high resolution cope simulations

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High resolution COPE simulationsKirsty Hanley, Humphrey Lean

MetOffice@Reading, UK


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


3 Aug – convergence line


15 Aug – intense warm rain showers


25 July – line of showers up to 3km


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.


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.


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.


July 5 – sea breeze convergence



Different scale!

Vertical velocity at 500m amsl

Extended 200m and 100m domains by 50km to north


July 5 – sea breeze convergence - Davidstow

Lidar data provided by Barbara Brooks


July 5 – sea breeze convergence - Davidstow


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


Sea breeze moves ~8km in 1 hour.

Reflectivity Velocity



More low cloud in UKV -> lower surface temperatures -> sea breeze convergence moves slower initially.


July 5 – sea breeze convergence – FAAM obs


July 5 – sea breeze convergence – surface obs


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

high resolution cope simulations

Documents