status of the cosmo-1 configuration at meteoswiss guy de morsier

Federal Department of Home Affairs FDHAFederal Office of Meteorology and Climatology MeteoSwiss

Status of the COSMO-1 configuration at MeteoSwiss

Guy de Morsier

COSMO-GM, Roma, 5.9.2011

2 COSMO-GM, Roma / Sept. 2011 / Status of the COSMO-1 configuration at MeteoSwiss Guy de Morsier

Agenda

• Motivation

• Status of the ARPA-SIM collaboration

• Domain and orography filtering

• Namelist choices

• Some results

• Summary

• Future


Motivation for COSMO-1

• Operational target is for 2015• Why increase the grid resolution?

- improve representation of forcing (e.g. topography, land use)

- better capture non-linear interaction between different scales (e.g.

convection)

- improve use of observing systems in the assimilation step

• Focus mainly on Alpine region and Alpine specific problems


Target: COSMO-1 suite in 2015

8x dailyCOSMO-1 +24 hours forecasts

1 km grid size, 100 layers

1040 x 700 grid pointsIFS boundary conditions 10 km grid size, 140 layers

4x daily


Status of the ARPA-SIM collaboration

√ Common domain• Test if a common configuration can be used and

a common evaluation of results operated• Nesting strategy

compare C-1 in C-7 with C-1 in C-2• Decrease damping in upper layers

cf. Wolfgang Langhans1)• Tune the orographic filtering to the stability of the

dynamics• Investigate the sensitivity to the asymptotic turbulent

length scale and the vertical level distribution

1) Convergence of numerical simulations of linear hydrostatic gravity wave, March 11, 2011


1) eXtra filter only for masked high Steps of Orography

Orography filtering (2 extremes)

Rhône V.

Rhine

COSMO-1COSMO-2COSMO-7

4 x Raymond filter + XSO1) 750m


Gradient of orography

a) NO filter, max.36°, mean 6°

b) Std filter, max.25°, mean 4.4°

c) 400m xso, max.20°, mean 4.2°

d) 300m xso, max.18°, mean 3.8°

Compare (CH) to:

COSMO-7: max.4°, mean 1.1°!

COSMO-2: max.15°, mean 2.8° near Mt Blanc

a) b)

c) d)

y

habs

x

habshgrad *5.0)(


Large Alpine Domain698 x 528 gridpoints

CPU of COSMO-2 * 4

300m filter: max. gr. 18°C-1 with 750m filter: 25°

COSMO-2: 15°


3“C-2

Orographic spectra


Namelist choicesBold for C-2 operational RED = C-1

Dynamics• time step (t=10sec, C-2=20)• advection (SL, Bott2, l3dstrang, lva_impl_dyn)• If possible NO horizontal diffusion• divergence damping (xkd=0.1/0.05/0.01)

best choice: • upper boundary condition (nrdtau=5/2)

*t: e-folding time for damping at the model top

Physics• turbulence (itype_turb=3)


COSMO-1 cases

A. Storm Carmen 12 November 2010with different orographic smoothingneeds horizontal diffusion (1 slide)

B. Convective case 29 May 2010with/without horizontal diffusiondifferent advection codes

C. Stratus case of 27 October 2009 without horizontal diffusion (no slides)


A. Energy spectra CARMEN (12.11.2010)

24h forecast (u, v, w)from 6 to 10km height

Similar results for smaller time steps

with hor. dif.


B. Convective case with COSMO-1

hd_corr_u_in=0.5 NO horizontal diffusion


Test with a modified advection (U. Blahak)

~ 15 m/s !

Maximum nur noch ~ 3 m/s !



NO horizontal diffusionUli Blahak modif. advection



001: Uli Blahak modif. advection

003: NO horizontal diffusion

002: with horizontal diffusion

[ m

3 ]



NOhorizontal

diffusion (hd)

NO hdbut with

UB modif.advection

Withhorizontaldiffusion

Time series of Max. vertical wind Max. horizontal wind


B. Convective case 29 May 2010

24h forecast (u, v, w)from 6 to 10km height


Summary

• Choice of the orographic filtering is not too bad considering the spectral evaluationbut depends on the model dynamics

• Stable run can produce meaningless values (horizontal wind) at some particular time

• Possible to run cases without horizontal diffusion

• The advection scheme has an impact on the results( more tests needed!)


Future

• Set up an assimilation cycle for COSMO-1

• Regular runs from the assimilation cycle

• Evaluate against COSMO-2

• Need more test cases and/or case studies:- Convection- Stratus- Strong precipitation- Föhn

status of the cosmo-1 configuration at meteoswiss guy de morsier

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