The Met Office aqua-planet runs using pre-HadGAM1 Rachel Stratton & Chris Dearden © Crown copyright

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. © Crown copyright

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 © Crown copyright

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 http://www.met-office.gov.uk/research/hadleycentre/pubs/HCTN/index.html © Crown copyright

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 © Crown copyright

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 © Crown copyright

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. 10 -40 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. © Crown copyright

Any Questions ? © Crown copyright