Bogdan Rosa 1, Marcin Kurowski 1, Damian Wójcik 1, and Michał Ziemiański 1 Acknowledgements: Oliver Fuhrer 2, Zbigniew Piotrowski 1,3 1. Institute of Meteorology and Water Management 2. Meteo Swiss 3. National Center for Atmospheric Research Recent progress in the anelastic branch COSMO General Meeting, Rome, 5-9 September 2011

Outline COSMO General Meeting, Rome, 5-9 September 2011 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

Testing the EULAG core for Alpine flows - a convection case study COSMO General Meeting, Rome, 5-9 September 2011 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 convection parameterization, 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 Description of the experiments Experiments involve case study of summer Alpine convection on 12 July 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

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

Diurnal cycle of potential temperature at the ground. Results from COSMO and EULAG experiments.

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

Comparison of the EULAG simulation with satellite images 12:00 UTC 15:00 UTC 12:00 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

Realization of the CDC plan – coupling COSMO General Meeting, Rome, 5-9 September 2011 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.

EULAG in Fortran 90 COSMO General Meeting, Rome, 5-9 September 2011 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,...)

C&E coupling – plugging the new dynamical core in COSMO General Meeting, Rome, 5-9 September 2011 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 from radiation, convection, Rayleigh damping, etc.) Sections 4a-6: unchanged (advection and diffusion of scalars, saturation adjustment) Sections 3b-3c R-K time integration EULAG time integration COSMO fields to EULAG begin of a time step end of a time step EULAG fields to COSMO

C&E coupling – parallelization COSMO General Meeting, Rome, 5-9 September 2011 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. Domain decomposition in EULAG Single processor neighborhood

C&E coupling – grid adaptation COSMO General Meeting, Rome, 5-9 September 2011 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?) COSMO (1)(2)EULAG dz dz/2 n levelsn+1 levelsn+2 levels domain height

C&E coupling – data flow COSMO General Meeting, Rome, 5-9 September 2011 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 R-K integr. EULAG integr. COSMO fields to EULAG EULAG fields to COSMO Sections 1-3a. Sections 4a-6. C-grid (u C,v C,w C,T, p, forcings) A-grid (u E,v E,w E,Th, forcings) (u C,v C,w C,T)

Realization of the CDC plan – testing C&E COSMO General Meeting, Rome, 5-9 September 2011 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)

Two dimensional time dependent simulation of inertia-gravity waves COSMO General Meeting, Rome, 5-9 September 2011 Skamarock W. C. and Klemp J. B. Efficiency and accuracy of Klemp-Wilhelmson time-splitting technique. Mon. Wea. Rev. 122: , 1994 Initial potential temperature perturbation Setup overview: domain size 300x10 km resolution 1x1km, 0.5x0.5 km, 0.25x0.25 km rigid free-slip b.c. periodic lateral boundaries constant horizontal flow 20m/s at inlet no subgrid mixing hydrostatic balance stable stratification N=0.01 s -1 max. temperature perturbation 0.01K Coriolis force included Constant ambient flow within channel 300 km and 6000 km long km outlet inlet Initial potential temperature perturbation Initial velocity

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

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

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

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

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

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

COSMO General Meeting, Rome, 5-9 September 2011 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 comparison International Journal for Numerical Methods in Fluids, (17), 1993 free-slip b.c. open b.c. periodic b.c. r Experiment configuration: isentropic atmosphere, θ(z)=const (300K) periodic lateral boundaries free-slip bottom b.c. constant subgrid mixing, K=75m 2 /s domain size 51.2km x 6.4km bubble min. temperature -15K bubble size 8km x 4km no initial flow integration time 15min

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

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

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

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

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

1. MOTIVATION CONCLUSIONS COSMO General Meeting, Rome, 5-9 September 2011 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 good qualitative 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 COSMO parameterizations.

Realization of the CDC plan – documentation of the already performed tasks. COSMO General Meeting, Rome, 5-9 September 2011 B. Rosa, M. J. Kurowski, and M. Z. Ziemiański, 2011, Testing the anelastic nonhydrostatic model EULAG as a prospective dynamical core of a numerical weather prediction model. Part I: Dry Benchmarks, Acta Geophysica, 59 (6), DOI: /s M. J. Kurowski, B. Rosa and M. Z. Ziemiański, 2011, Testing the anelastic nonhydrostatic model EULAG as a prospective dynamical core of numerical weather prediction model. Part II: Simulations of a supercell, Acta Geophysica, 59 (6), DOI: /s 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: /s