Lucio Torrisi WG2-COSMO GM, Bucharest 2006

Recents Improvements in LMZ Code

Lucio TORRISI

CNMCA – Pratica di Mare (Rome)

l.torrisi@meteoam.it

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

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

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

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

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

LM (3.20+) and LMZ (1.5+) configuration

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMZ Old code: spline interpolation of phys./dyn. tendencies and imode_turb=2

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Convective Rain: LMZ Old code: spline interpolation of phys./dyn. tendencies and imode_turb=2

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

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

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

6h Acc.Total Precipitation: LMZSpline interpolation of physical tendencies and imode_turb=2

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMZLinear interpolation of phys./dyn. tendencies and imode_turb=2

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Rain: Sp./Lin. Int. Tend. LMZ

LMZ (Lin.Int.Tend.)

Convective

Grid-scale

LMZ (Spl.Int.Tend.)

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

Old LMZ LMZ

6h Accumulated Rain: Old/New LMZConvective

Grid-scale

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMTF imode_turb=2

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMTF/LMZ LMTF LMZ

FC 00-06 h

FC 06-12 h

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMTF/LMZ

FC 12-18 h

FC 18-24 h

LMTF LMZ

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMTF/LMZLMTF LMZ

FC 24-30 h

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Accumulated Rain: LMTF/LMZ

LMZLMTF

Convective

Grid-scale

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc.Total Precipitation: LMTF (op.)Implicit prognostic TKE turbulence scheme (imode_turb=1) + bug correction

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Tot. Precipit.: LMTF (op.)/LMZLMTF (op.) LMZ

FC 00-06 h

FC 06-12 h

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Tot. Precipit.: LMTF (op.)/LMZ

FC 12-18 h

FC 18-24 h

LMTF (op.) LMZ

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Tot. Precipit.: LMTF (op.)/LMZLMTF (op.) LMZ

FC 24-30 h

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Accum. Rain: LMTF (op.) / LMZ

LMZ

Convective

Grid-scale

LMTF (op.)

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Tot. Precipit.: LMTF (op.)/LMTFLMTF (op.) LMTF

FC 00-06 h

FC 06-12 h

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Tot. Precipit.: LMTF (op.)/LMTF

FC 12-18 h

FC 18-24 h

LMTF (op.) LMTF

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Acc. Tot. Precipit.: LMTF (op.)/LMTFLMTF (op.) LMTF

FC 24-30 h

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

6h Accum. Rain: LMTF (op.) / LMTFConvective

Grid-scale

LMTF (op.) LMTF

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

Accumul. Precipitation Comparison

Domain mean (max) 30 hr total precipitation

1.667 (177.1) 2.933 (177.5) 1.863 (110.4)

Domain mean (max) 30 hr grid-scale rain

.7413 (51.4) 1.004 (140.2) .9212 (96.5)

Domain mean (max) 30 hr convective rain

.9138 (176.9) 1.889 (110.1) .9075 (62.3)

LMZ LMTF LMTF op.

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

Objective verification results

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

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 LMZand LMTF.Does the explicit TKE prognostic turbulence scheme workcorrectly?

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

Objective verification results

~ 850 fc-obs

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

• 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.

Summary

Lucio Torrisi WG2-COSMO GM, Bucharest 2006

• 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.

Proposal for Future Developments