High resolution COPE simulations
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Transcript of High resolution COPE simulations
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High resolution COPE simulationsKirsty Hanley, Humphrey Lean
MetOffice@Reading, UK
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UKV – 1.5km grid length, 70 levels, 2D subgrid turbulence scheme,BL mixing in vertical.
500m model – 500x400 km
200m model – 300x200 km
100m model – 150x100 km
High res models: 140 vertical levels, 3D subgrid turbulence scheme,RHcrit is 0.97 (0.91) in 1st few layers decreasing smoothly to 0.9 (0.8) at ~3.5km.
Set of nested models.
Model setup – UM vn8.2 PS32
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18 July – popcorn convection up to 9km
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3 Aug – convergence line
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15 Aug – intense warm rain showers
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25 July – line of showers up to 3km
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25 July – line of showers up to 3kmScale-aware microphysics package
Scheme includes new autoconversion, subgrid variability of cloud & rain, new drop-size distribution.
See Boutle et al 2014, MWR for more details.
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25 July – line of showers up to 3kmIan’s microphysics package
New package reduces precipitation but lines still break up in 200m and 100m simulations.
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Summary 1
• Saw quite high rainrates from warm rain.
• Cells appear to get smaller as grid length is reduced – this agrees with work done for DYMECS.
• The high resolution models produce too much rain.
• Lines appear to break up in 200m and 100m model – why?
• More cases can be seen in the report sent out last Friday.
• Are the cells getting smaller a result of the updrafts getting narrower or is it a microphysics issue? Look at a sea breeze case without precipitation to isolate
vertical velocity.
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July 5 – sea breeze convergence
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July 5 – sea breeze convergence
Different scale!
Vertical velocity at 500m amsl
Extended 200m and 100m domains by 50km to north
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July 5 – sea breeze convergence - Davidstow
Lidar data provided by Barbara Brooks
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July 5 – sea breeze convergence - Davidstow
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11 UTC
14 UTC
13 UTC
12 UTC
Angle of 135̊ from radar
UKV initially moves slower but then speeds up: Between 12-14UTC UKV moves ~10km, high res move ~7.5km
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Sea breeze moves ~8km in 1 hour.
Reflectivity Velocity
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July 5 – sea breeze convergence
More low cloud in UKV -> lower surface temperatures -> sea breeze convergence moves slower initially.
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July 5 – sea breeze convergence – FAAM obs
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July 5 – sea breeze convergence – FAAM obs
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July 5 – sea breeze convergence – surface obs
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Summary 2 and Future Work• Updraft magnitude and width compares reasonably well
between the observations and the high resolution models• How does cloud width compare?• What determines front propagation speed? Roll
spacing/depth?
• Why do high res models break up lines and produce too much precipitation?
• Compare simulations with other measurements – FAAM, King Air, Radar, Lidar, surface stations.
• Identify key areas of difference between models and observations:• Timing, location, size and intensity of cells.
• Cases of particular interest:• 5 July, 18 July, 25 July, 3 August, 15 August