Common HIRLAM and ALADIN-M/F physics plan (08/05) J-F Geleyn, B. Hansen-Sass, G. Hello & L. Rontu Oslo mini-workshop Mesoscale physics and diagnostic tools 12/12/2005

Basic guidelines I) We all want to develop physics towards the finer scales with a need to increase the realism of the parameterised phenomena. II) It is understood that each contributing group is also in a continuous process of improving its physics package. Each group will be responsible for maintaining the physics in a state working safely within the IFS coding framework. III) We would like to also make progress towards a common coding framework. This implies some concrete coordination efforts over the years to come. IV) In order to be able to develop the physics schemes with regard to physical realism, numerical stability, accuracy and economy it is essential to develop common tools for different types of validation. n V) Clean inter-comparisons of different schemes, e.g. using common tools and rules, are a prerequisite for common conclusions.

Split of planned actions n From longer term to short term: –Basic scientific issues; –Algorithmic issues; –Interfacing and diagnostic issues; –Transversal challenges. n Concrete tasks only for n This mini-workshop as kick-off meeting

Basic scientific issues (1/2) n Selected themes: –Representation of small cumulus clouds (non- precipitating convection) Central topic; (too?) many ideas. –Convection for the scales where it still needs to be parameterised ‘Grey zone’ definition; work on entrainment rate. –Turbulent scheme Attention on stable cases; march towards 3rd order. –Increased realism, tuning and improvement of the microphysics Validation methods; how to avoid proliferation? n Organisational aspects: scientific mini- workshops (Tartu is a super example).

Basic scientific issues (2/2) n Special theme: –Link with the surface externalisation Joint topic with another community, currrent partial lack of visibility, intrinsic complexity of the issue => A careful scientific watch for 2006.

Algorithmic issues n Selected themes: –Radiation Better strategy for intermittent types of computation. –Better algorithmic of the microphysical computations (towards time steps > 60s) Interplay with convection; modularity. –Turbulence (Study of staggering, fibrillation and implicitness issues for prognostic TKE schemes) Trying to sort out the ‘CBR vs. CBR’ problem. –Turbulence (3D minus 1D aspects) Immediate need: to simply document the issue. n Organisational aspects: prepare convergence via some anticipating work

Interfacing and diagnostic issues n Selected themes: –Choices for the non-hydrostatic aspects of the interfacing –Stabilisation of the link between DDH and interfacing equations Anchor point for the development of an ambitious common diagnostic strategy. –Realisation of the main interfacing routines Starting ‘backwards’ in order to disconnect as long as possible from previous item; link with SURFEX = calendar constraint. n Organisational aspects: permanent WG needed (the work is ongoing but scattered)

Transversal challenges (1/2) The development of common tools appears very important. It might turn out that the degree of collaboration success depends on how well such developments can be handled in the future. n Selected themes: –Development of common validation tools well- adapted to test several physical options in the same dynamical core: 1D model; ALAPIA-type model; One (at least) 3D benchmark case.

Transversal challenges (2/2) n Selected themes (continued): –Long term aspects of the interfacing and portability rules Rules D & E of the ‘Winter 04/05 PDI document’. –Consistency of the Méso-NH and AROME/ALARO/HIRLAM development constraints Item of growing importance needing first a better definition.

Conclusion Let us all go back from here with a clear view of our common actions for The ensuing progress and redefinition tasks will follow naturally.