Status of AROME Physics
Sylvie Malardel
Yann Seity, Gwenaëlle Hello, Christine Lac,
Valery Masson, Patrick Lemoigne et al
Météo-France/CNRM et Laboratoire
d’aérologie
1
AROME
Aladin dynamical
core
2
AROME Physics
 Current ECMWF radiation scheme called every 15
min (F.M. for SW and RRTM for LW)




Microphysics (vapor+5 hydrometeors)
Turbulence (CBR, pronostic TKE)
Shallow convection (KFB)
+ a subgrid representation of clouds
 Externalised surface
 Isba
 Simple schemes for sea and lakes
 TEB
3
The Daily Arome prototype
This Arome is running
every day on different domains
MIDPYR since june 2005,
SUDE since september 2005
Replaced by NORE this winter
(plots on ALADIN2 WebSite)
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AROME domains over FRANCE
PARI
BRET
NORE
MIDPYR
SUDE
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Deep Clouds
•Microphysics
•Coupling with the dynamics
6
An AROME good forecast : 21 June 2005
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21 June 2005 Case
21
24
15
18
12TU
TU
TU
Inst. AROME rainfalls
L41 AROME wind
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21 June 2005 Case
15 TU
AROME coupled with
Aladin oper
AROME coupled with
Aladin 3DVAR
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Microphysical retrievals : IOP 2A (intense convection)
Simulation (Meso-NH)
12 km
Deep clouds
(x) hail + graupel
(o) hail
( ) rain
(x) hail + graupel
Z > 60
dBz
graupel
(o) hail
( ) rain
100 km
Tabary, 2002
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Deep clouds
Microphysical retrievals : IOP 3 (moderate convection)
18:10 UT
dry snow
hail + graupel
rain
18:30 UT
hail + graupel
snow
rain
Meso-NH simulation
Pujol et al., 2005
11
Deep clouds
Quasi-stationnary MCS 13-14 Oct. 1995
OBSERVATIONS
MESO-NH,x=2.5km
x=10km
MESO-NH,
m
m
MESO-NH, x=2.5km
mm
max
max: : 99
25 mm
mm
Initialisation Ducrocq
et al (2000)’s
max : 135 mm
max: 31 mm
Initial conditions: ARPEGE analysis at 18UTC
Cumulated precipitation 01 UTC to 06 UTC the 14th Oct. 1995
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(Ducrocq et al, 2002)
Deep clouds
 As Méso-NH, Arome is able to simulate correctly the organisation
of mesoscale convective organisation
 Sensitivity to coupling and initial condition
For AROME in 2006
 Use diagnostics to evaluate more objectively and statisticaly
precipitating events
 Adaptation of numerical aspects of the sedimentation
parametrization (time splitting) to longer time steps (> 60s)
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Fog (and low clouds)
•Microphysics
•Radiation
•Vertical resolution
•Turbulence in stable layers
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First case of Fog : 7 January 2005
09 TU
AROME 2 last levels cloud
cover
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First case of Fog : 7 January 2005
15 TU
AROME 2 last levels cloud
cover
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Fog
just a few studies with Meso-NH …
But A PRIORITY for AROME
Scientist
Bergot et al., 2005, submitted :
Intercomparison of 1D numerical
models for prediction of the fog
( mp, turbulence, z)
2 events at Paris-CdG. 4 sets of initial
conditions (RS): 18UTC (onset), 21
(thickening), 00 (mature) and 03
(disspation)
Model
Levels
<50m
Levels
<200m
E.Terradellas
Hirlam-INM
(1D version
used in Spain)
1
3
O. Liechti
tBM
2
7
N.W. Nielsen
Hirlam-DMI
13
20
T. Bergot
Cobel-Isba
13
20
M. Mueller
Cobel-Noah
18
30
J.Cuxart/A.Mira
MesoNH
50
89
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Cumulated liquid water content
Fog
Crude test : Modification of the
autoconversion threshold
Meso-NH without
sedimentation of
small droplets
Initialization at 03UTC
Late dissipation due to excessive
rc : lack of gravitational settling
Meso-NH
with
sedimentation
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Bergot et al., 2005, submitted
Fog
For AROME in 2006

Microphysics : Implementation of the sedimentation for
small droplets

Tests on the sensitivity to vertical resolution  Additional
levels to L41 ? (Cobel-Isba with L41 shows degradation)

