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Progress in Anelastic Branch: Testing EULAG Model for Alpine Flows

Study on using EULAG model for Alpine flow simulations with simplified physics, comparing results with COSMO model, involving summer convection case study of Alpine region in July 2006.

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Progress in Anelastic Branch: Testing EULAG Model for Alpine Flows

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  1. Recent progress in the anelastic branch Bogdan Rosa1, Marcin Kurowski1, Damian Wójcik1, and Michał Ziemiański1 Acknowledgements: Oliver Fuhrer2,Zbigniew Piotrowski1,3 1. Institute of Meteorology and Water Management 2. Meteo Swiss 3. National Center for Atmospheric Research COSMO General Meeting, Rome, 5-9 September 2011

  2. Outline • Testing of the EULAG dynamical core for realistic flows over the Alpine topography with simplified physics parameterization • Coupling of EULAG dynamical core with COSMO via an interface • Technical testing of the coupled model by idealized cases COSMO General Meeting, Rome, 5-9 September 2011

  3. Testing the EULAG core for Alpine flows - a convection case study Task 1.3: Tests of the EULAG dynamical core for realistic flows over the Alpine topography with simplified physics parameterization To simulate realistic flows over the Alpine topography, with resolution ranging from 2.2, 1.1 km to 0.55 km, applying simplified parameterizations of basic subgrid processes. Compare results between EULAG and COSMO simulations. Moist processes are only simulated on explicit grid (i.e. no shallow convectionparameterization, no moist turbulence) with a simple microphysics (Kessler-scheme) in both models. Turbulent diffusion with a one-equation (TKE)-model (not necessarily the same in both models) without interactive parameterization, but using the surface and radiation fluxes from independent COSMO 2.2 km model runs (or simplified surface fluxes) COSMO General Meeting, Rome, 5-9 September 2011

  4. Description of the experiments Experiments involve case study of summer Alpine convection on 12 July 2006. Simplified parameterizations: • Boundary layer processes are represented by TKE (turbulent kinetic energy) model. • Surface fluxes and drag taken from the operation run of COSMO2 model for Switzerland. • Simple representation of moist processes (warm rain Kessler-scheme) Experiment setup: • Horizontal resolution 1.1 km, vertical resolution as in COSMO2 • The computational domain is restricted to 234x198 km and covers the Southern Alps • Initial, boundary conditions from COSMO2 operational run COSMO General Meeting, Rome, 5-9 September 2011

  5. General meteorological situation in the Alpine region - 12 July 2006 Synoptic situation in the area: slow-moving cold front in a shallow surface trough of low pressure This is representative case study for summer (convective) situations. MSG (Meteosat Second Genertion) 12:00 UTC Synoptic map – 2:00 UTC, 12 July 2006 COSMO General Meeting, Rome, 5-9 September 2011

  6. Diurnal cycle of potential temperature at the ground. Results from COSMO and EULAG experiments. COSMO General Meeting, Rome, 5-9 September 2011

  7. Time evolution of cloud water and stream lines from EULAG simulation. 14:00 UTC 12:00 UTC 18:00 UTC 16:00 UTC COSMO General Meeting, Rome, 5-9 September 2011

  8. Comparison of the EULAG simulation with satellite images 12:00 UTC 12:00 UTC 15:00 UTC 15:00 UTC Temporal and spatial structure of the simulated convection in the EULAG experiment closely resembles the actual development COSMO General Meeting, Rome, 5-9 September 2011

  9. Realization of the CDC plan – coupling CDC Project Plan Task 1.6: Coupling of EULAG dynamical core with COSMO via an interface. To better compare the behavior of the new dynamical core in more realistic model applications with full physics parameterizations, the dynamical core of EULAG will be coupled with the COSMO-model. As an intermediate step and to keep the amount of work in a reasonable range this will be done via an interface. This means that the EULAG dyn. core keeps his own variables, data structure, etc. It is not the aim to have a very efficient code version at this stage but to have a useable model version. COSMO General Meeting, Rome, 5-9 September 2011

