Status of ALADIN/ALARO p hysics

1. Current developments: Neva Pristov Near future plans and further developments: Jean-Francois Geleyn Status of ALADIN/ALARO physics

2. ALARO-0 physics package - introduction • continuity + improvements • economical computation • algorithmic flexibility  good basis for further developments • numerical challenges

3. Current developments • Radiation • Orographic forcing • Large scale precipitation • Prognostic turbulent scheme • Precipitating convection J-F Geleyn, G. Hello, N. Pristov, Y. Bouteloup, M. Derkova, J. Masek, A.Trojakova, R. Fournier B. Carty, F. Bouyssel, R. Brožkova, J-F Geleyn, M. Derkova, R. Mladek, J. Cedilnik, D. Drvar, I. Beau B. Carty, J-F Geleyn, J. Cedilnik, M. Tudor, D. Drvar F. Vana, J. Cedilnik, M. Tudor, J-F Geleyn Luc Gerard, J-M Piriou, I. Stiperski, D. Banciu, J-F Geleyn

4. Orographic forcing • modifications in gravity wave parameterization • implemented already in ALADIN, operational at CHMI Features: • more consistent definition of wave- and form drag- components • a lift acting (ortogonal) to the geostrophic wind • replacing of the envelope orography by a mean orography • mountain sub-grid effects are considered also down to scales of around 5 km

5. Radiation Aim: • using the current delta-two stream approximation of radiative transfer equation for solar and thermal bands • economical computation (a good quality cost ratio) • better consideration of clouds New features: • new technique for thermal radiative fluxes computation on the basis of Net Exchanged Rate (NER) formalism • gaseous transmition functions for computation of optical depth closer to RRTM scheme • introduction of the complete aerosol model • updating of the cloud optical properties

6. CTS EWS EBL Comparison of fluxes in the thermal radiation Radiation • Computation of optical depths using the gazeous RRTM transmission functions

7. Radiation – cloud optical properties problem: • saturation effect on cloud properties depends also on properties and geometry of cloud layers above and below aim: • to parameterize the saturation effect taking into account cloud overlaping option profit from prognostic cloud water and ice

8. Radiation – cloud optical properties Validation method • create idealized cloud simulation model to get reference values • comparision for transmissivities and reflectivities • for a homogeneous single cloud • for the impact of non-homogeneity (3 layers) • for the impact of non-uniformity (3 layers, still simple exercise)

9. Radiation – cloud optical properties Current scheme solar band thermal band transmissivities homogeneous clouds reflectivities

10. Radiation – cloud optical properties New scheme solar band thermal band transmissivities homogeneous clouds reflectivities

11. Radiation – cloud optical properties New scheme solar band thermal band transmissivities non-homogeneuos clouds reflectivities

12. Radiation – cloud optical properties New scheme solar band thermal band transmissivities non-uniformity clouds reflectivities

13. Large scale precipitation Aim: • using the benefit of the good tuning of current scheme • better space distribution of precipitation (less upslope, more downslope precipitaton) Features: • a simple micro-physics scheme with 5 water phases included into precipitation scheme cloud water, cloud ice, liquid, solid precipitation - new prognostic variables water vapour all phase-changes go through the vapour phase only rain and snow leave the particle of the air all non-precipitating species have the same vertical velocity

14. Large scale precipitation pseudo fluxes: • condensation/evaporation (transfer between vapour and liquid water) • auto conversion (transfer between liquid and rain water) • evaporation of precipitation (transfer between rain and vapour water) • freezing/sublimation (transfer between vapour water and ice) • auto conversion (transfer between ice and snow) • sublimation of the falling snow (transfer between snow and vapour water) treatment of rain and snow: • link between flux and mean fall-speed (new) • collection (4 cases) • evaporation • melting/freezing • sedimentation of precipitation (new)

15. Prognostic turbulent scheme Aim: • to extend the current vertical diffusion scheme to be compatible with the general and more physical (AROME) TKE scheme. • using the benefit of the current vertical diffusion scheme (known properties, tuning and stability issues) Requirements: • modularity - allowing gradual conversion to a full TKE scheme • time stability - combination of the two implicit schemes (dissipation and self-transport), anti-fibrillation treatment Features: • the turbulent memory of the previous timesteps is kept • the advection and diffusion of TKE is added to the current scheme • more general computation of mixing length (planed)

16. Precipitating convection aim: • convection at grey zone • combining relevant and subgrid contribution to cloud condensation and precipitation basis: the version of the scheme developed by Luc Gerard,including the MT (microphysics and transport) idea of Jean-Marcel Piriou and enhanced by the current interfacing and modularising work of Ivana Stipersky => Acronym: 3MT (Modular Multi-scale Microphysics and Transport)

17. Precipitating convection Luc Gerald • the convection is extincting gradually with the resolution increase • convection does not produce precipitation itself; the updraught detrains cloud condensates, which are put into micro-physics scheme together with resolved condensed part • prognostic convective closure Jean-Marcel Piriou • proposed method can in principle handle dry, non-precipitating or precipitating convection. • the convective tendencies are expressed directly in terms of micropysics and transport, based on the concept of Buoyant Convective Condensation (BCC) rate • the closure assumption can shift continuously from a CAPE behaviour to a humidity convergence behaviour

