1. Development of a three-dimensional short range forecast model
Meteorologisches Institut der Universität Bonn
Auf dem Hügel 20, Bonn
                        
Development of a three-dimensional
short range forecast model
of fog and visibility
Matthieu MASBOU & Andreas BOTT
COST 722 intercomparaison meeting – 25 June Paris

2. Work environment
Parameterized
microphysics
First tests
&
outlooks

3. Forecast models at DWD 2 deterministic numerical models
Synoptic scale global model GME
Mesoscale model LM (Lokal-Modell)

4. Lokal-Modell (LM) Limited-area model
Model area: Western and Central Europe
Mesh size: 7km
Number of gridpoints: 325x325x35
Time step: 40sec
48 hours forecast

5. Physics Non hydrostatic compressible model for the mesoscale
Radiation
Non hydrostatic compressible model for the mesoscale
Moist diabatic processes
Parameterizations (describe subscale processes via gridscale variables)
Gridscale precipitation (rain or snow from gridscale clouds)
Convection (cumulus clouds, thunderstorms, showers)
Radiation (short-wave solar radiation, long-wave terrestrial radiation)
Boundary layer processes (lowest 1-2 km that are affected by friction, stability of the atmosphere, turbulence)
Soil processes (energy and moisture fluxes between soil and atmosphere)
Convection
Clouds
Turbulence
Soil processes

6. Our forecast area
Determination of a new microscale version of the LM :
325x325x35
(7 km)
50x50x35
(1km)
Boundary fields from the operational LM forecast fields
Rescaling of the vertical axis
Smaller grid boxes near the surface
Use of the multilayer soil grid structure :
Zs = 0.01, 0.04, 0.1, 0.22, 0.46, 0.94, 1.90 m

7. Parameterized microphysics
Comes from PAFOG (Bott & Trautmann 1997) :
Activation : Twomey relation
C and k depend on aerosol type
S supersaturation
Condensation/evaporation :
- Parameterization of Köhler equation (Chaumerliac & al. 1987)
- Fixed Lognormal distribution for the cloud droplet radius
Sedimentation :
with
Viscosity
Reynolds number
- Advection Scheme (Bott 1989)

8. Focus our work on a LM-PAFOG Model and its validation
First tests
Comparison between PAFOG and LM-PAFOG :
- LM-PAFOG : periodic boundaries and homogeneous fields
- Large temperature difference in the soil
Parameterization for soil modules very different
Moreover, different parameterizations of radiation and turbulence
Focus our work on a LM-PAFOG Model and its validation

9. First results of our 3D fog model Meteorological situation :z
Meteorological situation :
Fog and low clouds
Encouraging results :
Our model produces
low clouds too
Time evolution of a Qc profile at hours

10. Outlooks VALIDATION STAGE INTERCOMPARISON STAGE
Short range :
Sensitivity study of our 3D fog model with the data of the Lindenberg
Observatory (Germany)
VALIDATION STAGE
Comparison of our 3D fog model with the data of CDG airport
INTERCOMPARISON STAGE
Then :
Development and implementation of a new spectral microphysical fog module
Verification of the spectral microphysical fog model LM-MIFOG
Development and implementation of the new parameterized fog module
Verification of new parameterized fog model LM-PAFOG
Efficient fog forecast for airport, highways, ...