PHYSICS IN THE ECMWF MODEL
Anton Beljaars
(Physical Aspects Section)
• Introduction
• Moist processes
– Clouds
– Precipitation
– Fog
• Screen level temperature and humidity
• Surface wind (mean+gusts)
• Boundary layer height
Met. Ops.: Physics
Parametrized processes in the ECMWF model
Met. Ops.: Physics
PHYSICS IN THE ECMWF MODEL
Anton Beljaars
(Physical Aspects Section)
• Introduction
• Moist processes
– Clouds
– Precipitation
– Fog
• Screen level temperature and humidity
• Surface wind (mean+gusts)
• Boundary layer height
Met. Ops.: Physics
The ECMWF cloud parametrization
Convective Detrainment Large-scale ascent
Diabatic cooling Turbulence
Cloud water/ice Cloud fraction
Diabatic heating
Precipitation Turbulence
Cumulus induced subsidence Large-scale subsidence
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Linking clouds and convection
• Basic idea:
– use detrained condensate as a
source for cloud water/ice
– use detrained mass as source
for cloud amount (cover)
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Convective and stratiform precipitation
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Cloud overlap
Example • TCC (total cloud cover). Model
model top level clouds are integrated from
HCC=0.5 surface to top of the atmosphere
using maximum/random overlap
• HCC (high level cloud cover).
450 hPa Integrated from top to 450 hPa.
MCC=0.5
• MCC (medium level cloud cover).
Integrated from 450 to 800 hPa.
• LCC (low level cloud cover).
800 hPa
Integrated from 800 hPa to
surface.
LCC=0
• NOTE:
TCC <= LCC+MCC+HCC
model surface
TCC=0.95
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Effect of new cloud scheme
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Cloud fraction (LITE/ECMWF model)
Model
LITE
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Chilbolton (UK) - CC Model vs. Radar
ECMWF
Observations
ECMWF
Observations
Hogan, Jakob and Illingworth (2000)
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Fog (cloud at lowest model level)
60 hour forecast;
verification time:
13-Oct-1995 00 UTC
For more details see:
Teixeira (1999): Simulation of fog with the
ECMWF prognostic cloud scheme,
Q.J.Roy.Meteor.Soc., 125, 529-551.
Also ECMWF Tech. Memo 225.
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Fog simulation (Cabauw, The Netherlands)
Single column simulation.
For more details see: Teixeira (1999): Simulation of fog with the ECMWF prognostic cloud
scheme, Q.J.Roy.Meteor.Soc., 125, 529-551. Also ECMWF Tech. Memo 225.
Met. Ops.: Physics
PHYSICS IN THE ECMWF MODEL
Anton Beljaars
(Physical Aspects Section)
• Introduction
• Moist processes
– Clouds
– Precipitation
– Fog
• Screen level temperature and humidity
• Surface wind (mean+gusts)
• Boundary layer height
Met. Ops.: Physics
T and q interpolation to the 2m level
q60 T60 • q s and Ts are determined by
level 60 the land surface scheme or by
(10 m) SST.
• Main purpose of land surface
scheme is to provide correct
area averaged fluxes of heat
and moisture.
• Land surface scheme
q2 T2 considers different sub-areas
2m level
(tiles) but effect on screen
(diagnostic)
level variables is not
accounted for yet.
surface
qs Ts
Met. Ops.: Physics
Tiled ECMWF Scheme for Surface Exchange over Land (TESSEL)
• Land tiles:
– High vegetation
– Low vegetation
– Wet surface
– Bare ground
– Exposed snow
– Snow under vegetation
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Diurnal cycle over land
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Cloud cover and 2m-T verification
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History of 2m T-errors over Europe
Met. Ops.: Physics
PHYSICS IN THE ECMWF MODEL
Anton Beljaars
(Physical Aspects Section)
• Introduction
• Moist processes
– Clouds
– Precipitation
– Fog
• Screen level temperature and humidity
• Surface wind (mean+gusts)
• Boundary layer height
Met. Ops.: Physics
10 m wind
• Local wind depends strongly on
woodland grass mountains local exposure.
• ECMWF model has roughness
length parametrization to obtain
realistic “area averaged” surface
drag.
• Resulting wind is low over land
because rough elements dominate.
Post-processing of wind at 10 m
• Post-processed 10 m wind interpolates wind
75 m
from 75 m assuming roughness length for
grassland.
10 m • Note: this exposure correction is only a partial
correction to account for local effects (which
tend to be more complex).
Met. Ops.: Physics
Wind gusts
• WMO defines a gust as the extreme wind after averaging over 3
seconds.
• In ECMWF model turbulence estimate is made of standard
deviation of horizontal wind to simulate gust.
10 m
surface
U Ugust
• (Ugust – U) ~ standard deviation of of wind (turbulence)
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Mean wind (10 m); 42-hour fcst, verifying 20001208 6 UTC
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Gust (10 m); 42-hour fcst, verifying 20001208 3-6 UTC
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PHYSICS IN THE ECMWF MODEL
Anton Beljaars
(Physical Aspects Section)
• Introduction
• Moist processes
– Clouds
– Precipitation
– Fog
• Screen level temperature and humidity
• Surface wind (mean+gusts)
• Boundary layer height
Met. Ops.: Physics
Diagnostic boundary layer height
Troen and Mahrt (1986): v
Find inversion by parcel
lifting with T-excess: vbl
( w' v ' )o / ws (turbulence temperature scale)
hbl
ws {u C1w }
3
*
3 1/ 3
*
vl
g vbl ( vl )
hbl Ricr 0.25
T (U bl U l ) 2
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Profile Nancy (model 24 hour fcst vs. sonde 20000716)
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Profile in March 2003, Germany !!
XXX; Exp. OPER ; 60 lev els
Sonde(blue; 20030325 12) Mod/An(red; 20030323 12 0048)
Lat/Lon (Sonde): 48.10 9.25; Lat/Lon (Model): 48.10 48.10 9.25 9.25
20 30 40 50 60 70 80
12 24 28 400
8 16 20 7136. -32
32 36
6974. -30
6812. -29
4 6650. -27
40 450 6488. -26
6326. -25
6164. -24
6002. -22
5840. -21
10 500 5678. -20
0 5526. -19
5383. -18
5241. -18
5098. -17
550 4961. -17
4825. -16
4693. -15
4560. -13
-4 4429. -13
600 4302. -12
4177. -11
4051. -10
3926. -9
0 3808. -9
650 3690. -8
3573. -7
3455. -7
3337. -6
3220. -5
-8 700 3102. -5
2993. -4
2884.
2776. -4
-4
2673. -3
750 2570. -2
2468.
2365. -1
0
2262. 1
2159. 2
800 2057. 3
-12 1954.
1851. 4
5
-10 1749. 6
850 1646.
1543. 7
8
1450. 9
1356. 9
1262.
1169. 10
11
900 1075.
981. 12
13
887.
796. 14
15
-16 708.
646. 16
16
950
1000
1050
-20
1100
-10 -5 0 5 10 15 20 25 30 35 40 45 50
1.5 2 3 5 7 9 12 16 20 28 36 48 66 80
Met. Ops.: Physics
Boundary layer height
Met. Ops.: Physics
Boundary layer height
Met. Ops.: Physics
Questions
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