status of aladin/alaro p hysics

Hirlam-aladin workshop Oslo, December 2005

Status of ALADIN/ALARO physics

Current developments: Neva Pristov

Near future plans and further developments:

Jean-Francois Geleyn


ALARO-0 physics package - introduction

• continuity + improvements

• economical computation

• algorithmic flexibility good basis for further developments

• numerical challenges


Current developments

• Radiation

• Orographic forcing

• Large scale precipitation

• Prognostic turbulent scheme

• Precipitating convectionLuc GerardLuc Gerard, J-M Piriou, I. Stiperski, D. Banciu, , J-M Piriou, I. Stiperski, D. Banciu, J-F GeleynJ-F Geleyn

J-F Geleyn, G. Hello, N. Pristov, Y. Bouteloup, J-F Geleyn, G. Hello, N. Pristov, Y. Bouteloup, M. DerkovaM. Derkova, J. Masek, A.Trojakova, J. Masek, A.Trojakova, R. Fournier, R. Fournier

B. Carty, F. Bouyssel, R. Brožkova, J-F Geleyn, B. Carty, F. Bouyssel, R. Brožkova, J-F Geleyn, M. Derkova, R. Mladek, J. Cedilnik, D. Drvar, I. BeauM. Derkova, R. Mladek, J. Cedilnik, D. Drvar, I. Beau

B. Carty, J-F Geleyn, J. Cedilnik, B. Carty, J-F Geleyn, J. Cedilnik, M. Tudor, M. Tudor, D. DrvarD. Drvar

F. Vana,F. Vana, J. Cedilnik, J. Cedilnik, MM. . Tudor, Tudor, J-F GeleynJ-F Geleyn


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


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


Radiation

• Computation of optical depths using the gazeous RRTM transmission functions

0

10

20

30

40

50

60

70

0,00E+00 1,00E-01 2,00E-01 3,00E-01 4,00E-01 5,00E-01

zuueot rrtm

ZUUEOT acraneb

0

10

20

30

40

50

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70

0.00E+00 2.00E-02 4.00E-02 6.00E-02 8.00E-02 1.00E-01

zdeot rrtm

ZDEOT acraneb

0

10

20

30

40

50

60

70

0,00E+00 2,00E-01 4,00E-01 6,00E-01 8,00E-01 1,00E+00

zeolt rrtm

ZEOLT acraneb

Comparison of fluxes in the thermal radiation

CTS EWS EBL


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 optionprofit from prognostic cloud water and ice



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)



Current scheme

reflectivities

transmissivities

homogeneous clouds

solar band thermal band



Newscheme

reflectivities

transmissivities

homogeneous clouds




Newscheme

reflectivities

transmissivities

non-homogeneuos clouds




Newscheme

reflectivities

transmissivities

non-uniformity clouds



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


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)


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)


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 =>

Acronym: 3MT (Modular Multi-scale Microphysics and Transport)



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



ALARO:

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


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


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).


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.


The first prototype is encouraging (1/3)

The simulation converges realistically when resolution

increases. There is hardly any sign of a ‘grey zone’ syndrome.

x=9.9 kmx=7.0 km

x=4.0 kmx=2.2 km



CV

on off

9.9 km

CV

on off

2.2 km

Convection auto-extinguishs itself at increased resolution, and furthermore ...



Convective precipitations Stratiform precipitations2.2 km

… even at the meso- scale, at the heart of convective cells, there is still as much parameterised precipitations as resolved

ones (and the tool giving this result seems reliable for this problem).

CV LS TotalLS seul

0 32 33 50 64Max. precip.


Modified proposal (extreme case with 8 fields to store)

Completecomput.

inclear sky

Completecomput.

inclear sky

Flux

LW & SW

‘Interpolation’

opt, , gaz (8 x)

etc.

Model of opt Clouds + Aerosols

ACRANEB-82nd part

Fluxes ofthe time-

step

To ‘import / reframe’

Done (ALADIN2)

Exists !

In progress

t modèle

N t

For the ALARO case ; else, who wants …

Intermittent use of the NER-based radiation


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 LG’s 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.


Non-precipitating convection use of 3MT

• In the M-T proposal of J-M Piriou’s 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!


Modélisation 2: Equations convectives: proposition MT-CCBModélisation 2: Equations convectives: proposition MT-CCB

Perspective historique des équations convectives à échelle résoluePerspective historique des équations convectives à échelle résolue


Perspective historique des équations convectives à échelle résoluePerspective historique des équations convectives à échelle résolue

(Q1c: réchauffement convectif, Q2c: assèchement convectif fois L)(Q1c: réchauffement convectif, Q2c: assèchement convectif fois L)

Bilan nuageux stationnariséBilan nuageux stationnarisé

Condensation netteCondensation nette

TransportTransport

Bougeault (1985):Bougeault (1985):

Pseudo-subsidence, détraînement uniforme et soustr. turbulencePseudo-subsidence, détraînement uniforme et soustr. turbulence

Yanai (1973):Yanai (1973):

Pseudo-subsidencePseudo-subsidence

Détraînement à échelle résolueDétraînement à échelle résolue

GATE (1974), Arakawa-Schubert (1974), Bougeault (1985), Tiedtke GATE (1974), Arakawa-Schubert (1974), Bougeault (1985), Tiedtke (1989), Fritsch-Chappell (1980), Kain-Fritsch (1990), KF-Bechtold (1989), Fritsch-Chappell (1980), Kain-Fritsch (1990), KF-Bechtold

(2001), …(2001), …



Equations convectives à échelle résolue: proposition MT-CCBEquations convectives à échelle résolue: proposition MT-CCB



(Q1c: réchauffement convectif, Q2c: assèchement convectif fois L)(Q1c: réchauffement convectif, Q2c: assèchement convectif fois L)

MT-CCBM & T couplés:

Condensation netteCondensation nette

TransportTransport

MT-CCB:

Condensation Convective BruteCondensation Convective Brute

Evaporation des gouttes nuageusesEvaporation des gouttes nuageuses

Evaporation des gouttes de pluieEvaporation des gouttes de pluie

TransportTransport

Chal. sens. précip.Chal. sens. précip.

Dans l’approche MT-CCB plus besoin de Dans l’approche MT-CCB plus besoin de paramétriser le détraînement à échelle paramétriser le détraînement à échelle

résolue.résolue.

Réalisme du schéma reporté sur celui de sa Réalisme du schéma reporté sur celui de sa microphysique.microphysique.






MT-CCB:MT-CCB:

Microphys. Vit. vert., ferm.

CVPCVP CVNPCVNP CV sècheCV sèche

Continuité de la microphys.

Synergie méthodologique

Air humide, CVPAir humide, CVPYanai (1973)Yanai (1973)

Bougeault (1985)Bougeault (1985)

Simpl. de la microphys.

CRM, LESCRM, LES

Complexif. de la microphys.


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.

status of aladin/alaro p hysics

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