1. Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology MeteoSwiss High resolution COSMO runs for dispersion applications in complex terrain MeteoSwiss – C2SM COSMO User Workshop 22 October 2009 Balázs Szintai MeteoSwiss Advisors: Pirmin Kaufmann, Mathias Rotach, Oliver Fuhrer

2. 2 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Outline Introduction Objectives of the work LITFASS-2003 campaign Sensitivity to horizontal diffusion TKE budget terms TRANSALP-89 campaign Introduction of a new coupling approach Validations of tracer concentrations Summary and Outlook

3. 3 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Introduction Air quality modelling systems Numerical Weather Prediction (NWP) model Air quality model 3D atmospheric fields (u,v,w,T,q) Transport and diffusion of pollutants Coupling

4. 4 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Objectives of the work Improve the turbulence coupling between NWP and dispersion models Validate turbulence characteristics from the COSMO model To use: turbulence measurement campaign (LITFASS-2003) Validate simulated concentrations To use: tracer experiment (TRANSALP)

5. 5 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) LITFASS-2003 Measurement campaign conducted in the area of Lindenberg Main goal: measurement of turbulent fluxes in an inhomogeneous terrain Case study: 2003-05-30 : convective day, calm winds, no clouds Simulation of the whole diurnal cycle Measurements used: Radiosoundings Micrometeorological stations  all land cover types Tower turbulence measurements (at 50 and 90 m) 20 km

6. 6 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Large Eddy Simulation Large Eddy Simulation runs were performed at the Environmental Fluid Mechanics Laboratory (EFLUM) at EPFL by Daniel Nadeau LES details: Solves the filtered incompressible N-S equations Lagrangian scale-dependent dynamic subgrid scale model Spectral representation in the horizontal directions Finite differences in the vertical direction Periodic lateral boundary conditions Domain size 6 x 6 km horizontal (Δx = Δy = 94 m) 3 km vertical (Δz = 47 m) Time step: 0.2 s 3 hours of simulation from 9 to 12 UTC Geostrophic forcing calculated from COSMO-7 analysis (constant in time, vertically changing) Changing lower BC from measurements for each land cover type Work in progress, preliminary results

7. 7 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) COSMO at 1 km COSMO-7 COSMO-1

8. 8 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Horizontal resolution: 0.0089° ~ 1 km Runge-Kutta time integration scheme Timestep : 10 s Operational external parameters (soil type) are not accurate in the area  improved dataset from Felix Ament is used Soil analysis was produced with a one-month TERRA standalone run forced with COSMO-7 analyses Investigated: Horizontal diffusion (numerical and physical) TKE budget terms Implicit TKE diffusion Finer vertical resolution COSMO runs

9. 9 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Horizontal diffusion Without horiz. diff. itype_turb=3 hd_corr_in=0.0 With horiz. diff. itype_turb=3 hd_corr_in=0.75 3D turbulence itype_turb=3 l3dturb=.true.

10. 10 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Component testing Budget terms: I. : Local tendency II. : Buoyancy production term III. : Shear production term IV. : Turbulent transport of TKE and pressure correlation term V. : Dissipation Task 2 in the UTCS Project Prognostic equation for TKE: I. II. III. IV. V.

11. 11 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) TKE budget - measurements Average values computed from two sonic anemometers at 50 and 90 m Turbulent transport: triple correlations (M. Mauder, Research Centre Karlsruhe) Dissipation: turbulence spectrum (D. Michel, University Basel) Positive values of turbulent transport in COSMO Large negative imbalance in measurements Transport Dissipation Budget imbalance Buoyancy Shear TKE

12. 12 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) TRANSALP-89 LPDM 1989 October: Tracer experiments in Southern Switzerland Meteorological conditions: Anticyclone, cloud free, low winds Development of valley wind system Tracer release: between 10 and 11 UTC Numerical setting: ERA-Interim COSMO-7 COSMO-2

13. 13 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Motivation Implement and test a new turbulence coupling approach suited for steep and narrow Alpine valleys Weigel et al., 2007: turbulence variables over the valley floor scale well during convective conditions, if surface fluxes from the sunlit slope are used MeasuredModelled Weigel et al., 2007

14. 14 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Validation of wind With original IFS soil moisture the the COSMO simulation is too moist  late onset of valley wind Soil moisture in COSMO was reduced by 50% Magadino Piotta Riviera Leventina Blenio 10 km DD FF

15. 15 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Validation of tracer concentrations Tracer portioning between Leventina and Blenio is not accurate Highest values by the „direct” approach, lowest values by the new approach

16. 16 High resolution COSMO runs for dispersion applications in complex terrain Balázs Szintai (balazs.szintai@meteoswiss.ch) Summary LITFASS: Some kind of horizontal diffusion is needed at 1 km TKE is simulated quite accurately, although this is not the case for all the budget terms TRANSALP: A new scaling approach by Weigel et al. suited for Alpine valleys was implemented in the coupling interface between COSMO and LPDM The new approach results in stronger turbulence, thus lower and (in some cases) more accurate concentrations in the valley COSMO-1 simulation does not improve the results significantly  higher resolution externals needed?

17. Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology MeteoSwiss Thank you for your attention!