1. Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology MeteoSwiss LM Physics Overview and Outlook 28 th EWGLAM and 13 th SRNWP Meeting Zurich, 9-12 October 2006 Marco Arpagaus

2. 2 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Outline Radiation Grid-scale clouds and precipitation / cloud microphysics Convection Turbulence Lower boundary condition soil-vegetation processes lakes

3. 3 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Radiation Scheme: δ-two stream radiation scheme after Ritter and Geleyn (1992) for short- and long-wave fluxes; full cloud- radiation feedback. Recent Extensions: Quasi-3d: Inclusion of 3d orographic effects on radiation (shadowing, slope angle, slope aspect, sky view). Upscaling: Use of coarser horizontal mesh to run the 1d radiation scheme in favour of running the scheme more often (aim: use 2*2 grid-points and reduce update frequency from hourly to every 15 min).

4. 4 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Radiation: Quasi-3d and upscaling Average solar surface radiation budget since forecast start (4 April 2005 00 UTC + 8 hrs) difference plot: version with topographic corrections minus version without topographic corrections original LM grid (2.8 km mesh-size) coarser (2x2) grid W/m 2

5. 5 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Grid-scale clouds and precipitation Operational schemes: Cloud-ice scheme: 5-class (vapour, cloud-water, cloud- ice, rain, and snow) single-moment scheme. Graupel scheme: 6-class (vapour, cloud-water, cloud-ice, rain, snow, and graupel) single-moment scheme for convection-resolving scales. Additional schemes: Seifert-Beheng (2006): 6 class two-moment scheme Reisner-Thompson (2004): 6 class single-moment scheme

6. 6 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch  g  0.9 g/cm 3 N 0 = 4*10 4 m -4 radar  g  0.2 g/cm 3 N 0 = 4*10 6 m -4 Grid-scale clouds and precipitation: Graupel scheme Problem: underestimation of precipitation amounts for convection-resolving LM. Cure: Use hail instead of graupel (as suggested by studies of idealised strong convection)?  No! LM (2.8 km mesh-size), 7 August 2004

7. 7 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Grid-scale clouds and precipitation: Prognostic precipitation LM – radar; north-westerly flow only (7 km mesh-size) 2004 2005 Problem: Orographic luv/lee pattern of precipitation. (Partial) solution: full prognostic treatment of precipitating hydrometeors (e.g., rain, snow, and graupel).

8. 8 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Convection: For 7 km mesh-size or larger … Operational: Tiedtke mass-flux scheme (1989); closure based on moisture convergence. Options: Tiedtke scheme with CAPE closure. Kain-Fritsch mass-flux scheme (1993) by Kain. Recently tested: Kain-Fritsch mass-flux scheme by Bechtold (2001), with closure based on CAPE. Results: Improved diurnal cycle (over flat terrain). Spin-up problem. (Stronger) overestimation of precipitation amounts, especially for light precipitation.  Code no longer maintained (???). – Test of IFS scheme instead?

9. 9 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Convection: For convection-resolving scales … No parameterisation scheme for (deep) convection. This however generates a serious problem: Boundary layer too moist. Low cloud cover too high.  Insufficient transport of moisture through top of the boundary layer! Quick solution: Use of Tiedtke scheme for shallow convection only. Envisaged long-term solution: Unification of turbulence and shallow convection scheme.  UTCS project.

10. 10 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Turbulence 2 nd -order one-equation closure scheme: prognostic TKE, algebraic relations for other 2 nd -order moments. Included are: subgrid-scale condensation and evaporation (moist conservative variables); effect of subgrid-scale horizontal inhomogeneity of the underlying surface (additional source of TKE, most notably in the stably stratified PBL). Surface-layer transfer scheme with a laminar-turbulent roughness sub-layer. Extensions:  UTCS project.

11. 11 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Lower boundary condition: Known surface types in LM sea / sea ice: externally prescribed surface temperature; constant during integration land: soil temperature and water content predicted by soil and vegetation model TERRA rock or ice: impermeable for water; temperature profile simulated by TERRA lake: prognostic surface temperature (water or ice) forecasted by lake model Flake A grid box is covered completely by either

12. 12 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Multi-layer soil and vegetation model Modification for thermal part: solution of heat conduction equation instead of extended force restore method  arbitrary number (and thickness) of soil layers  freezing/melting of soil water included (improved T2m in Winter)  simpler lower boundary condition Interception Snow no water flux prescribed T Two-layer TERRA (old) 1.0 m 0.1 m Snow constant T free drainage * * * * Multi-layer TERRA (new) * * Interception 2.43 m 7.29 m 0.01 m 0.81 m

13. 13 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Multi-layer soil and vegetation model Further modifications: thermal part: simplified treatment of melting snow time-dependent snow density (  [50, 400] kg/m 3 ; to reduce negative T2m bias over snow) dependence of snow albedo on time and forest cover (  [0.7, 0.2]; to reduce negative T2m bias over snow) hydrological part: new lower boundary condition (no water flux  gravitational drainage) Problems: soil dries out (especially lower layers)

14. 14 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Multi-layer soil and vegetation model More problems … thermal part: Numerical instabilities due to low heat capacity of thin uppermost layer (  limitation of temperature increment for uppermost soil layer) Interaction with snow analysis in case of analysed snow on soil with temperature above freezing (  reduction of temperature to zero degrees for uppermost layer and linearly reduced T increments for lower layers with temperatures above freezing) hydrological part: Interception store switched off due to instability problems (interaction with thin uppermost layer).

