Status of ALADIN/ALARO physics

1
Status of ALADIN/ALARO physics

• Current developments Neva Pristov
• Near future plans and further developments
• Jean-Francois Geleyn

2
ALARO-0 physics package - introduction

• continuity improvements
• economical computation
• algorithmic flexibility ? good basis for
  further developments
• numerical challenges

3
Current developments

• Radiation
• Orographic forcing
• Large scale precipitation
• Prognostic turbulent scheme
• Precipitating convection

J-F Geleyn, G. Hello, N. Pristov, Y. Bouteloup,
M. Derkova, J. Masek, A.Trojakova, R. Fournier
B. Carty, F. Bouyssel, R. Brožkova, J-F Geleyn,
M. Derkova, R. Mladek, J. Cedilnik, D. Drvar, I.
Beau
B. Carty, J-F Geleyn, J. Cedilnik, M. Tudor, D.
Drvar
F. Vana, J. Cedilnik, M. Tudor, J-F Geleyn
Luc Gerard, J-M Piriou, I. Stiperski, D. Banciu,
J-F Geleyn
4
Orographic forcing

• modifications in gravity wave parameterization
• implemented already in ALADIN, operational at
  CHMI
• Features
• more consistent definition of wave- and form
  drag- components
• a lift acting (ortogonal) to the geostrophic wind
• replacing of the envelope orography by a mean
  orography
• mountain sub-grid effects are considered also
  down to scales of around 5 km

5
Radiation

• Aim
• using the current delta-two stream approximation
  of radiative transfer equation for solar and
  thermal bands
• economical computation (a good quality cost
  ratio)
• better consideration of clouds
• New features
• new technique for thermal radiative fluxes
  computation on the basis of Net Exchanged Rate
  (NER) formalism
• gaseous transmition functions for computation of
  optical depth closer to RRTM scheme
• introduction of the complete aerosol model
• updating of the cloud optical properties

6
Radiation

• Computation of optical depths using the gazeous
  RRTM transmission functions

7
Radiation cloud optical properties

• problem
• saturation effect on cloud properties
• depends also on properties and geometry of
  cloud layers above and below
• aim
• to parameterize the saturation effect
• taking into account cloud overlaping option
• profit from prognostic cloud water and ice

8
Radiation cloud optical properties

• Validation method
• create idealized cloud simulation model to get
  reference values
• comparision for transmissivities and
  reflectivities
• for a homogeneous single cloud
• for the impact of non-homogeneity (3 layers)
• for the impact of non-uniformity (3 layers, still
  simple exercise)

9
Radiation cloud optical properties

• Current
• scheme

solar band
thermal band
transmissivities
homogeneous clouds
reflectivities
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Radiation cloud optical properties
New scheme
solar band
thermal band
transmissivities
homogeneous clouds
reflectivities
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Radiation cloud optical properties
New scheme
solar band
thermal band
transmissivities
non-homogeneuos clouds
reflectivities
12
Radiation cloud optical properties
New scheme
solar band
thermal band
transmissivities
non-uniformity clouds
reflectivities
13
Large scale precipitation

• Aim
• using the benefit of the good tuning of current
  scheme
• better space distribution of precipitation (less
  upslope, more downslope precipitaton)
• Features
• a simple micro-physics scheme with 5 water phases
  included into precipitation scheme
• cloud water, cloud ice, liquid, solid
  precipitation - new prognostic variables
• water vapour
• all phase-changes go through the vapour phase
• only rain and snow leave the particle of the air
• all non-precipitating species have the same
  vertical velocity

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Large scale precipitation

• pseudo fluxes
• condensation/evaporation (transfer between vapour
  and liquid water)
• auto conversion (transfer between liquid and rain
  water)
• evaporation of precipitation (transfer between
  rain and vapour water)
• freezing/sublimation (transfer between vapour
  water and ice)
• auto conversion (transfer between ice and snow)
• sublimation of the falling snow (transfer between
  snow and vapour water)
• treatment of rain and snow
• link between flux and mean fall-speed (new)
• collection (4 cases)
• evaporation
• melting/freezing
• sedimentation of precipitation (new)

15
Prognostic turbulent scheme

• Aim
• to extend the current vertical diffusion scheme
  to be compatible with the general and more
  physical (AROME) TKE scheme.
• using the benefit of the current vertical
  diffusion scheme (known properties, tuning and
  stability issues)
• Requirements
• modularity - allowing gradual conversion to a
  full TKE scheme
• time stability - combination of the two implicit
  schemes (dissipation and self-transport),
  anti-fibrillation treatment
• Features
• the turbulent memory of the previous timesteps is
  kept
• the advection and diffusion of TKE is added to
  the current scheme
• more general computation of mixing length
  (planed)

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Precipitating convection

• aim
• convection at grey zone
• combining relevant and subgrid contribution to
  cloud condensation and precipitation
• basis
• the version of the scheme developed by Luc
  Gerard, including the MT (microphysics and
  transport) idea of Jean-Marcel Piriou and
  enhanced by the current interfacing and
  modularising work of Ivana Stipersky gt
• Acronym 3MT (Modular Multi-scale Microphysics
  and Transport)