18. Precipitating convection ALARO: • adapt to micro-physics scheme and thermodynamics • diagnostic/historic/prognostic closure • compatibility with the vertical diffusion • treatment of the diagnostic coudiness

19. Future evolutions and perspectives • Short term actions • - further optimise mountain drag-lift scheme • - search the best option of the pseudo-TKE numerics • - tuning of auto-conversion • More ambitious actions - capitalise on the transversal aspects of 3MT - optimise the ‘grey-zone’ use - intermittent use of the NER-based radiation - unified cloud definition and use - non-precipitating convection use of 3MT

20. Capitalising on the transversal aspects of 3MT • Open topics (with only a preliminary answer in the ALARO-0 solution): • Rate of convective entrainment; • Computation of up- & downdrafts vertical velocities; • Convective closure assumption; • Prognostic, historic or diagnostic aspect of the 3 previous items; • Pseudo-adiabatic type computations for convective ascending and subsiding motions; • ‘Dynamical’ characteristics of those ascending and subsiding motions; • Source term for convective ‘friction’; • Microphysical terms (except sedimentation).

21. Optimising the ‘grey-zone’ use (upon a good start) • Situation of 10 Septembre 2005 (results obtained par Luc Gerard); • Urban flooding in Brussels in the afternoon; • The ‘oper’ ALADIN-Belgique did not forecast much rainfall; • Forecasting from the 12 UTC network for the period 18-19 UTC; • Results compared to radar accumulations for one hour (max ~70 mm); same colour scale.

22. The simulation converges realistically when resolution increases. There is hardly any sign of a ‘grey zone’ syndrome. x=2.2 km x=4.0 km x=7.0 km x=9.9 km The first prototype is encouraging (1/3)

23. CV on off 9.9 km CV on off 2.2 km Convection auto-extinguishs itself at increased resolution, and furthermore ... The first prototype is encouraging (2/3)

24. Convective precipitations Stratiform precipitations 2.2 km CV LS LS seul Total Max. precip. 32 33 50 64 0 … even at the meso- scale, at the heart of convective cells, there is still as much parameterised precipitations as resolved ones (and the tool giving this result seems reliable for this problem). The first prototype is encouraging (3/3)

25. Intermittent use of the NER-based radiation To ‘import / reframe’ Exists ! Fluxes of the time- step Done (ALADIN2) ACRANEB-8 2nd part Model of opt Clouds + Aerosols In progress Modified proposal (extreme case with 8 fields to store) Complete comput. in clear sky Complete comput. in clear sky N t Flux  LW & SW etc. ‘Interpolation’ opt, ,  gaz (8 x) For the ALARO case ; else, who wants … t modèle

26. Unified cloud definition and use • In ALARO-0, the cloudiness used for radiation and moist vertical diffusion will still be ‘diagnostic’ and the ‘prognostic’ one of LG’s scheme (coming from both condensation computations) will input only microphysics. • In the future, the latter will also be passed to the next time step and used for all purposes, after experimentation and tuning have shown this is safe for all possible weather types.

27. Non-precipitating convection use of 3MT • In the M-T proposal of J-M Piriou’s thesis one central paradigm is reversed: rather than impliciting the microphysics (stationary cloud) and expliciting the detrainment (closure), one does the opposite. • This is achieved by separating microphysics and transport terms. • But this idea can in principle be extended to non-precipitating (and even dry) convection with seamless transitions (next 3 dias). • A huge unifying potential to explore as soon as feasible!

28. Modélisation 2: Equations convectives: proposition MT-CCB Perspective historique des équations convectives à échelle résolue Bilan nuageux stationnarisé Yanai (1973): Détraînement à échelle résolue Pseudo-subsidence Bougeault (1985): Pseudo-subsidence, détraînement uniforme et soustr. turbulence (Q1c: réchauffement convectif, Q2c: assèchement convectif fois L) Transport Condensation nette GATE (1974), Arakawa-Schubert (1974), Bougeault (1985), Tiedtke (1989), Fritsch-Chappell (1980), Kain-Fritsch (1990), KF-Bechtold (2001), …

29. Modélisation 2: Equations convectives: proposition MT-CCB Equations convectives à échelle résolue: proposition MT-CCB Condensation Convective Brute Evaporation des gouttes nuageuses Evaporation des gouttes de pluie Chal. sens. précip. Transport MT-CCB: MT-CCB M & T couplés: (Q1c: réchauffement convectif, Q2c: assèchement convectif fois L) Dans l’approche MT-CCB plus besoin de paramétriser le détraînement à échelle résolue. Réalisme du schéma reporté sur celui de sa microphysique. Transport Condensation nette

30. Modélisation 2: Equations convectives: proposition MT-CCB Equations convectives à échelle résolue: proposition MT-CCB CVP CVNP CV sèche MT-CCB: Continuité de la microphys. Microphys. Vit. vert., ferm. Simpl. de la microphys. Complexif. de la microphys. Air humide, CVPYanai (1973) Bougeault (1985) CRM, LES Synergie méthodologique

31. Conclusions • We cannot yet prove anything but we are rather confident to reach the short term objectives of the action (continuity, innovation and numerical safety/efficiency). • If this is indeed the case, there will be a huge potential of joint development (around a few hopefully acceptable basic choices). In the end, further success will depend on the attractivity of this concept.