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WG2- report SMC-meeting 01/02 Feb. 2017, Geneva Michael Baldauf (DWD)

This report discusses the implementation of higher order discretization schemes in the COSMO model, resulting in improved efficiency and reduced bias in summer precipitation. The dissertation by J. Ogaja is also mentioned.

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WG2- report SMC-meeting 01/02 Feb. 2017, Geneva Michael Baldauf (DWD)

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  1. WG2- report SMC-meeting 01/02 Feb. 2017, Geneva Michael Baldauf (DWD) M. Baldauf (DWD)

  2. Higher order discretization A. Will, J. Ogaja (BTU Cottbus) • Status • Large improvement in efficiencydone! In thecomparison advS4-P4 / advUP5-P2:advection ~10%, fast waves ~3% more expensive.withoutartificialdiffusion, thecostsareroughlythe same! • Dissertation J. Ogajaisavailable. • Model crash COSMO-DE at ‚20.06.2013‘ hasbeensolved • Summerlyprecipitation dry biasismuchreduced in theconvection-permittingsetup! M. Baldauf (DWD)

  3. Higher Order Spatial Schemes for the COSMO Model A. Will, J. Ogaja (BTU Cottbus) , New discretization of the advection operator: AdvS4 := kinetic energy conserving discretization (Morinishi et al. (1998) ) Additionally one can use 4th order discretizations of horizontal derivatives in the fast waves solver. , :

  4. Morinishi et al. (1998) - spatial discretisation A. Will, J. Ogaja (Univ. Cottbus) main results: • power spectrum of kinetic energy (here: annual (for 1979) and meridional mean for 3-6 km layer) almost no reduction by the newscheme at small wavelengths! • climate runs over several years stable without artificial horizontal diffusion! Linear stability analysis of this new discretization does not show drawbacks! ( talk M. Baldauf in WG2 meeting) (from Ogaja, Will, MetZ) M. Baldauf (DWD)

  5. 4. Real case climate simulation: Stability ,

  6. Next steps: • Transfer the code from version 5.0 to 5.5 ( M. Baldauf)(not before March 2017) • Run this new version on NUMEX ( M. Baldauf) • Deliver documentation (COSMO Sci. Doc. part I, possibly alsoa COSMO-TR (?)) ( A. Will) • expected availability for the official code version: ~June 2017 M. Baldauf (DWD)

  7. New Bott advection scheme W. Schneider, A. Bott (Univ. Bonn) • Status: • NUMEX-Exp. at DWD from ‚21.05.-30.06.2016‘ just hasbeenfinished. • (at 28. Jan.) •  Verificationis still needed. • Plan: • Ifverificationissuccessfulthen bring intoofficialcodeversion. • Mightbe a possible alternative forthe COSMO-D2 project at DWD • Documentation (Sci. Doc. part I: M. Baldaufor W. Schneider) M. Baldauf (DWD)

  8. PP CDIC – Status report Comparisonofthedynamicalcoresof ICON and COSMO SMC-meeting 01/02 Feb. 2017, Geneva Michael Baldauf (DWD) M. Baldauf (DWD)

  9. Aimof CDIC Deliver an asobjectiveaspossiblecomparisonofthedynamicalcores of COSMO and ICON withtheemphasis on limited areamodellingby • Task 1: idealisedtests (mainfocus) • Task 2: semi-realistictests • Task 3: performance on different platforms • Task 4: Principalproperties • Task 5: Suitabilityforotherapplications (climate/chemistry) Project Team (currently) Michael Baldauf (DWD) Amalia Iriza (NMA) Rodica Dumitrache (NMA) Guy deMorsier (MeteoCH) Damian Wojcik (IMGW) Marina Shatunova (Roshydromet) Denis Blinov (Roshydromet) M. Baldauf (DWD)

  10. Task 1. Good performance on a standard set of idealized test cases 1. Advection test with nonlinear dynamics (Schär et al. (2002)) NN ?! 2. Atmosphere at rest (Zängl et. al (2004) MetZ) Barbu/Dumitrache/Iriza  3. Cold bubble (Straka et al. (1993)) (unstationary density flow) Barbu/Dumitrache/Iriza  4. Mountain flow tests (stationary, orographic flows) 4.1 Schaer et al. (2002), section 5b Baldauf  4.2 Bonaventura (2000) JCP “ ! 4.3 3D-case (dry) Schmidli (?) “ ! 5. Linear Gravity waves (Baldauf, Brdar (2013)) Baldauf  6. Warm bubble (Robert (1993), Giraldo (2008)) Wojcik ! 7. Moist, warm bubble: Weisman, Klemp (1982) MWR Wojcik  8. Advection tests for tracer schemes (solid body rotation, …) Will (without FTE) ! Overall assessment: • volunteersforalmost all testshavebeenfound • testcasesare a bitbehindschedule togetfamiliarwith ICON ismoredifficultcomparedto COSMO mainly due totheunstructuredgrid (bothcodecomplexityanduseofexternalgridfiles) M. Baldauf (DWD)

  11. Task 1. Good performance on a standard set of idealized test cases Test case 2: atmosphere at rest (R. Dumitrache, A. Iriza) global model ICON with dx ~80 km, mountains at equator. w after 12h for 15 or 30 vertical levels (equidistant) and with or without Smagorinski-diffusion M. Baldauf (DWD)

