High resolution COPE simulations Kirsty Hanley Humphrey Lean

High resolution COPE simulations Kirsty Hanley, Humphrey Lean Met. Office@Reading, UK © Crown copyright Met Office

Model setup – UM vn 8. 2 PS 32 Set of nested models. UKV – 1. 5 km grid length, 70 levels, 2 D subgrid turbulence scheme, BL mixing in vertical. 500 m model – 500 x 400 km 200 m model – 300 x 200 km 100 m model – 150 x 100 km High res models: 140 vertical levels, 3 D subgrid turbulence scheme, RHcrit is 0. 97 (0. 91) in 1 st few layers decreasing smoothly to 0. 9 (0. 8) at ~3. 5 km. © Crown copyright Met Office

18 July – popcorn convection up to 9 km © Crown copyright Met Office

3 Aug – convergence line © Crown copyright Met Office

15 Aug – intense warm rain showers © Crown copyright Met Office

25 July – line of showers up to 3 km © Crown copyright Met Office

25 July – line of showers up to 3 km Scale-aware microphysics package Scheme includes new autoconversion, subgrid variability of cloud & rain, new dropsize distribution. See Boutle et al 2014, MWR for more details. © Crown copyright Met Office

25 July – line of showers up to 3 km Ian’s microphysics package New package reduces precipitation but lines still break up in 200 m and 100 m simulations. © Crown copyright Met Office

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 200 m and 100 m 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? Ø Look at a sea breeze case without precipitation to isolate vertical velocity. © Crown copyright Met Office

July 5 – sea breeze convergence © Crown copyright Met Office

July 5 – sea breeze convergence Vertical velocity at 500 m amsl Different scale! Extended 200 m and 100 m domains by 50 km to north © Crown copyright Met Office

July 5 – sea breeze convergence - Davidstow © Crown copyright Met Office Lidar data provided by Barbara Brooks

July 5 – sea breeze convergence - Davidstow © Crown copyright Met Office

11 UTC 12 UTC Angle of 135 from radar UKV initially moves slower but then 13 UTC speeds up: Between 12 -14 UTC UKV moves ~10 km, high res move ~7. 5 km 14 UTC © Crown copyright Met Office

Reflectivity Sea breeze moves ~8 km in 1 hour. © Crown copyright Met Office Velocity

July 5 – sea breeze convergence More low cloud in UKV -> lower surface temperatures > sea breeze convergence moves slower initially. © Crown copyright Met Office

July 5 – sea breeze convergence – FAAM obs © Crown copyright Met Office

July 5 – sea breeze convergence – FAAM obs © Crown copyright Met Office

July 5 – sea breeze convergence – surface obs © Crown copyright Met Office

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 © Crown copyright Met Office