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Recents Improvements in LMZ Code

Recents Improvements in LMZ Code. Lucio TORRISI CNMCA – Pratica di Mare (Rome) l.torrisi@meteoam.it. Introduction. A z-coordinate version of LM (LMZ) has been developed at DWD using the cut cell approach (Steppeler et al., 2002: MWR).

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Recents Improvements in LMZ Code

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  1. Recents Improvements in LMZ Code Lucio TORRISI CNMCA – Pratica di Mare (Rome) l.torrisi@meteoam.it Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  2. Introduction • A z-coordinate version of LM (LMZ) has been developed at DWD using the cut cell approach (Steppeler et al., 2002: MWR). • LMZ should provide more accurate precipitation and wind forecasts in mountainous regions than the terrain following coordinate version of LM (LMTF). • LMZ core needs to be intensively tested and evaluated, before other development effort is done. • A number of real forecast tests with LMZ/LMTF was performed (Steppeler and Torrisi, 2006: Adv. Num. Sem. presentation). An improvement in total precipitation forecast associated with small amount of convective precipitation was found for LMZ. Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  3. Overview • LM/LMZ configuration. • Problem: underestimation of convection • Problems in parallel machines • Case study: precipitation plots for LMZ, LMTF and LMTF op. • Summary • Proposal for future developments Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  4. Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  5. EXPERIMENTAL RUN ON FUJITSU (ECMWF) LM CONFIGURATION (version 2.10) Domain size 465 x 385 (previous EuroLM domain) Grid spacing 0.0625 (7 km) Number of layers 35 Time step 10 sec Forecast range 30 hrs Initial time of model run 00 UTC Lateral boundary conditions and initial state Op. IFS (preproc. with CNMCA-IFS2LM) L.B.C. update frequency 3 hrs Orography Filtered (eps = 0.1) + Extra Filtering Prognostic precipitation Off Turbulence parameterization Explicit Prognostic TKE (imode_turb=2) Interval between two calls of turbulence 1 time step Turbulence parameterization R.damping: filter iteration number 10 R. damping: filter length 1 Domain size 234 x 272 Grid spacing 0.0625 (7 km) Number of layers 35 Time step and integration scheme 40 sec , 3 timelevel split-explicit Forecast range 48 hrs Initial time of model run 00/12 UTC Lateral boundary conditions GME L.B.C. update frequency 1 hrs Initial state GME Initialization D. F. External analysis None Status Operational Hardware IBM SP3 (Bologna) N° of processors used 64 LM (3.20+) and LMZ (1.5+) configuration Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  6. 6h Acc.Total Precipitation: LMZ Old code: spline interpolation of phys./dyn. tendencies and imode_turb=2 Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  7. 6h Convective Rain: LMZ Old code: spline interpolation of phys./dyn. tendencies and imode_turb=2 Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  8. Underestimation of Convective Precipitation in LMZ • Error in the trigger of convection, since dqvdt (qv advection + qv vertical turbulent flux) and qvsflx (qv surface flux) not computed • qv vertical turbulent flux for imode_turb=2 (qvtens in turbdiff) added to dqvdt (for imode_turb=1 explicit correction not added; fixed also in LM official code) • qv advection interpolated to physics grid (in swap_tendencies) and added to dqvdt • qvsflx computed (in z_slow_tendencies) • Error in the computation of physical tendencies, since radiation and convection tendencies not added to the other ones (in src_z_leapfrog). Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  9. LMZ on Parallel Machines • Other bugs were found running LMZ on parallel machines: • boundary exchange of wind tendencies in TKE prognostic turbulence scheme missing (only for imode_turb=2 in turbdiff) • uncorrect final index in computation of flux limiters (in fluxlim) • extension of subdomain size for a correct setting of horizontal boundary conditions in cut cells missing (in z_horizontal_advection) • LMZ 1.5 upgrade to LM 3.20 (CIRA performed that one to 3.17) including also the option of the spline interpolation of phys./dyn. tendencies present in LMZ 1.4. Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  10. 6h Acc.Total Precipitation: LMZ Spline interpolation of physical tendencies and imode_turb=2 Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  11. 6h Acc.Total Precipitation: LMZ Linear interpolation of phys./dyn. tendencies and imode_turb=2 Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  12. 6h Acc. Rain: Sp./Lin. Int. Tend. LMZ Convective LMZ (Lin.Int.Tend.) LMZ (Spl.Int.Tend.) Grid-scale Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  13. LMZ Old LMZ 6h Accumulated Rain: Old/New LMZ Convective Grid-scale Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  14. 6h Acc.Total Precipitation: LMTF imode_turb=2 Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  15. 6h Acc.Total Precipitation: LMTF/LMZ LMZ LMTF FC 00-06 h FC 06-12 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  16. 6h Acc.Total Precipitation: LMTF/LMZ LMZ LMTF FC 12-18 h FC 18-24 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  17. 6h Acc.Total Precipitation: LMTF/LMZ LMZ LMTF FC 24-30 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  18. LMZ 6h Accumulated Rain: LMTF/LMZ Convective LMTF Grid-scale Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  19. 6h Acc.Total Precipitation: LMTF (op.) Implicit prognostic TKE turbulence scheme (imode_turb=1) + bug correction Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  20. 6h Acc. Tot. Precipit.: LMTF (op.)/LMZ LMZ LMTF (op.) FC 00-06 h FC 06-12 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  21. 6h Acc. Tot. Precipit.: LMTF (op.)/LMZ LMZ LMTF (op.) FC 12-18 h FC 18-24 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  22. 6h Acc. Tot. Precipit.: LMTF (op.)/LMZ LMZ LMTF (op.) FC 24-30 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  23. LMZ 6h Accum. Rain: LMTF (op.) / LMZ Convective LMTF (op.) Grid-scale Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  24. 6h Acc. Tot. Precipit.: LMTF (op.)/LMTF LMTF LMTF (op.) FC 00-06 h FC 06-12 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  25. 6h Acc. Tot. Precipit.: LMTF (op.)/LMTF LMTF LMTF (op.) FC 12-18 h FC 18-24 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  26. 6h Acc. Tot. Precipit.: LMTF (op.)/LMTF LMTF LMTF (op.) FC 24-30 h Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  27. 6h Accum. Rain: LMTF (op.) / LMTF Convective LMTF (op.) LMTF Grid-scale Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  28. Accumul. Precipitation Comparison LMZ LMTF LMTF op. Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  29. Objective verification results Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  30. Objective verification results ~ 100 events LMTF op. for this case study seems to be better than LMZ. LMTF produces a larger amount of precipitation than LMZ and LMTF. Does the explicit TKE prognostic turbulence scheme work correctly? Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  31. Objective verification results ~ 850 fc-obs Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  32. Summary • Some bugs were fixed in LMZ code for solving the underestimation of convection precipitation and the problems with parallel machines. • The spline interpolation of the dynamical / physical tendencies does not seem to work correctly (spots of very large precipitation). The linear one seems to give satisfying results. • For a case study, LMZ forecasts less and slightly smoother precipitation than LMTF. The amount of accumulated total precipitation of LMTF op. (imode_turb=1) and LMZ are pretty similar. LMTF op. forecasts less convective precipitation than LMTF. • Comparison of surface variable forecasts with observations shows that LMTF op. performs better than LMZ and LMTF. Lucio Torrisi WG2-COSMO GM, Bucharest 2006

  33. Proposal for Future Developments • Wait for new LM 3.21, upgrade LMZ to this version and release new LMZ (1.6?) • Include recent improvements in z-dynamics on the new version • Improve computational efficiency of z-coordinate code • Other: implicit vertical advection, use of implicit turbulence parameterization, microphysics, etc. Lucio Torrisi WG2-COSMO GM, Bucharest 2006

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