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Dynamical downscaling of wind fields in stratified flow: a high
resolution mesoscale approachPedro Miranda, R Tomé, A Rodrigues, J Palma,
F Castro, J Pinto, E Dutra
University of Lisbon, CGUL, IDL, PortugalUniversity of Porto, CEsA, Portugal
Issues
Merging meteorology and mechanical engineering approaches to wind simulation
What resolution is needed/possible to get the most from mesoscale meteorological models?
Is it worth using even higher resolution nested CFD codes?
Forecast and mapping: how different are they?
What is in a weather prediction model?
• Resolved scales: full dynamic equations (hydrostatic or non-hydrostatic)Problems
• initial state, boundary conditions• interaction with unresolved scales (higher-resolution?)• misrepresentation of non-dynamical processes
• Unresolved scales and processes• Orography (small and some mesoscale)> local wind• Clouds• Turbulence• ...
D1 [ 81 km x 81 km ]
D2
D2 [ 27 km x 27 km ]
D3
D3 [ 9 km x 9 km ]
D4
D4 [ 3km x 3 km ]
D5
D5 [ 1 km x 1 km ]
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
m
ECMWF (T511L60~40km) 3km
Models
MeteorologicalBoundary conditions from ECMWF analysis
MM5 (nested, down to 33, 22 or 11 km), full physics, 5 years54x54km18x18 6x6 (3x3 or 2x2 or 1x1)
WRF (nested domains, down to 22 km), full physics, 1 month
MesoNH (nested domains, down to 22 km), full physics, 1 month
NH3D (single domain, 1.51.5km), simple physics
CFD codeBoundary Conditions from NH3D
VENTOS, dry, unrotating, adiabatic, ~300300 m, 1 week
-17.3 -17.2 -17.1 -17 -16.9 -16.8 -16.7
M esoN H 2x2
32.6
32.7
32.8
32.9
20
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
-17.3 -17.2 -17.1 -17 -16.9 -16.8 -16.7
M esoN H 2x2
32.6
32.7
32.8
32.9 “Real”100x100m
Model2x2km
ResolutionP 1
P 2
P 3
5 7 9 11 13 15
x (km )
12
14
16
18
20
y (k
m)
303429342834
29332833
2832 2932
3033
3032
1316
-10 -5 0 5 10
x (km )
5
10
15
20
y (k
m) P 1
P 3
P 2
3km1.5km
10 15 20 25 30
-6
-4
-2
0
2
4
6
8
10
u (
m/s
)
dia
P1 P3034 nh3d
10 15 20 25 30
-14
-12
-10
-8
-6
-4
-2
0
2
4
v (m
/s)
dia
P1 P3034 nh3d
u
v
2001-2005
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
16
18
20
Mod
el
Observation
3km: r=0.40, y=0.77x2km: r=0.66, Y=1.15x1km: r=0.58, y=1.10x
Resolution (MM5)
0 5 10 15 20 25 30
0
5
10
15
20
25
30
win
d P32
2
November 2005
OBS30 MesoNH30 WRF27 MM5a36
Best mast (Nov 2005)
Nov 2005 Models (MM5, WRF, MesoNH) @2km
0 2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
16
18
20
Mod
el
Observation (P322)
MM5: r=0.66, y=1.15xWRF: r=0.68, y=1.00xMesoNH: r=0.78, y=0.88x
Coupling NH3D (1.5km) with VENTOS (300m)
0 5 10 15 20 25 300
5
10
15 obs30 MM5x36 Ventos NH3d
win
d P
1
June 2001
-17.4 -17.3 -17.2 -17.1 -17 -16.9 -16.8 -16.7 -16.6
W RF
32.5
32.6
32.7
32.8
32.9
33
-17.4 -17.3 -17.2 -17.1 -17 -16.9 -16.8 -16.7 -16.6
M M 5
32.5
32.6
32.7
32.8
32.9
33
-17.5 -17.4 -17.3 -17.2 -17.1 -17 -16.9 -16.8 -16.7 -16.6 -16.5
M esoNH
32.5
32.6
32.7
32.8
32.9
33
33.1
Nov 2005Mean wind2x2km
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
Final thoughts
Results are model dependent and resolution dependent (same analysed boundary conditions)
“High” mesoscale resolution is needed (e.g. 2km)
There may be gains in higher resolution (100m) if the microscale model is good
There is a clear need for improvement!
Remember: this is a very rough case in terms of topography. Results in mainland Portugal are often better