Pre-operational testing of Aladin physics

Martina Tudor1, Ivana Stiperski1, Vlasta Tutiš1, Dunja Drvar1 and Filip Vana2

1 Meteorological and Hydrological Service, Grič 3, Zagreb, Croatia2 Czech Hydrometeorological Institute, Na Šabatce 16, Prague, Czech Republic

Ljubljana, 3-5 October 2005 27th EWGLAM & 12th SRNWP meeting 2

Outline

• Methods– orography and GWD parameterization– radiation and cloudiness– horizontal diffusion

• Case studies

• Summary

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Orography and GWD

• envelope has been removed from orography

• modified GWD

• introduced lift

• tested on a set of bura cases

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Envelope vs. mean orography

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

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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)

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New GWD scheme and new orography

• old GWD+envelope orography (left),old GWD+mean orography, new GWD+mean orography

• what has stronger influence on the prognosed wind field: new GWD scheme or new orography?

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Comparison to measurements

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

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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

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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.

Ljubljana, 3-5 October 2005 27th EWGLAM & 12th SRNWP meeting 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.

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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.

Ljubljana, 3-5 October 2005 27th EWGLAM & 12th SRNWP meeting 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.

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• 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).

Comparison to measurements

referencerand maxrm+new RHXR cloudrandomold RH

max, 1hrr-max, 1hrrand, 1hrmax, 3hrr-max, 3hrrand, 3hr

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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.

Ljubljana, 3-5 October 2005 27th EWGLAM & 12th SRNWP meeting 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.

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Twin cyclones

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

Adriatic cyclone

Tyrhennian Sea

please, ignore this oneit is outside of the domain

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Twin cyclones

• 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.

numerical diffusion SLHD

difference

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Twin cyclones

• 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.

numerical diffusion SLHD

difference

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Fog case

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

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Fog case

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

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Comparison to data

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

referenceNERLRAUTOEVSLHDmean orogSLHD+m.o.

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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