04/19/23 - 1 -COSMO Workpackage No. 5.1.8

First Results on Verification of LMK Test Runs

Basing on SYNOP Data

Lenz, Claus-Jürgen; Damrath, Ulrichclaus-juergen.lenz@dwd.de; ulrich.damrath@dwd.de

04/19/23 - 2 -COSMO Workpackage No. 5.1.8

Overview

• survey on LMK test runs performed

• verification results

• summary and outlook

04/19/23 - 3 -COSMO Workpackage No. 5.1.8

Survey on LMK experiments performed (1)

- center of model area 10° E, 50° N

- 421 x 461 grid points horizontally

- grid length: 2.8 km

- 50 vertical layers, height of lowest layer: 40 m, height of lowest half level: 22 m above ground

- values for initialisation and boundaries from operational LM run

04/19/23 - 4 -COSMO Workpackage No. 5.1.8

Survey on LMK experiments performed (2)

testsuites performed for winter (Januar 2004)

experiment time integrationscheme, timestep

horizontaladvectionscheme

calculation ofprecipitation

thermo-dynamics

relaxation at lateralboundaries

673 leapfrogΔt = 16 s

centered2. order

diagnostic advection ofT=T0+T*

tanh function, implicit,similar to LM

683 TVD-RK 3. orderΔt = 30 s

upwind5. order

prognostic advection ofT=T0+T*

tanh function, as in LM,precipitation diagnostic

687 TVD-RK 3. orderΔt = 30 s

upwind5. order

prognostic advection ofT*=T-T0

cos function, explicit,precipitation diagnostic

688 TVD-RK 3. orderΔt = 30 s

upwind5. order

prognostic advection ofT*=T-T0

cos function, explicit,precipitation diagnostic,relaxation von qv, qcund qi

04/19/23 - 5 -COSMO Workpackage No. 5.1.8

Survey on LMK experiments performed (3)

testsuites for summer (July 2004) und autumn (September 2004)

- time integration: TVD Runge-Kutta 3. order, time step: Δt = 30 s- scheme for horizontal advection: upwind 5. order- prognostic calculation of precipitation- thermodynamics: advection of T=T0+T*- relaxation at lateral boundaries: explicit formulated cosine function

exp. parameterisationof shallowconvection

lateral boundaryvalues for pressure

precipitation scheme,number of classes

dataassimilation

advectionof qx

689 no interpolation 5 classes no Euler-forw.

696 yes vertical integration 5 classes no Euler-forw.

698 yes vertical integration including graupel6 classes

no Euler-forward

701 yes vertical integration 5 classes yes Euler-forw.

709 yes vertical integration including graupel6 classes

yes Semi-Lagrange

713 yes vertical integration including graupel6 classes

yes Bott-2-scheme

04/19/23 - 6 -COSMO Workpackage No. 5.1.8

LM and LMK:

TSS precipitation rates

> 0.1 mm/h (top left),

> 2 mm/h (top right),

> 10 mm/h (left)

January 2004, 00 h runs

04/19/23 - 7 -COSMO Workpackage No. 5.1.8

Frequency Bias (FBI) for

coverage due to low clouds

July 2004, 00 h runs

cloud coverage <= 2/8

cloud coverage >= 6/8

04/19/23 - 8 -COSMO Workpackage No. 5.1.8

Bias (mean error) for 2 m temperature, July 2004, 00 h runs

04/19/23 - 9 -COSMO Workpackage No. 5.1.8

LM and LMK:

TSS for precipitation rates

> 0.1 mm/h (top left),

> 2 mm/h (top right),

> 10 mm/h (left)

September 2004, 00 h runs

04/19/23 - 10 -COSMO Workpackage No. 5.1.8

Bias (mean error) for 2 m temperature, September 2004, 00 h runs

04/19/23 - 11 -COSMO Workpackage No. 5.1.8

sensitivity of TSS for precipitation

with respect to Latent Heat Nudging

07 - 19 July 2004, 12 h runs

prec. > 0.1 mm/h prec. > 2 mm/h

prec. > 10 mm/h

04/19/23 - 12 -COSMO Workpackage No. 5.1.8

sensitivity of TSS for precipitation with respect to interpolation method

LMK, experiment 701

September 2004, 12 h runs

prec. > 0.1 mm/h prec. > 2 mm/h

prec. > 10 mm/h

04/19/23 - 13 -COSMO Workpackage No. 5.1.8

Summary:

- gusts (not shown here): enhanced forecast accuracy in LMK due to finer grid resolution

- precipitation: results of the smaller scale model lead to partly better verification results than the LM routine forecast

- different tests (e.g. introduction of a parameterization scheme for shallow convection, data assimilation) lead to higher accuracy for some parameters, but other parameters may be affected negatively

- interpolation method during verification: higher TSS values at small precipitation rates and lower TSS values at higher precipitation rates using a larger averaging area than the nearest grid point

04/19/23 - 14 -COSMO Workpackage No. 5.1.8

Outlook:

- further continuous work on verification of past and future LMK experiments

- development of a tool for application of conditional verification is ongoing

- calculation of synthetic radar images using the radar simulation model by Haase (1998)

- verification of LM and LMK using the synthetic radar images