Physics developments in ALADIN: towards higher resolution

October 2004 26th EWGLAM, Oslo Page: 1

Physics developments in ALADIN:towards higher resolution

Neva PristovEnvironmental Agency of Slovenia

Meteorological office


Content

• Cloudiness

• Orographic forcing

• Radiation

• Microphysics and convectionLuc GerardLuc Gerard

J-F Geleyn, G.J-F Geleyn, G. Hello, N.Hello, N. Pristov, Y.Pristov, Y. Bouteloup, M.Bouteloup, M. DerkovaDerkova

B.B. Carty, F.Carty, F. Bouyssel, R.Bouyssel, R. Brožkova, J-F Geleyn, Brožkova, J-F Geleyn, M.M. Derkova, R.Derkova, R. Mladek, J.Mladek, J. Cedilnik, D.Cedilnik, D. DrvarDrvar

T.T. HaHaiiden, den, A. Kann, H. Seidl, A. Kann, H. Seidl, R.R. BrožkovaBrožkova,, ... ...


Cloudiness

• Problem Underestimating of low cloudiness Structure of lifted inversions poorly predicted Overestimated diurnal cycle of temperature

• Method Experiments (1-d and 3-d) with different cloudiness

parameterizations Study effects of vertical diffusion parameterization on

inversion


Low cloudiness sensitivity experiment

horizontal diffusion of temperature - on

horizontal diffusion of temperature - off

Seidl/Kann scheme

Improved stratus forecast, but areal coverage still insufficient


Cloudiness

Scheme modifications modify the vertical profile of critical relative

humidity - to get medium and high clouds starting to appear at lower relative humidity values.

tuning of the X-R function in Xu-Randall cloudiness scheme

use of the random/maximum overlap for clouds instead of the random overlap


Cloudiness

Amount of clouds is more realistically distributed

Total cloudinessprevious new


Orographic forcing

• modification in orography drag parametrization revised dependencies of the drag on the Froude

number a lift orthogonal to the geostrophic wind and not

any more to the real wind

• replacing envelope orography by a mean orography


Orographic forcing

10km

5km 2.5km 1.25km

Experiments (Experiments (Semi-Academical)) on ALPIA domain

Using new drag/lift scheme• The new scheme is tuned to be resolution independent

• Parameterization is needed for horizontal mesh sizes from ~ 5 km

• The envelope can be suppressed by the new lift scheme

• The thin line between param / no param is not clear


Orographic forcing

envelope disappearance and drag/lift improvement

+ more realistic flow around the mountain ranges

+ better wind scores at 850 hPa and around

+ less upwind exaggerated precipitations on mountain flanks (unfortunately) without any shift in position,

+ increased compatibility with the theory of sub-grid mountainous forcing,

- too weak 10 m winds near mountains

- decreased foehn effect that was apparently well tuned before,

- slightly negative upper air geopotential scores


Orographic forcing

Total precipitation

sum 62 days SOP MAP 1999

Analyses

Mean orography, new drag scheme

Difference

Envelope orography, old drag scheme

Difference

• Bias reduced by 25%

• Maxima around moutains peaks decreased

• No improvement in distribution


Radiation

completely modifies the thermal computations

2 modes:

• 'statistical' - 'basic' call at each time-step;

• 'self-learning' - some chosen time steps are far more expensive to better tune the 'classical' ones used in-between


Radiation

CTS+EWS+EBL decomposition of the thermal radiative

exchange terms in absence of scattering

CTS

EWS

EBL


Radiation

Scores with respect to FMR (new ARPEGE)

Geopotential

Better on all domains


Radiation

Scores with respect to FMR (new ARPEGE)

Temperature

Better for Europe and N20

(except at very top)

Worse for Tropics and S20


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

60

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 – encouraging results

CTS EWS EBL


A- 986 hPa

Combined effects of improvements

B- 1000 hPa

Cloudiness, radiation, drag, without envelopeCloudiness, radiation, drag, without envelope+ SLHD

C- 1007 hPa

Storm 14 September 2003 Black Sea

MSL pressure


Microphysics and convection

An integrated approach

• Microphysics 3 prognostic: vapour, cloud ice, cloud liquid water 2 diagnostic: precipitation liquid and solid Fluxes of water and heat Parametrization of WBF and riming process

• Convective updraught detrains condensates (no precipitation)

• Downdraught



Comparision of 2 experiments

• Precipitating Water condensing in the updraught is

immediately precipitated to the ground

• Integrated Updraught detrains condensates



Squall line 14 August 1999 Western Belgium

MSL pressure and precipitation

‘precipitating’ integrated



Produce less precipitationProduce less precipitationMaximum of precipitation on right placeMaximum of precipitation on right placeSmoother pressure fieldSmoother pressure field

‘precipitating’ integrated

Precipitation continues to increasePrecipitation continues to increase

Squall line 14 August 1999 Western Belgium



More cloud iceMore cloud ice

integrated‘precipitating’

Vertical cross section – cloud condensates and T



integrated‘precipitating’

Vertical cross section – updraught vertical velocity

Extended updraught activityExtended updraught activityHigher velocitiesHigher velocities



Problem

• Not enough precipitation

because of vertical distribution of condensates

Solution

• Detrainment connected with Entrainment by the same cloud at lover level Neighbourhood clouds


Additional effort is needed

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Physics developments in ALADIN: towards higher resolution

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