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RICO single column model simulations

RICO single column model simulations. Benjamin Devenish Met Office, UK. Outline of talk. Summary of model Sensitivity to vertical resolution Sensitivity to cloud microphysics parameterisations. Summary of model . Met Office GCM: Unified Model (UM) Turbulence mixing scheme

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RICO single column model simulations

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  1. RICO single column model simulations Benjamin Devenish Met Office, UK

  2. Outline of talk • Summary of model • Sensitivity to vertical resolution • Sensitivity to cloud microphysics parameterisations

  3. Summary of model • Met Office GCM: Unified Model (UM) • Turbulence mixing scheme • First-order closure • Non-local/explicit entrainment (Lock 2001) • Cumulus parameterisation • Based on Gregory and Rowntree (1990) mass flux scheme and Grant and Brown (1999) • Cloud fraction • Based on Smith (1990) • Cloud microphysics • Autoconversion based on Tripoli and Cotton (1980) • Assumed droplet number concentration

  4. Mass flux Detrainment begins at approximately 2000m Forced shallow convection No clear inversion Air parcel virtual potential temperature (dashed) vs ambient potential temperature (solid) adiabatic ascent No mid-level convection RICO simulations L38

  5. Large-scale cloud fraction L80 L38

  6. Convective cloud fraction L80 L38

  7. Mass flux L38 L80

  8. Surface fluxes Sensible heat flux Latent heat flux

  9. Average precipitation L38: 1.34 mm/day L80: 1.17 mm/day Total surface precipitation

  10. Precipitation (ctd) Large-scale precipitation Convective precipitation

  11. Potential temperature L38 L80

  12. Relative humidity L80 L38

  13. Zonal wind L80 L38

  14. Sensitivity to cloud microphysics • PC2 cloud scheme (UKMO) • Prognostic cloud and prognostic condensate (PC2) • Prognostic equations for vapour, liquid and ice contents and liquid, ice and total cloud fractions • Assess impact of each physical and dynamical process on clouds and condensate e.g. convection • KK autoconversion scheme • Based on Khairoutdinov and Kogan (2000) • Bulk microphysics parameterisation • Kessler-type parameterisation (liquid water partitioned into cloud water and drizzle)

  15. Total surface precipitation: PC2 + KK PC2 KK Average precipitation KK: 1.35 mm/day Average precipitation PC2: 1.68 mm/day All simulations L38 PC2 + KK Average precipitation PC2+KK: 1.47 mm/day

  16. Convective and large-scale precipitation KK PC2 PC2 + KK Conv. LS

  17. Cloud cover PC2 + KK PC2 Large-scale cloud only KK large-scale KK convective

  18. Conclusions • Difficulty in diagnosing shallow convection • Fairly insensitive to model resolution • Sensitivity to cloud microphysics • PC2 scheme rains too much

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