Formation

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Jean-Marcel Piriou Centre National de Recherches
Météorologiques Groupe de Modélisation pour
lAssimilation et la Prévision
Update on model developments Meteo-France NWP
model / clouds and turbulence
CLOUDNET workshop / Paris 27-28/05/2002
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Summary

• How may 1D studies improve 3D models? Example of
  the EUROCS project, links with CLOUDNET
• Clouds and turbulence present developments and
  perspectives of the ARPEGE/ALADIN NWP model

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Global ARPEGE Aquaplanet mode
SCM ARPEGE (EUROCS, GATE, TOGA,BOMEX, ARM, )
Global regular ARPEGE / 4DVAR-ass. / 100 km
PHYSICS
LAM ALADIN / coupled / 10 km
Global stretched ARPEGE / 4DVAR-ass. / 20 to 200
km
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Diurnal cycleof convection / JJA
Observations Yang and Slingo MWR 2001
ARPEGE NWP Model J.M. Piriou 2002
IFS NWP Model Beljaars 2002
Unified Climate Model Yang and Slingo MWR 2001
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EUROCS EUROpean Cloud Systems
3-year project funded by the European Union (Mar
2000 Feb2003)
Final aims to improve the treatment of cloud
systems in global and regional climate
models Links with GCSS (GEWEX Cloud System Study)
for more infos www.cnrm.meteo.fr/gcss/EUROCS/EURO
CS.html J.-L. Redelsperger
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Diurnal cycle of deep convection(Françoise
Guichard, Météo-France)
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COMMON CRMs/SCMs CASE STUDY
1 an  observed case  to assess our
models over land (GCSS/ARM)
Southern Great Plains

• GCSS WG4 Case3a
• 4-day runs with deep convection occuring
• large-scale advections prescribed from
  observations
• fixed surface heat fluxes
• wind nudged towards observed
• cyclic lateral boundary conditions
• case part of the GCSS intercomparaison exercise
  for
• CRMs Xu et al. (2002) SCMs (Xie et al. 2002)

2 building an  idealized case  to
address the diurnal cycle of deep
convection over land and its representation in
models
ARM Atmospheric Radiation measurement
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THE IDEALIZED CASE

• same framework of previous case except
• 27 Mai 1997 of GCSS case 3 repeated twice
• large-scale vert. adv. (relatively weak)
  prescribed surf. fluxes
• 48 h run, begins in the morning instead of the
  evening

results still preliminary, work in progress

• rainfall events tend to occurs earlier in SCMs
  than CRMs (2 SCMs missing)
• similar findings (e.g., noise no or weak
  downdraughts)

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THE IDEALIZED CASE transition regimes
transition phase not represented in several
SCMs
snapshots of cloud rain water content in CRM run
a  shallow  non-precipitating transition period
which last a few hours in CRMs
before the development of deep convection
15 km
Lx 300 km
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THE IDEALIZED CASE CIN

• almost no CIN in SCM runs during daytime (true
  for at least 4 SCMs) !
• apparently not simply a resolution problem

• challenging for CRMs too
• strongly modulated by convective activity
• in CRMs runs, deep convection increases the CIN
• possibly related to convective downdraughts (?)

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CONCLUSIONS from diurnal cycle of deep convection
case

• deep convection often occurs earlier than
  observed in SCMs runs too
• no succession of dry-shallow-deep regimes in
  SCMs, dry to deep directly
• complex sensitivity to triggering criteria
  downdraughts formulation
• no CIN during daytime weak downdraughts ( a
  link?)

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Diurnal cycle of shallow cumulus (Geert
Lenderink, KNMI)
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(No Transcript)
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(No Transcript)
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EUROCS Marine stratocumulus case(Peter
Duynkerke, IMAU)
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EUROCS marine stratocumulus case
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Perspectives for the ARPEGE/ALADIN physics

• March towards new prognostic cloud and turbulence
  variables ql/i, qr/s, TKE, w_ud, w_dd
• EUROCS 4 validation cases (next 12 months)
• CLOUDNET colocated ql/i, qr/s, PBL depth,
  cloudiness, close TEMP data to provide in-situ
  validation of new microphysics / turbulence (in
  some months?)

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Conclusions / perspectives

• During the last years 1D studies have become more
  and more important to develop and validate 3D
  models physical packages
• Both EUROCS (well posed lateral conditions) and
  CLOUDNET (long time series) will be used as a
  test-bed for the new cloud physics and turbulence