Evaluation on CAPITOUL and on several international
airports. Run of AROME on Ile-de-France on winter 2005
and in 1D on Casablanca and Varsovie (to be confirmed)
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Convective boundary layers
and stratocumulus
•Shallow convection
•Turbulence
•Subgrid clouds
•Microphysics
•Surface
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2005/08/20
09 TU
AROME
Meso-NH
with
SUBGRID
COND +
SHALLOW :
Adjustment
time of 3h in
the closure
Meso-NH
with
SUBGRID
COND +
SHALLOW
30min :
Adjustment
time of
30min
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Coupling with Aladin oper (r0)
Bomex :
w'
'
l
  3h
LES
  1h
w*
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ARM :
LES
  1h
w'
'
l
  3h
w*
23
ARM : cloud mixing ratio
  3h
LES
  1h
w*
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BL clouds : Cu
For AROME in 2006
1.
Modification of the KFB closure (w*, Grant et al, 1999)
2. Improvement of subgrid cloud representation (Bechtold
et al, 1995, Lenderink and Siebesma, 2000)
3. Test of EDMF scheme in Meso-NH (P.Soares)
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Stratocumulus : What’s about the resolutions of AROME ?
x= y= 500m
LES
Cloud water mixing ratio
0h LT
12hLT
SCM
0hLT
0h LT
12hLT
0hLT
x= y= 2.5km
I.Sandu
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BL clouds : Sc
Liquid Water Path
x=500m,z=25m
x=500m,z=50m
x=500m,z=80m
LES
x=500m,z=10m
I. Sandu
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BL clouds : Sc
Preliminary tests in Meso-NH at the resolutions of AROME

Diurnal cycle of Sc is maintained at the resolution of Arome

LWC more sensitive to lower z than lower x

Main impact of z at the top of Sc (entrainment) than beneath
For Arome , second part of 2006

Sensitivity tests on vertical resolution for cloud-top
entrainmentAdditional levels to L41?

Interest of an entrainment parametrization (Lock, 2001, 2004. ARPEGEClimat).
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Evaluation CARBOEUROPE
Dry CBL
Forecasts of Meso-NH
(8km) in an operational
mode during the
experiment
La Cape Sud : Comparison MesoNH/RS of BL height (parcel method)
between 6 and 17UTC
25-may
Boundary Layer Height
MESONH vs RS La Cape Sud
26-may
27-may
2500
31-may
06-june
simulated
2000
Weak overestimation
during
the afternoon
07-june
08-juin
09-juin
1500
10-juin
MESO-NH vs PIPER
1000
Weak underestimation during
the morning
500
0
0
500
1000
1500
observed
2000
2500
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Dry CBL
BUT limitations are well-known,
inherent to Eddy-diffusivity
Eddy-diffusivity (local) :
w' '   K

z
with
K

2
L e3
3C p
Too sharpe
inversion due to
lack of topentrainment
Too unstable
1.
The K-diffusion doesn’t take into account countergradient.
2.
Entrainment is not treated explicitly in the K-diffusion approach.
3.
But diffusion remains necessary, for transition to neutral or stable BL.
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Dry CBL
1. Countergradient with Third order moments
On L
2L
1L
On the TOMs
2L with TOMs
2L without TOMs
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Dry CBL
1.
For AROME in 2006
TOMs on heat momentum fitted on LES already implemented in
Meso-NH  evaluation of the impact for AROME on CBL (needs
of evaluation on test cases, impact on unreal rolls ?)
2. EDMF scheme : evaluation of the impact in Meso-NH during the
1st sem.2006 (In collaboration with P.Soares)
3. Comparison EDMF/TOMS on the same cases
Under development in Meso-NH (2006-2008)
1.
Improvement of EDMF scheme : entrainment, extension to momentum
transport (In collaboration with P.Soares in 2006)
2. Parametrization of TOMs with an entraining plume used to find the
mass-flux.
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3. Improvement of the BL89 mixing length in the same way (V.Masson)
Summary
• An Arome daily prototype has been running for 6
months (without any blow up)
• Some good forcasts and some less good (but only
qualitative and episodic validation)
• Some imperative improvement have to be done
quickly on the physics before more serious
validation
– Shallow convection and subgrid clouds
– Fog dissipation
• Numerical improvement : SL sedimentation
• Other preoccupations : Sc, Dry BL etc
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