Pre-operational testing of Aladin physics

1
Pre-operational testing of Aladin physics

• Martina Tudor1, Ivana Stiperski1, Vlasta Tutiš1,
  Dunja Drvar1 and Filip Vana2
• 1 Meteorological and Hydrological Service, Gric
  3, Zagreb, Croatia
• 2 Czech Hydrometeorological Institute, Na Šabatce
  16, Prague, Czech Republic

2
Outline

• Methods
• orography and GWD parameterization
• radiation and cloudiness
• horizontal diffusion
• Case studies
• Summary

3
Orography and GWD

• envelope has been removed from orography
• modified GWD
• introduced lift
• tested on a set of bura cases

4
Envelope vs. mean orography

• model orography with envelope (left), mean
  orography (center) and their difference (right)

5
14th November 2004, 10m wind 42 hour forecast in
the oper (left) and experimental (centre) model
version, and their difference (right), for the
8km (top) and 2km resolution (bottom)
6
New GWD scheme and new orography

• old GWDenvelope orography (left),old GWDmean
  orography, new GWDmean orography
• what has stronger influence on the prognosed wind
  field new GWD scheme or new orography?

7
Comparison to measurements

• 10m wind forecast is compared to the 10m wind
  measurements giving good (left), bad (center) and
  ambiguous (right) results

8
Summary of the results

• Removal of the envelope and changes in gravity
  wave drag parametrization result in
• stronger winds on the windward and generally
  weaker winds on the leeward side of the obstacle,
  as expected
• Mountain wave amplitude is reduced and smoothed
• Sub-grid scale orography representation has
  bigger impact on the results than modified
  gravity wave parametrization

9
Radiation and cloudiness

• Random, random maximum and maximum cloud overlap
  assumptions,
• Different critical relative humidity profiles
  (old and new)
• Cloudiness schemes
• Operational
• Xu-Randall (1996)
• Radiation schemes
• Operational
• Operational including net exchange rate
  formulation (NER)
• FMR scheme (Morcrette, 1989) called with
  different intervals.

10
The fog case

• Meteosat-8 RBG composite of channels 3.9, 10.8
  and 12.0 µm for December 15th 2004, 06 UTC. Fog
  or low clouds over Southeastern Europe are
  clearly visible.

11
Low, medium and high cloudiness

• with operational radiation (left and right) and
  NER (center), random overlap (left and right) and
  random maximum overlap (center) using operational
  (left) and Xu-Randall cloudiness scheme with new
  critical relative humidity profile (center and
  right), 30 hour forecast starting 00 UTC 14th
  December 2004.

12
Low, medium and high cloudiness

• Low, medium and high cloudiness, with FMR
  radiation scheme called with 3 hr interval (left)
  and 1hr interval (center and right), with maximum
  (center) and random overlap (right) and
  Xu-Randall cloudiness scheme with new critical
  humidity profile, 30 hour forecast starting 00
  UTC 14th December 2004.

13
Comparison to measurements
reference rand max rmnew RH XR cloud random old
RH
max, 1hr r-max, 1hr rand, 1hr max, 3hr r-max,
3hr rand, 3hr

• Comparison of the modelled 2m temperature
  evolution for 00 UTC run on 14th December 2004
  with measured data from synoptic station with
  operational radiation scheme (left) including NER
  (center) and FMR (right).

14
Radiation and cloudiness results

• New relative humidity profile only slightly
  increases low cloudiness.
• Random maximum overlap significantly reduces the
  amount of clouds and amplified the diurnal
  variation of temperature when compared to the
  random overlap results.
• Xu-Randall cloudiness scheme gives more clouds
  and improves 2m temperature forecast.
• More sophisticated radiation schemes did not
  improve results.
• The parameterization of cloudiness seems more
  important than the radiation parameterization for
  better forecast of 2m temperature.

15
SLHD

• Numerical horizontal diffusion is applied along
  model level that follows orography, so it is not
  purely horizontal.
• Significance of physical diffusion increases with
  horizontal resolution,
• in situations with strong horizontal wind shear
  and statically stable situations,
• is more pronounced in cyclogenetic areas like
  Adriatic Sea.
• Near orography model levels are more tilted,
  horizontal diffusion acts more along the
  vertical.
• Horizontal mixing occurs between valleys and
  mountaintops- cloud forming on mountaintop
  instead of fog in the valley.

16
Twin cyclones

• Meteosat-8 infra-red image for January 26th
  2005, 06 UTC.
• Cyclones over Tyrhennian and Adriatic Sea.

17
Twin cyclones
numerical diffusion
SLHD

• 10m wind and mean sea level pressure obtained
  with numerical diffusion (top left), SLHD (top)
  and their difference (left), 48 hour forecast
  starting from 00 UTC 24th January 2005.

difference
18
Twin cyclones
numerical diffusion
SLHD
difference

• AT850 and wind obtained with numerical diffusion
  (top left), SLHD (top) and their difference
  (left), 48 hour forecast starting from 00 UTC
  24th January 2005.

19
Fog case

• Meteosat-8 RBG composite of channels 3.9, 10.8
  and 12.0 µm for December 15th 2004, 06 UTC.

20
Fog case

• Low, medium and high cloudiness, numerical
  diffusion (left) and SLHD (right), 30 hour
  forecast starting from 00 UTC 14th December 2004.

21
Comparison to data

• Comparison of the modelled 2m temperature
  evolution for 00 UTC run on 14th December 2004
  with measured data from synoptic station

reference NER LRAUTOEV SLHD mean orog SLHDm.o.
22
Summary

• Semi-Lagrangian Horizontal Diffusion (SLHD) shows
  beneficial impact on the
• reduction of the overestimated cyclone intensity,
• correction of cyclone position while not altering
  a good intensity prediction,
• improvement of fog forecast in the valleys