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Precipitating convection

• Luc Gerald
• the convection is extincting gradually with the
  resolution increase
• convection does not produce precipitation itself
  the updraught detrains cloud condensates,
  which are put into micro-physics scheme together
  with resolved condensed part
• prognostic convective closure
• Jean-Marcel Piriou
• proposed method can in principle handle dry,
  non-precipitating or precipitating convection.
• the convective tendencies are expressed directly
  in terms of micropysics and transport, based on
  the concept of Buoyant Convective Condensation
  (BCC) rate
• the closure assumption can shift continuously
  from a CAPE behaviour to a humidity convergence
  behaviour

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Precipitating convection

• ALARO
• adapt to micro-physics scheme and thermodynamics
• diagnostic/historic/prognostic closure
• compatibility with the vertical diffusion
• treatment of the diagnostic coudiness

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Future evolutions and perspectives

• Short term actions
• - further optimise mountain drag-lift scheme
• - search the best option of the pseudo-TKE
  numerics
• - tuning of auto-conversion
• More ambitious actions
• - capitalise on the transversal aspects of 3MT
• - optimise the grey-zone use
• - intermittent use of the NER-based radiation
• - unified cloud definition and use
• - non-precipitating convection use of 3MT

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Capitalising on the transversal aspects of 3MT

• Open topics (with only a preliminary answer in
  the ALARO-0 solution)
• Rate of convective entrainment
• Computation of up- downdrafts vertical
  velocities
• Convective closure assumption
• Prognostic, historic or diagnostic aspect of the
  3 previous items
• Pseudo-adiabatic type computations for convective
  ascending and subsiding motions
• Dynamical characteristics of those ascending
  and subsiding motions
• Source term for convective friction
• Microphysical terms (except sedimentation).

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Optimising the grey-zone use (upon a good start)

• Situation of 10 Septembre 2005 (results obtained
  par Luc Gerard)
• Urban flooding in Brussels in the afternoon
• The oper ALADIN-Belgique did not forecast much
  rainfall
• Forecasting from the 12 UTC network for the
  period 18-19 UTC
• Results compared to radar accumulations for one
  hour (max 70 mm) same colour scale.

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The first prototype is encouraging (1/3)
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The first prototype is encouraging (2/3)
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The first prototype is encouraging (3/3)
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Modified proposal (extreme case with 8 fields to
store)
Intermittent use of the NER-based radiation
Complete comput. in clear sky
Complete comput. in clear sky
N ?t
Flux ??? LW SW
etc.
Interpolation
?opt, ?, ? gaz (8 x)
For the ALARO case else, who wants
?t modèle
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Unified cloud definition and use

• In ALARO-0, the cloudiness used for radiation and
  moist vertical diffusion will still be
  diagnostic and the prognostic one of LGs
  scheme (coming from both condensation
  computations) will input only microphysics.
• In the future, the latter will also be passed to
  the next time step and used for all purposes,
  after experimentation and tuning have shown this
  is safe for all possible weather types.

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Non-precipitating convection use of 3MT

• In the M-T proposal of J-M Pirious thesis one
  central paradigm is reversed rather than
  impliciting the microphysics (stationary cloud)
  and expliciting the detrainment (closure), one
  does the opposite.
• This is achieved by separating microphysics and
  transport terms.
• But this idea can in principle be extended to
  non-precipitating (and even dry) convection with
  seamless transitions (next 3 dias).
• A huge unifying potential to explore as soon as
  feasible!

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Modélisation 2 Equations convectives
proposition MT-CCB Perspective historique des
équations convectives à échelle résolue

(Q1c réchauffement convectif, Q2c assèchement
convectif fois L)
Transport
Condensation nette
GATE (1974), Arakawa-Schubert (1974), Bougeault
(1985), Tiedtke (1989), Fritsch-Chappell (1980),
Kain-Fritsch (1990), KF-Bechtold (2001),
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Modélisation 2 Equations convectives
proposition MT-CCB Equations convectives à
échelle résolue proposition MT-CCB

(Q1c réchauffement convectif, Q2c assèchement
convectif fois L)
Dans lapproche MT-CCB plus besoin de
paramétriser le détraînement à échelle
résolue. Réalisme du schéma reporté sur celui de
sa microphysique.
Transport
Condensation nette
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Modélisation 2 Equations convectives
proposition MT-CCB Equations convectives à
échelle résolue proposition MT-CCB

Synergie méthodologique
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Conclusions

• We cannot yet prove anything but we are rather
  confident to reach the short term objectives of
  the action (continuity, innovation and numerical
  safety/efficiency).
• If this is indeed the case, there will be a huge
  potential of joint development (around a few
  hopefully acceptable basic choices). In the end,
  further success will depend on the attractivity
  of this concept.