© crown copyright met office high resolution cope simulations kirsty hanley, humphrey lean...
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© Crown copyright Met Office
High resolution COPE simulationsKirsty Hanley, Humphrey Lean
MetOffice@Reading, UK
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COPE• Field campaign to study the production of
precipitation in organised convective systems over SW England during July and August 2013
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Aims of COPE
• Understand the physical processes involved in convective precipitation.
• Improve the representation of microphysical processes in operational km-scale NWP.
• Improve the exploitation of data used for operational assimilation.
• Leading to improved forecast of convective precipitation that can cause flash flooding.
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COPE IOPs
Sea breeze
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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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25 July – line of showers up to 3km
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29 July – organised convective line over SW peninsula
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3 August – convergence line
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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 maybe produce too much rain.
• Lines appear to break up in 200m and 100m model – why?
• Are the cells getting smaller a result of the updrafts getting narrower or is it a micophysics 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
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July 5 – sea breeze convergence FAAM obs
Different colours are different times
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July 5 – sea breeze convergence
Vertical velocity at 325m 13Z
UKV 500m
100m200m
Different scale!
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July 5 – sea breeze convergence
Vertical velocity at 13Z
UKV
500m
100m
200m
1.5
6
6
6-2
-2
-2
-0.5
0
0
0
0
4
1
4
4
2
0.5
2
2
0
0
0
0
1000
1000
1000
1000
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Westerly wind at 13Z
UKV
500m
100m
200m
5
5
5-5
-5
-5
-5
0
0
0
0
5
July 5 – sea breeze convergence
1000
1000
1000
1000
0
0
0
0
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July 5 – sea breeze convergence
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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?
• Compare simulations with lidar and King Air measurements.
• Identify key areas of difference between models and observations:• Timing, location, size and intensity of cells.