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Modelling of deep convective clouds and orographic triggering of convection

Modelling of deep convective clouds and orographic triggering of convection during the COPS experiment. Ralph Burton, NCAS (Leeds) Alan Gadian, NCAS (Leeds) Victoria Smith, ICAS, (Leeds) Stephen Mobbs, NCAS (Leeds). Outline of talk. 1. 15 th July – deep convection.

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Modelling of deep convective clouds and orographic triggering of convection

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  1. Modelling of deep convective clouds and orographic triggering of convection during the COPS experiment Ralph Burton, NCAS (Leeds) Alan Gadian, NCAS (Leeds) Victoria Smith, ICAS, (Leeds) Stephen Mobbs, NCAS (Leeds) This is the footer

  2. Outline of talk. 1. 15th July – deep convection. 2. 12th August – outflows and convergence. 3. Summary. How well does WRF simulate these cases?

  3. 15th July: isolated deep convective cloud Note the location and orientation (SW-NEish) of the storm cloud From the Science Directory (Evelyne Richard) Summary

  4. 15th July: isolated deep convective cloud Observation of convective cloud, 15th July From the Science Directory (Evelyne Richard) Summary

  5. 15th July: isolated deep convective cloud? WRF convective cloud, 15th July

  6. WRF: inner domain: 700m resolution Outer domain 6.3km 1st nest 2.1km

  7. Sensitivity Tests

  8. WRF: sensitivity tests – CAPE and wind vectors: 15Z Ferrier; Betts-Miller

  9. WRF: skew-t and wind vectors: 15Z Isosurface of cloud water mixing ratio = 1E-4 kg/kg Cloud is quite shallow

  10. Comparison with observational data: AWS locations.

  11. Comparison with observational data: 2m temperatures. Black = obs.; red = WRF    temperature       time of day Many thanks to Simon Hölzl and Alex Göhm

  12. Comparison with observational data: 2m temperatures. Black = obs.; red = WRF 669m  1000m 1156m temperature 842m  962m 798m  507m  667m  928m time of day Many thanks to Simon Hölzl and Alex Göhm

  13. Comparison with observational data: 2m RH. Black = obs.; red = WRF 1156m 669m  relative humidity time of day Many thanks to Simon Hölzl and Alex Göhm

  14. Comparison with observational data: vertical profiles. OBS WRF

  15. Objective analysis: forcing the analysis with observations. OBSGRID – Objective analysis. Boundary layer RH, outer domain. 06Z, 15th July Achern and Hornisgrinde Radiosonde data With thanks to Cindy Bruyere, NCAR

  16. Orographic triggering: 12th August Case.

  17. Rain water, 2m temps., wind vectors. 1145Z 12th August

  18. Cloud, 2m temps., wind vectors. 1145Z 12th August

  19. Rain water, wind vectors, orogrpahy. 1300Z 12th August.

  20. 2m temps., wind vectors, orogrpahy. 1300Z 12th August. Note this cold area is over a roughly 2-D slope Relatively cool area

  21. Conclusions 15th July • Area of high(er) CAPE in the region of the “cloud” location. • Zone of convergence at the cloud location. BUT • Sensitivity to model Cu and microphysics • Other sensitivities… • GFS analysis appears to be too dry. • WRF does not seem to agree with obs. at higher elevations ( > ~ 850-900m) quite so well: under-predicts the 2m temp and over-predicts the RH: evaporative cooling? • ECMWF T799 analysis – ready to try! • Objective analysis

  22. 12th August • Outflow from clouds in model • Outflows appear to convergence, and cloud formed as a result • Good comparison with remote sensing data • Again, model agrees with obs. at lower elevations better than at higher elevations. • Need higher temporal resolution runs (output every minute) to isolate the mechanisms of triggering.

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