1. Implementation and validation of a prognostic large-scale cloud and precipitation scheme in ARPEGE precipitation scheme in ARPEGE (F.Bouyssel,Y.Bouteloup, P.Marquet) HIRLAM workshop on convection and clouds Tartu,Estonia, 24-26/01/2005

2. Outlook 1. Description of the scheme 2. Validation 3. Conclusions and perspectives

3. Description of the large-scale cloud and precipitation scheme

4. Generalities  Developed by P. Lopez (QJRMS, 2002)  Designed for variational assimilation of cloud and RR obs  Prognostic var : Qc (cloud condensates) & Qp (precip water)  Semi-lagrangian treatment of the fall of precipitation (Lopez,2002)

5.  Specification of hydrometeor distributions: Concentration : N(D) = N 0 exp(- D) (Marshall-Palmer) Mass: M(D)=  D  Fall velocity: V(D)=  D   Condensation/evaporation of cloud water: Smith (1990) Triangular PDF  Cloud water amount (Qc) and Cloud fraction (Neb)  Autoconversion: Kessler-type (1969)  Collection of cloud water by rain and snow: Integration of the collection eq. over N(D) and V(D)  Precipitation evaporation: Integration over N(D) of the equation:  Precipitation sedimentation: Originality: conservative semi-lagrangien treatment based on constant fall speeds for snow and rain (0.9 and 5 m/s)

6. Partition of Qc into Ql,Qi

7. Tuning of Rh crit

8. Sensitivity to fall speeds (Lopez,2002)

9. Sensitivity to main tunable parameters (Lopez,2002)

10. Validation

11. Diffusion on conservative variables (q t,  l )

12. Validation on 4 months integration (T149C1.0) Q liq Q ice Q neb Oper New

13. Validation on 4 months integration (T149C1.0) MEAN=8.53 W.m -2 RMS=25.4 W.m -2 MEAN=5.42 W.m -2 RMS=23.0 W.m -2 Oper New

14. Validation on 4 months integration (T149C1.0) MEAN=2.13 W.m -2 RMS=12.5 W.m -2 MEAN=0.72 W.m -2 RMS=11.8 W.m -2 Oper New

15. Validation on 4 months integration (T149C1.0)

16. Preliminary results in T358C2.4 (forecasts only)

17. Case study : 09/12/2004 Oper New

18. Case study : 09/12/2004 OperNew

19. ConclusionsPerspectives

20. Conclusions  Importance of diffusion on conservative variable  Stability and acceptable sensitivity to time step length  Promising results to improve mountain precipitations (intensity and localisation)  Improvment of LWP in the Tropics  Overestimation of cloud condensate and cloudiness near the ground

21. Perspectives  Modify snow melting  Evaluation in assimilation experiments  Take into account turbulence to diagnose Qc and Neb  Introduce further sophistications