  10. EULAG in Fortran 90 Migration of F77 EULAG code into F90 • Dynamic memory allocation (ALLOCATE/DEALLOCATE), no COMMON blocks, no DATA and BLOCKDATA statements • Modularization (data and source code separation, logical code decomposition into specialized modules) • Fortran 90 language syntax (free format syntax, upper/lower cases, names and comments in English, COSMO-like code indentations, new operators (>, <, etc.), KIND argument for real and integer types, no GOTO instructions,...) COSMO General Meeting, Rome, 5-9 September 2011

  11. C&E coupling – plugging the new dynamical core in A new configuration of EULAG dyn. core is done via namelists. EULAG dynamical core is temporarily plugged instead of default R-K dynamical core in src_runge_kutta module. It uses a set of variables defined in data_eufields module. In src_runge_kutta: Sections 1-3a: unchanged (initial time step, boundary tendencies, slow tendencies fromradiation, convection, Rayleigh damping, etc.) Sections 4a-6:unchanged (advection and diffusion of scalars, saturation adjustment) begin of a time step COSMO fields to EULAG Sections 3b-3c R-K time integration EULAG time integration EULAG fields to COSMO end of a time step COSMO General Meeting, Rome, 5-9 September 2011

  12. C&E coupling – parallelization MPI communication is basically organized in COSMO (init_procgrid). A new subroutine (emulate_geomset) is used to initialize EULAG's MPI variables following COSMO structure. This ensures identical domain decomposition in both models, i.e. the same grid points lie on the same processor domain. Single processor neighborhood Domain decomposition in EULAG COSMO General Meeting, Rome, 5-9 September 2011

  13. C&E coupling – grid adaptation COSMO staggered C-grid and EULAG unstaggered A-grid There are at least two options for distribution of vertical levels: 1) interpolation from COSMO to EULAG levels 2) 1:1 transformation for mass levels with interpolation of the velocities only (operational?) (1) EULAG (2) COSMO dz/2 domain height dz dz dz dz/2 nlevels n+1levels n+2levels COSMO General Meeting, Rome, 5-9 September 2011

  14. C&E coupling – data flow Mutual data transfer between COSMO and EULAG When data flow is required? 1. at the initialization stage (to initialize EULAG dynamical core) 2. at each time step C-grid (uC,vC,wC,T,p,forcings) A-grid(uE,vE,wE,Th, forcings)(uC,vC,wC,T) Sections 1-3a. COSMO fields to EULAG EULAG integr. R-K integr. EULAG fields to COSMO Sections 4a-6. COSMO General Meeting, Rome, 5-9 September 2011

  15. Realization of the CDC plan – testing C&E Task 1.7: Technical testing with COSMO by idealised cases The correct coupling of the EULAG dynamical core into COSMO can be at first tested with the implemented idealized test cases. This testing can be performed ‘by a press of a button’ in COSMO. The staff is now well trained with the idealized tests (see task 1.1), therefore it is not necessary to perform an extended analysis of such idealized tests, but simply to check if any technical coupling problems occur. Performed tests: 1. inertia-gravity wave (Skamarock and Klemp, 1994) 2. cold density current (Straka et al., 1993) COSMO General Meeting, Rome, 5-9 September 2011

  16. Two dimensional time dependent simulation of inertia-gravity waves Skamarock W. C. and Klemp J. B. Efficiency and accuracy of Klemp-Wilhelmson time-splitting technique. Mon. Wea. Rev.122:2623-2630, 1994 Initial potential temperature perturbation Initial potential temperature perturbation outlet inlet km Setup overview: • domain size 300x10km • resolution 1x1km,0.5x0.5km, 0.25x0.25km • rigid free-slip b.c. • periodic lateral boundaries • constant horizontal flow 20m/s at inlet • no subgrid mixing • hydrostatic balance • stable stratificationN=0.01 s-1 • max. temperature perturbation 0.01K • Coriolis force included km Constant ambient flow within channel 300 km and 6000 km long Initial velocity COSMO General Meeting, Rome, 5-9 September 2011

  17. Results - gravity waves in a short channel C&E Eulag C&E Eulag C&E Eulag COSMO General Meeting, Rome, 5-9 September 2011