15. 15 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch New: Lake Model ‚FLake‘ (D. Mironov et al., see http://nwpi.krc.karelia.ru/flake) A computationally-efficient lake parameterisation scheme based on the idea of self-similarity (assumed shape, similar to the mixed-layer idea) of the evolving temperature profile. Prognostic variables are … the surface temperature, the mean temperature of the water column, the bottom temperature, the mixed-layer depth, the depth within bottom sediments penetrated by the thermal wave, and the temperature at that depth (bottom sediment module may be switched off). … plus in case of ice-covered lake the ice thickness, the temperature at the ice upper surface, the snow thickness, and the temperature at the snow upper surface (in the present pre-operational configuration, snow is treated in a simplified way).

16. 16 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch New: Lake Model ‚FLake‘ Single column test: Kossenblatter See, June 1998 FLake observations ice thickness LM test suite: Lake Balaton, 2006 test operational (SST analysis) lake surface temperature FLake is able to simulate diurnal as well as seasonal variations of lake surface temperature (T of water surface or of ice surface) realistically!

17. 17 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Lower boundary condition: New developments Urban model development within the FUMAPEX project Mosaic & tile approach is currently being implemented Measurement derived soil moisture analysis based on a standalone version of TERRA driven by observations

18. 18 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch COSMO Priority Projects UTCS: Towards a Unified Turbulence Shallow Convection Parameterisation  talk by Dmitrii Mironov QPF: Tackle deficiencies in Quantitative Precipitation Forecasts

19. 19 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch Quantitative Precipitation Forecasts Aim: Study LM (7 km mesh-size) deficiencies concerning QPF by running sensitivity experiments on a series of well chosen cases with poor model performance.  Results expected by September 2007. 18 March 2005

20. 20 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch To conclude … More information: Scientific documentation available on COSMO web-site at http://www.cosmo-model.org/public/documentation.htm. http://www.cosmo-model.org/public/documentation.htm Acknowledgements: All COSMO members, especially colleagues of Working Group 3 ‘Physical Aspects’. Thank you for your attention!

21. 21 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch

22. 22 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch References Radiation: B. Ritter and J.F. Geleyn, 1992: ‘A comprehensive radiation scheme for numerical weather prediction models with potential applications in climate simulations’, Monthly Weather Review, 120, 303-325. Grid-scale clouds and precipitation: LM Scientific Documentation A. Seifert and K.D. Beheng, 2006: 'A two-moment cloud microphysics parameterization for mixed-phase clouds. Part I: Model description.', Meteorology and Atmospheric Physics, 92, 45-66. G. Thompson, R.M. Rasmussen and K. Manning, 2004: 'Explicit Forecasts of Winter Precipiation Using an Improved Bulk Microphysics Scheme. Part I: Description and Sensitivity Analysis.' Monthly Weather Review, 132, 519-542.

23. 23 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch References Convection: M. Tiedtke, 1989: ' A comprehensive mass flux scheme for cumulus parameterization in large–scale models', Monthly Weather Review, 117, 1779-1799. J.S. Kain and J.M. Fritsch, 1993: 'Convective Parameterization for Mesoscale Models: The Kain-Fritsch Scheme'. In: The Representation of Cumulus Convection In Numerical Models. Meteorological Monographs No. 46, American Meteorological Society, 165-170. P. Bechtold, E. Bazile, F. Guichard, P. Mascart, and E. Richard, 2001: 'A mass-flux convections scheme for regional and global models', Quarterly Journal of the Royal Meteorological Society, 127, 869-886.

24. 24 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch References Turbulence: LM Scientific Documentation Surface: LM Scientific Documentation http://nwpi.krc.karelia.ru/flake

25. 25 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch TERRA: Snow density I Motivation: Soil module TERRA predicts too low T2m, when the surface is covered by snow over a longer period Reason: TERRA assumes a constant, rather low snow density  snow layer decouples soil and surface  radiative cooling at the top of snow layer is not compensated by soil heat flux T2m Terra – T2m OBS 4 March 2005, 6UTC, Germany frequency 2.0 0.0 -2.0 -4.0 -6.0 -8.0 constant snow density fresh snowold snow (identical water equivalent) (adopted from DWD, B. Ritter)

26. 26 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch TERRA: Snow density II Solution: Snow density depending on the age of snow Impact: Reduced T2m bias T2m Terra – T2m OBS 4 March 2005, 6UTC, Germany frequency 2.0 0.0 -2.0 -4.0 -6.0 -8.0 variable snow density (adopted from DWD, B. Ritter) (DWD, J.-P. Schulz)

27. 27 LM Physics | Overview and Outlook Marco Arpagaus (marco.arpagaus@meteoswiss.ch), Consortium for Small-Scale Modelling (COSMO)marco.arpagaus@meteoswiss.ch TERRA: Albedo of snow covered forest Motivation: Flat surface, like bare soil or low vegetation, can be covered completely by snow, whereas some parts of a forest will always remain snow free. This has a considerable impact on albedo Solution: Assuming an albedo of 20% for snow covered forest areas (instead of an albedo of 70% for other snow covered surfaces) Result: Reduction of negative T2m bias, in particular over Scandinavia