ballard 1999)
Convection – revised mass flux scheme (see talk later)
Clouds – Smith scheme (1990), parameterised RH crit (Cusack et al 1999)
Gravity-wave drag – low level flow blocking (Webster et al 2003) only applies over orography.
Land surface and hydrology – MOSES-II
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6. Pre- HadgAM1 differences from HadGAM1
Pre-HadGAM1 does not include;
RHcrit parameterisation in the cloud scheme.
Final changes to the convective cloud amount.
Sharp tails in the Boundary layer scheme.
The latest parameterisation of non-spherical ice in the radiation scheme.
Changes to the absorption by water vapour.
Final cloud microphysics changes.
Aqua-planet run does not include the sulphur cycle
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7. Aims/Focus of Met Office APE work?
Use as a intermediate tool for developing new, or assessing existing, model parameterisation schemes.
E.g. for a new convection scheme start with single column model runs, then aqua-planet then full model.
All runs use control SST, N48L38 & very short e.g days.
Particular interest is in using to understand tropical performance
Martin Willetts – looked at time series focussing on convection increments in the tropics.
Intercomparison project - interest
In understanding mechanisms – convection, BL, surface, interaction with dynamics
Chris Dearden – plans to do further work for his MSC dissertation (he may rerun using HadGAM1), will concentrate on tropical performance.
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8. Any Questions ?
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