Transcript Kein Folientitel

Introducing the Lokal-Modell LME
at the German Weather Service
Jan-Peter Schulz
Deutscher Wetterdienst
27th EWGLAM and 12th SRNWP Meeting 2005
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
Modifications from LM to LME
• 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
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•
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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
• 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
Multi-Layer Soil Model
In order to demonstrate the capabilities of the new multilayer 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.
Soil temperature without freezing/melting
°C
4
3
2
1
0
-1
-2
-3
-4
T_SO 1
T_SO 2
T_SO 3
-5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time [h]
14
15
16
17
18
19
20
21
22
23
24
Soil water content without freezing/melting
mm
20
18
16
14
12
10
8
6
4
2
W_SO 1
W_SO 2
W_SO 3
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time [h]
14
15
16
17
18
19
20
21
22
23
24
Soil temperature with freezing/melting
°C
2,5
2
1,5
1
0,5
0
-0,5
-1
T_SO 1
T_SO 2
T_SO 3
-1,5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time [h]
14
15
16
17
18
19
20
21
22
23
24
Soil water content with freezing/melting
mm
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
W_SO 1
W_SO 2
1
W_SO 3
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time [h]
14
15
16
17
18
19
20
21
22
23
24
Soil ice content with freezing/melting
mm
3,5
3
2,5
2
1,5
1
0,5
W_SO_ICE 1
W_SO_ICE 2
W_SO_ICE 3
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Time [h[
14
15
16
17
18
19
20
21
22
23
24
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.
Behaviour of the SMA (07 June 2005)
Moisture
increment by SMA
2-m temperature forecast error
Upper soil layers
Lower soil layers
Behaviour of the SMA (07 June 2005)
Solar net radiation at the ground
Total cloud cover
Behaviour of the SMA (07 June 2005)
Solar net radiation at the ground
Moisture change
(increment) during
the model
forecast
Upper soil layers
Lower soil layers
Soil moisture
Experiments at DWD
Comparison of operational weather forecasts of LM and
LME.
LM
LME
LME
GME
March 2005, 00 UTC forecasts
LME domain (land and sea)
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.
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.
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.