1. Introducing the Lokal-Modell LME at the German Weather Service
Jan-Peter Schulz
Deutscher Wetterdienst
COSMO General Meeting 2005

2. LME: LM Europe
The expansion of the LM domain has been requested by the following (internal) DWD customers:
Aviation consulting
Sea traffic consulting
Particle dispersion modelling

3. Modifications from LM to LME
Number of grid points per layer enhanced from 325 x 325 to x 657, mesh size unchanged at 7 km x 7 km

4. LME: LM Europe Model Domain of LME Model Configuration
Grid spacing: ° (~ 7 km)
665 x 657 grid points per layer
40 vertical layers
Timestep: 40 sec
Daily runs at 00, 12, 18 UTC, +78h
Boundary Conditions
Interpolated GME forecasts with
ds ~ 40 km and 40 layers (hourly)
Hydrostatic pressure at lateral
boundaries
Data Assimilation
Nudging analysis scheme
Variational soil moisture analysis
SST analysis at 00 UTC
Snow depth analysis every 6 hrs
Model Domain of LME

5. Modifications from LM to LME
Number of grid points per layer enhanced from 325 x 325 to x 657, mesh size unchanged at 7 km x 7 km
Number of layers increased from 35 to Lowest model layer now 10 m above ground (before: 34 m)
Coordinate system rotated differently. LME grid points do not exactly match with LM grid points (important for post processing).
Forecast period enhanced from 48h to 78h
New multi-layer soil model with solution of heat conduction equation, inclusion of the effects of freezing/melting of soil water and improved snow model
Planned operational introduction: 28 September 2005

6. Configuration of the New Multi-Layer Soil Model

7. Multi-Layer Soil Model
In order to demonstrate the capabilities of the new multi-layer soil model the following forecasts were carried out:
24 November 2004, 00 UTC + 24h.
1. Without freezing/melting of soil water
2. With freezing/melting of soil water
The grid point Essen (Germany) is considered. Shown are the soil temperature T_SO, the soil water content W_SO and the soil ice content W_SO_ICE.

13. Variational Soil Moisture Analysis (SMA)
The SMA is active in LME since 3 May 2005, 00 UTC.
Before switching on the SMA in LME the verification results for 2-m temperature were of lower quality for LME than for LM.
Meanwhile, the verification results for LME improved continuously, as expected, and have reached the level of the LM results.

14. Behaviour of the SMA (07 June 2005)
Moisture increment by SMA
Upper soil layers
Lower soil layers
2-m temperature forecast error

15. Behaviour of the SMA (07 June 2005)
Solar net radiation at the ground
Total cloud cover

16. Behaviour of the SMA (07 June 2005)
Moisture change (increment) during the model forecast
Upper soil layers
Lower soil layers
Solar net radiation at the ground

17. Experiments at DWD
Comparison of operational weather forecasts of LM and LME.

20. LM
LME

21. LME domain (land and sea)
GME
March 2005, 00 UTC forecasts
LME domain (land and sea)

22. Verification results
There is positive trend in the simulated precipitation amount during the forecasts of LME which is not present in LM or the global model GME. Furthermore, when comparing LME and GME it turns out that evaporation over sea is considerably higher in LME.
Therefore, an LME experiment has been carried out
where evaporation over sea is reduced by adjusting
one parameter in the surface layer scheme.

27. Kinetic Energy

28. Kinetic Energy

29. Conclusions
LM and LME give generally very similar forecasts on the LM domain.
But in some cases the LME solution deviates from the LM solution and the weather given by the driving model. LME is more able to develop its own weather regime in the interior of the model domain.
Objective verification shows some advantages for LME gusts, but some disadvantages for mean sea level pressure and 2-m temperature. The latter can be explained by the fact that the SMA was not active in LME in this period.

30. Conclusions
There is a positive trend in the simulated precipitation amount during the forecasts of LME.
This trend can be substantially reduced by reducing evaporation over sea. By this, atmospheric water vapour content is decreased which leads to less intense cyclogenesis. This improves the negative bias in surface pressure.
Atmospheric kinetic energy is increasing during LME forecasts. This may be a hint that sub-grid scale orographic effects still need to be considered in LME (like in GME).