Introducing the lokal modell lme at the german weather service
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Introducing the Lokal-Modell LME at the German Weather Service. Jan-Peter Schulz Deutscher Wetterdienst 27 th EWGLAM and 12 th SRNWP Meeting 2005. The expansion of the LM domain has been requested by the following (internal) DWD customers:. LME: LM Europe. Aviation consulting

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Introducing the lokal modell lme at the german weather service
Introducing the Lokal-Modell LMEat the German Weather Service

Jan-Peter Schulz

Deutscher Wetterdienst

27th EWGLAM and 12th SRNWP Meeting 2005


The expansion of the lm domain has been requested by the following internal dwd customers
The expansion of the LM domain has been requested by the following (internal) DWD customers:

LME: LM Europe

  • Aviation consulting

  • Sea traffic consulting

  • Particle dispersion modelling


Modifications from LM to LME following (internal) DWD customers:

  • Number of grid points per layer enhanced from 325 x 325 to 665 x 657, mesh size unchanged at 7 km x 7 km


Lme lm europe
LME: LM Europe following (internal) DWD customers:

  • Model Configuration

    Grid spacing: 0.0625° (~ 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


Modifications from LM to LME following (internal) DWD customers:

  • Number of grid points per layer enhanced from 325 x 325 to 665 x 657, mesh size unchanged at 7 km x 7 km

  • Number of layers increased from 35 to 40. 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


Configuration of the New Multi-Layer Soil Model following (internal) DWD customers:


Multi layer soil model
Multi-Layer Soil Model following (internal) DWD customers:

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.


Variational soil moisture analysis sma
Variational Soil Moisture Analysis (SMA) following (internal) DWD customers:

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.


Behaviour of the sma 07 june 2005
Behaviour of the SMA (07 June 2005) following (internal) DWD customers:

Moisture increment by SMA

Upper soil layers

Lower soil layers

2-m temperature forecast error


Behaviour of the sma 07 june 20051
Behaviour of the SMA (07 June 2005) following (internal) DWD customers:

Solar net radiation at the ground

Total cloud cover


Behaviour of the sma 07 june 20052
Behaviour of the SMA (07 June 2005) following (internal) DWD customers:

Moisture change (increment) during the model forecast

Upper soil layers

Lower soil layers

Solar net radiation at the ground


Soil moisture
Soil moisture following (internal) DWD customers:


Experiments at dwd
Experiments at DWD following (internal) DWD customers:

Comparison of operational weather forecasts of LM and LME.


LM following (internal) DWD customers:

LME


LME following (internal) DWD customers:

GME

March 2005, 00 UTC forecasts

LME domain (land and sea)


Verification results
Verification results following (internal) DWD customers:

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.


Conclusions
Conclusions following (internal) DWD customers:

  • 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.


Conclusions1
Conclusions following (internal) DWD customers:

  • 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.


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