© crown copyright met office high resolution cope simulations kirsty hanley, humphrey lean...

© Crown copyright Met Office

High resolution COPE simulationsKirsty Hanley, Humphrey Lean

MetOffice@Reading, UK


COPE• Field campaign to study the production of

precipitation in organised convective systems over SW England during July and August 2013


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.


COPE IOPs

Sea breeze


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


18 July – popcorn convection up to 9km


25 July – line of showers up to 3km


29 July – organised convective line over SW peninsula


3 August – convergence line


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.


July 5 – sea breeze convergence


July 5 – sea breeze convergence FAAM obs

Different colours are different times



Vertical velocity at 325m 13Z

UKV 500m

100m200m

Different scale!



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


Westerly wind at 13Z

UKV

500m

100m

200m

5

5

5-5

-5

-5

-5

0

0

0

0

5


1000

1000

1000

1000

0

0

0

0


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.

© crown copyright met office high resolution cope simulations kirsty hanley, humphrey lean...

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