Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.
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Transcript of Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.
![Page 1: Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.](https://reader036.fdocuments.in/reader036/viewer/2022062619/5515f97e550346a2308b4896/html5/thumbnails/1.jpg)
Ewan O’Connor, Robin Hogan, Anthony Illingworth
Drizzle comparisons
![Page 2: Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.](https://reader036.fdocuments.in/reader036/viewer/2022062619/5515f97e550346a2308b4896/html5/thumbnails/2.jpg)
Overview– Do operational forecast models simulate drizzle correctly?
• Models simulate drizzle through precipitation scheme• Treat coalescence drizzle as light rain
– Observed liquid water content/flux• Cloud LWC retrieval• Drizzle liquid water flux retrieval
– Compare observations and models• Daily basis• Monthly means
– Drizzle drop size• Explicit in Met Office model• Effect of changing drizzle number concentration
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Liquid water contentMethod of Albrecht et al. (1990), Boers et al. (2000)
– Use lidar/radar to determine cloud boundaries– Assume linear increase of LWC with height– Scale LWC profile to match LWP from radiometers
LWC
Heig
ht
Cloud base(lidar)
Cloud top (radar)
Modellevels
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Liquid water content– LWC not retrieved in rain
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Drizzle below cloudDoppler radar and lidar - 4 observables (O’Connor et al. 2005)
• Radar/lidar ratio provides information on particle size
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Drizzle below cloudDoppler radar and lidar - 4 observables (O’Connor et al. 2005)
• Radar/lidar ratio provides information on particle size
Retrieve three components of drizzle DSD (N, D, μ).• Can then calculate LWC, LWF and vertical air velocity, w.
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Liquid water flux– LWF retrieved below cloud base and in the absence of rain
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ECMWF model– Cloud similar to observations
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Met Office mesoscale model– Cloud similar to observations
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Met Office global model– Has rain at correct time!
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Meteo France ARPEGE model– Thin layers - can be one grid box thick
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Compare obs/models– Models have similar LWC / LWP– Models overestimate precipitation
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Compare daily means– Models have similar LWC / LWP– Models overestimate precipitation
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Monthly comparisons
– ECMWF model– Observations
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Monthly comparisons
– Met Office mesoscale model– Observations
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Monthly comparisons
– Met Office global model– Observations
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Monthly comparisons
– Meteo France ARPEGE model– Observations
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Drizzle drop size– Met Office model uses explicit size distributions– Treats all precipitation as rain
• Overestimates drop sizes • Underestimates evaporation
Disdrometer
Radar/lidar
Model
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Met Office diagnostic precipitation
– Met Office model uses explicit size – Treats all precipitation as rain
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Met Office diagnostic precipitation
– Met Office model uses explicit size– Treats all precipitation as rain
![Page 21: Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.](https://reader036.fdocuments.in/reader036/viewer/2022062619/5515f97e550346a2308b4896/html5/thumbnails/21.jpg)
Met Office diagnostic precipitation
– Met Office model uses explicit size– Treats all precipitation as rain
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Met Office diagnostic precipitation
– Met Office model uses explicit size– Treats all precipitation as rain
![Page 23: Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.](https://reader036.fdocuments.in/reader036/viewer/2022062619/5515f97e550346a2308b4896/html5/thumbnails/23.jpg)
Met Office diagnostic precipitation
– Met Office model uses explicit size– Treats all precipitation as rain
![Page 24: Ewan OConnor, Robin Hogan, Anthony Illingworth Drizzle comparisons.](https://reader036.fdocuments.in/reader036/viewer/2022062619/5515f97e550346a2308b4896/html5/thumbnails/24.jpg)
Conclusion– Models have reasonable LWC
• Produce far too much drizzle• Precipitation reaches surface• Underestimate evaporation
– Met Office model• Overestimate of drizzle drop size