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High resolution COPE simulations

High resolution COPE simulations. Kirsty Hanley, Humphrey Lean MetOffice@Reading, UK. Model setup – UM vn8.2 PS32. 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

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High resolution COPE simulations

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  1. High resolution COPE simulations Kirsty Hanley, Humphrey Lean MetOffice@Reading, UK

  2. Model setup – UM vn8.2 PS32 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.

  3. 18 July – popcorn convection up to 9km

  4. 15 Aug – intense warm rain showers

  5. 25 July – line of showers up to 3km

  6. 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.

  7. 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.

  8. 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.

  9. July 5 – sea breeze convergence

  10. July 5 – sea breeze convergence Vertical velocity at 500m amsl Different scale! Extended 200m and 100m domains by 50km to north

  11. July 5 – sea breeze convergence – FAAM obs

  12. July 5 – sea breeze convergence – FAAM obs

  13. July 5 – sea breeze convergence - Davidstow Lidar data provided by Barbara Brooks

  14. July 5 – sea breeze convergence - Davidstow

  15. 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? • Working with Lindsay, Phil and John N on this case. • 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

  16. July 5 – sea breeze convergence More low cloud in UKV -> lower surface temperatures -> sea breeze convergence moves slower.

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