  18. Comparison with analytical solution Eulag C&E Analytical COSMO General Meeting, Rome, 5-9 September 2011

  19. Profiles of potential temperature along 5000m height C&E Analytical COSMO General Meeting, Rome, 5-9 September 2011

  20. Gravity waves in a long channel Eulag C&E Eulag C&E Eulag C&E COSMO General Meeting, Rome, 5-9 September 2011

  21. Gravity waves in a long channel C&E Analytical C&E Analytical C&E Analytical COSMO General Meeting, Rome, 5-9 September 2011

  22. Profiles of potential temperature along 5000m height C&E Analytical COSMO General Meeting, Rome, 5-9 September 2011

  23. Two dimensional time dependent simulation of cold blob descending to the ground Straka, J. M., Wilhelmson, Robert B., Wicker, Louis J., Anderson, John R., Droegemeier,Kelvin K., Numerical solutions of a non-linear density current: A benchmark solution and comparisonInternational Journal for Numerical Methods in Fluids, (17), 1993 Experiment configuration: • isentropic atmosphere, θ(z)=const (300K) • periodic lateral boundaries • free-slip bottom b.c. • constant subgrid mixing, K=75m2/s • domain size 51.2km x 6.4km • bubble min. temperature -15K • bubble size 8kmx4km • no initial flow • integration time 15min open b.c. r periodic b.c. periodic b.c. free-slip b.c. COSMO General Meeting, Rome, 5-9 September 2011

  24. Distribution of potential temperature after 900 sec C&E inviscid 100m C&E viscous – diffusive forcing from COSMO parameterizations 100m COSMO General Meeting, Rome, 5-9 September 2011

  25. Comparison of the potential temperature distribution Cosmo 100m C&E Eulag COSMO General Meeting, Rome, 5-9 September 2011

  26. Comparison of the horizontal and vertical velocities obtained from three different models Cosmo Cosmo 100m 100m C&E C&E Eulag Eulag COSMO General Meeting, Rome, 5-9 September 2011

  27. Comparison of potential temperature distribution at resolution 25 m Cosmo 25m C&E Eulag COSMO General Meeting, Rome, 5-9 September 2011

  28. Comparison of the horizontal and vertical velocities obtained from three different models Cosmo Cosmo 25m 25m C&E C&E Eulag Eulag COSMO General Meeting, Rome, 5-9 September 2011

  29. CONCLUSIONS 1. MOTIVATION • Temporal and spatial structure of the simulated convection in the EULAG experiment closely resembles the actual development. • EULAG code has been successfully implemented in COSMO. • Results of the idealized tests obtained using the hybrid E&C model are in goodqualitative and quantitative agreement both with reference and analytical solutions. • Small differences indicate the need for further testing and verification of the E&C code. • Dynamical core of the developed prototype, cooperates correctly with the diffusive forcing from COSMOparameterizations. COSMO General Meeting, Rome, 5-9 September 2011

  30. Realization of the CDC plan – documentation of the already performed tasks. B. Rosa, M. J. Kurowski, and M. Z. Ziemiański, 2011, Testing the anelasticnonhydrostatic model EULAG as aprospective dynamical core of a numericalweather prediction model. Part I: Dry Benchmarks, Acta Geophysica, 59 (6),DOI: 10.2478/s11600-011-0041-1. M. J. Kurowski, B. Rosa and M. Z. Ziemiański, 2011, Testing the anelasticnonhydrostatic model EULAG as a prospective dynamical core of numerical weather prediction model. Part II: Simulations of a supercell, ActaGeophysica, 59 (6), DOI: 10.2478/s11600-011-0051-z. M. Z. Ziemiański, M. J. Kurowski, Z. P. Piotrowski, B. Rosa and O. Fuhrer, 2011, Toward very high resolution NWP over Alps: Influence of the increasing model resolution on the flow pattern, Acta Geophysica, 59 (6), DOI: 10.2478/s11600-011-0054-9 COSMO General Meeting, Rome, 5-9 September 2011

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