  12. reference solution: Test case: falling cold bubble Status: approximately correct, but should work better! Reasons? M. Baldauf (DWD)

  13. Test case 4.1: Linear flow over mountains COSMO ICON dx=250m colors and black dotted lines: COSMO or ICON blue lines: analytic solution M. Baldauf (DWD)

  14. Test case 5: linear wave expansion Initialization similar to Skamarock, Klemp (1994) Small scale test with a basic flow U0=20 m/s, f=0 Black lines: analytic solution (Baldauf, Brdar (2013) QJRMS) Shaded: COSMO M. Baldauf (DWD)

  15. Convergence behaviour COSMO ICON T‘ w M. Baldauf (DWD)

  16. Task 2: Ability to handle semi-realistic cases reasonably well Test casesaredefined: • strong advectivecase: storm ‚Elon‘, 9-10 Jan. 2015 (MeteoCH) • Bora event: 6-8 Feb. 2012 (possibly also 19 Feb. 2016) (RHM) However, the ICON developersdidn‘twanttodistributethe ‚limited areamode‘ versionbeforethe ICON trainingscourse 28.02.-03.03.17 becausedocumentation will not bereadybeforethisevent.  heavy delay in thistask M. Baldauf (DWD)

  17. Task 3. Scalability/Performance suitable for operations as well as for future supercomputing platforms Nothing done yet Task 4: Identification of differences in dynamical core formulations stability analysis of both dynamical cores has been done Task 5. Suitability of ICON dynamical core for other applications than NWP (climate, chemistry, ...) compared to the COSMO model Until now only one volunteer to assess ICON-ART (Roshydromet). Volunteer(s) from CLM community are welcome, too! M. Baldauf (DWD)

  18. PP CELO COSMO-EULAG operationalisation SMC-meeting 01/02 Feb. 2017, Geneva Project leader: Bogdan Rosa (IMGW) M. Baldauf (DWD)

  19. Due tothedevelopments at ECMWF (PantaRhei-project: developmentof a • dynamicalcoreforthecompressible, non-hydrostatic Euler equations • based on the EULAG numercalframeworkas a prototype for a FV-IFS (projectleader: P. Smolarkiewicz) ) • thefocusoftheprojectchangedtowardsthisgoal. • Status: • Standard setofidealizedtestsnowhasbeenperformedand • presentedat the COSMO-GM 2016 andWG2/CELO/CDIC-meeting. • Cold density current (Straka et al., 1993) • • Linear gravity waves (Skamarock et al., 1994) • • Dry orographic flows (Klemp et al. (1977), Bonaventura (2000)) • • Moist orographic flows (Kurowski et al., 2013) M. Baldauf (DWD)

  20. Next steps • Further tuning and optimization • Development of a single precision version and restart capabilities • Implementation of full ICON physics Next larger goal: transfer the EULAG part into the official COSMO code. B. Rosa: “The problem with the pressure perturbation (close to the ground) in the current prototype version of COSMO-EULAG has not been solved yet. The code is under testing and a number of issues/places have to be examined. Further idealized tests (Baldauf, Brdar, 2013) will be done.  will not be ready to bring the EULAG code into official version of COSMO 5.6. However, the perspective for bringing EULAG to next COSMO version (5.7) seems to be quite realistic.” M. Baldauf (DWD)

  21. Proposal for a new priority project ('CEL-ACCEL' or ‚CELO-2‘ or …) SMC-meeting 01/02 Feb. 2017, Geneva Project leader: Zbigniew Piotrowski (IMGW) M. Baldauf (DWD)

  22. Project goals: • Further stepstooperationalize COSMO-EULAG (bothanelasticandcompressibleversion). In detail: • Prepare COSMO-EULAG ortheuse on modern accelerators (GPUs, manycore CPUs) withtheaidof Domain SpecificLanguages (STELLA, GridTools) andopenACC • Adaptation of EnKF capabilities (KENDA, KENDA-O) to the EULAGnumerical formulation • Optimization of numerical and physical formulation of COSMO-EULAG at and near the surface IMGW has successfully applied for external funding (3 full positions) by the 'European Regional Development Fund' to bring CELO to a pre-operational level for this project. M. Baldauf (DWD)

  23. Proposed tasks Task 1: Adaptation of COSMO framework to embrace 0-m level of EULAG DC realization of turbulent fluxe at the surface; ICON physics adaptation(remember the A-grid formulation of EULAG) 2.4 FTE  WG 3a Task 2: Accelerator port of COSMO-EULAG Use GridTools for the rewrite of the COSMO-EULAG dyn. core openACC for physics components 1.8 FTE  WG 6 Task 3: Enhance the efficiency of COSMO-EULAG algorithms in particular the iterative solver (multgrid preconditioning, adaptive time step) 0.4 FTE  WG 2 M. Baldauf (DWD)

  24. Task 4: Data assimilation capability of COSMO-EULAG • use of different prognostic variables a problem? • 0.6 FTE  WG 1 • Task 5: Testing of COSMO-EULAG on accelerators • Stability and performance evaluation on several supercomputer architectures • 0.8 FTE  WG 6 • planned duration: 03.2017 – 09.2019 • planned ressources: 6.25 FTE • Links to other projects • ESCAPE (H2020) (led by ECMWF): development of energy efficient algorithms • PantaRhei (at ECMWF) develops the compressible EULAG dyn core for the purpose of a Finite volume IFS prototype M. Baldauf (DWD)

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