Physics developments in ALADIN: towards higher resolution

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Physics developments in ALADINtowards higher
resolution

• Neva Pristov
• Environmental Agency of Slovenia
• Meteorological office

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Content

• Cloudiness
• Orographic forcing
• Radiation
• Microphysics and convection

T. Haiden, A. Kann, H. Seidl, R. Brokova, ...
B. Carty, F. Bouyssel, R. Brokova, J-F Geleyn,
M. Derkova, R. Mladek, J. Cedilnik, D. Drvar
J-F Geleyn, G. Hello, N. Pristov, Y. Bouteloup,
M. Derkova
Luc Gerard
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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

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Low cloudiness sensitivity experiment
horizontal diffusion of temperature - on
Seidl/Kann scheme Improved stratus forecast, but
areal coverage still insufficient
horizontal diffusion of temperature - off
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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

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Cloudiness
Total cloudinessprevious
new
Amount of clouds is more realistically
distributed
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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

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Orographic forcing
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

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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

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Orographic forcing
Total precipitation sum 62 days SOP MAP 1999

• Bias reduced by 25
• Maxima around moutains peaks decreased
• No improvement in distribution

Analyses
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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

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Radiation

• CTSEWSEBL decomposition of the thermal
  radiative
• exchange terms in absence of scattering

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Radiation
Scores with respect to FMR (new ARPEGE)
Geopotential Better on all domains
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Radiation
Scores with respect to FMR (new ARPEGE)
Temperature Better for Europe and N20 (except at
very top) Worse for Tropics and S20
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Radiation

• Computation of optical depths using the gazeous
  RRTM transmission functions

CTS
EWS
EBL
Comparison of fluxes encouraging results
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Combined effects of improvements
Storm 14 September 2003 Black Sea MSL pressure
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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

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Microphysics and convection

• Comparision of 2 experiments
• Precipitating
• Water condensing in the updraught is immediately
  precipitated to the ground
• Integrated
• Updraught detrains condensates

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Microphysics and convection

• Squall line 14 August 1999 Western Belgium
• MSL pressure and precipitation

precipitating
integrated
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Microphysics and convection

• Squall line 14 August 1999 Western Belgium

precipitating
integrated
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Microphysics and convection
Vertical cross section cloud condensates and T
integrated
precipitating
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Microphysics and convection
Vertical cross section updraught vertical
velocity
integrated
precipitating
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Microphysics and convection

• Problem
• Not enough precipitation
• because of vertical distribution of
  condensates
• Solution
• Detrainment connected with
• Entrainment by the same cloud at lover level
• Neighbourhood clouds

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• Additional effort is needed