Physics developments in ALADIN: towards higher resolution

1. Physics developments in ALADIN:towards higher resolution Neva Pristov Environmental Agency of Slovenia Meteorological office 26th EWGLAM, Oslo

2. Content • Cloudiness • Orographic forcing • Radiation • Microphysics and convection T.Haiden, A. Kann, H. Seidl, R.Brožkova, ... B.Carty, F.Bouyssel, R.Brožkova, J-F Geleyn, M.Derkova, R.Mladek, J.Cedilnik, D.Drvar J-F Geleyn, G.Hello, N.Pristov, Y.Bouteloup, M.Derkova Luc Gerard 26th EWGLAM, Oslo

3. Cloudiness • Problem • Underestimating of low cloudiness • Structure of lifted inversions poorly predicted • Overestimated diurnal cycle of temperature • Method • Experiments (1-d and 3-d) with different cloudiness parameterizations • Study effects of vertical diffusion parameterization on inversion 26th EWGLAM, Oslo

4. Low cloudiness sensitivity experiment horizontal diffusion of temperature - on Seidl/Kann scheme Improved stratus forecast, but areal coverage still insufficient horizontal diffusion of temperature - off 26th EWGLAM, Oslo

5. Cloudiness Scheme modifications • modify the vertical profile of critical relative humidity - to get medium and high clouds starting to appear at lower relative humidity values. • tuning of the X-R function in Xu-Randall cloudiness scheme • use of the random/maximum overlap for clouds instead of the random overlap 26th EWGLAM, Oslo

6. Cloudiness Total cloudinessprevious new Amount of clouds is more realistically distributed 26th EWGLAM, Oslo

7. Orographic forcing • modification in orography drag parametrization • revised dependencies of the drag on the Froude number • a lift orthogonal to the geostrophic wind and not any more to the real wind • replacing envelope orography by a mean orography 26th EWGLAM, Oslo

8. Orographic forcing 10km 5km 2.5km 1.25km Experiments (Semi-Academical)on ALPIA domain Using new drag/lift scheme • The new scheme is tuned to be resolution independent • Parameterization is needed for horizontal mesh sizes from ~ 5 km • The envelope can be suppressed by the new lift scheme • The thin line between param / no param is not clear 26th EWGLAM, Oslo

9. Orographic forcing envelope disappearance and drag/lift improvement + more realistic flow around the mountain ranges + better wind scores at 850 hPa and around + less upwind exaggerated precipitations on mountain flanks (unfortunately) without any shift in position, + increased compatibility with the theory of sub-grid mountainous forcing, - too weak 10 m winds near mountains - decreased foehn effect that was apparently well tuned before, - slightly negative upper air geopotential scores 26th EWGLAM, Oslo

10. Orographic forcing Envelope orography, old drag scheme Difference Mean orography, new drag scheme Difference Total precipitation sum 62 days SOP MAP 1999 • Bias reduced by 25% • Maxima around moutains peaks decreased • No improvement in distribution Analyses 26th EWGLAM, Oslo

11. Radiation completely modifies the thermal computations 2 modes: • 'statistical' - 'basic' call at each time-step; • 'self-learning' - some chosen time steps are far more expensive to better tune the 'classical' ones used in-between 26th EWGLAM, Oslo

12. Radiation EWS EBL CTS CTS+EWS+EBL decomposition of the thermal radiative exchange terms in absence of scattering 26th EWGLAM, Oslo

13. Radiation Scores with respect to FMR (new ARPEGE) Geopotential Better on all domains 26th EWGLAM, Oslo

14. Radiation Scores with respect to FMR (new ARPEGE) Temperature Better for Europe and N20 (except at very top) Worse for Tropics and S20 26th EWGLAM, Oslo

15. Radiation • Computation of optical depths using the gazeous RRTM transmission functions CTS EWS EBL Comparison of fluxes – encouraging results 26th EWGLAM, Oslo

16. Combined effects of improvements Cloudiness, radiation, drag, without envelope Cloudiness, radiation, drag, without envelope+ SLHD A- 986 hPa B- 1000 hPa C- 1007 hPa Storm 14 September 2003 Black Sea MSL pressure 26th EWGLAM, Oslo

17. Microphysics and convection An integrated approach • Microphysics • 3 prognostic: vapour, cloud ice, cloud liquid water • 2 diagnostic: precipitation liquid and solid • Fluxes of water and heat • Parametrization of WBF and riming process • Convective updraught • detrains condensates (no precipitation) • Downdraught 26th EWGLAM, Oslo

18. Microphysics and convection Comparision of 2 experiments • Precipitating • Water condensing in the updraught is immediately precipitated to the ground • Integrated • Updraught detrains condensates 26th EWGLAM, Oslo

19. Microphysics and convection Squall line 14 August 1999 Western Belgium MSL pressure and precipitation ‘precipitating’ integrated 26th EWGLAM, Oslo

20. Microphysics and convection Precipitation continues to increase Produce less precipitation Maximum of precipitation on right place Smoother pressure field Squall line 14 August 1999 Western Belgium ‘precipitating’ integrated 26th EWGLAM, Oslo

21. More cloud ice Microphysics and convection Vertical cross section – cloud condensates and T ‘precipitating’ integrated 26th EWGLAM, Oslo

22. Microphysics and convection Extended updraught activity Higher velocities Vertical cross section – updraught vertical velocity ‘precipitating’ integrated 26th EWGLAM, Oslo

23. Microphysics and convection Problem • Not enough precipitation because of vertical distribution of condensates Solution • Detrainment connected with • Entrainment by the same cloud at lover level • Neighbourhood clouds 26th EWGLAM, Oslo

24. Additional effort is needed 26th EWGLAM, Oslo