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Convection Initiative discussion points

Convection Initiative discussion points. What info do parametrizations & 1.5-km forecasts need? Initiation mechanism, time-resolved cell size & updraft velocity, entrainment rate, rain & hail rate, organization mechanisms? What are the priorities for an observational campaign?

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Convection Initiative discussion points

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  1. Convection Initiative discussion points • What info do parametrizations & 1.5-km forecasts need? • Initiation mechanism, time-resolved cell size & updraft velocity, entrainment rate, rain & hail rate, organization mechanisms? • What are the priorities for an observational campaign? • What was not learned from CSIP? Chilbolton or elsewhere? Focus on initiation or subsequent evolution? Aircraft sampling? Scan strategy? • What are the promising new ideas in parametrization? • Why is it so difficult? Is UK a suitable place to test parametrizations? How can we use high-res models to develop parametrizations? Can we inter-compare new approaches at University & Met Office • What are the priorities for flood forecasting? • How well are mechanisms for quasi-stationarity captured? Relative importance of back-building/orographic triggering/dynamical forcing? • What new datasets should be assimilated? New DA methods? • How important is microphysics, e.g. graupel & aerosol effects? • Where do we go from here? • Scope? Funding mechanism, e.g. consortium bid? External collaboration, e.g. Leeds? Timing? Leadership of project?

  2. Running order • Robin Hogan • Humphrey Lean • Ross Bannister / Stefano Migliorini • Dan Kirshbaum • Alan Grant • Bob Plant • Remi Tailleux To leave time for discussion afterwards, please aim for 7 mins + 2 mins for questions!

  3. Initiation, BL properties Radar BL top • Radar sees clear-air scattering boundary-layer top (Morcrette 2007) • Refractivity: moisture convergence • Doppler lidar: BL turbulence: Mesoscale model BL top

  4. Cloud structure Dissipating cell • 1/4-degree beam provides very high resolution cloud structure compared to smaller (e.g. mobile) radars: Mature cells Congestus 30 dBZ iso-surface (~precip) 5 dBZ iso-surface (~cloud) Derive dissipation rate from spectral width (Chapman & Browning 2001)

  5. Vertical wind • Track features in horizontal velocity • Typical cell transported 5025 Mt in 50-mins • Counter-gradient momentum flux in lower troposphere

  6. Vertical wind cont. 2. Line convection: assume 2D flow and integrate continuity equation (Browning et al. 1997) • Polarimetric radar measurements • Variational retrieval (Hogan 2007)... • Can also estimate ice water content. Rain rate Hail fraction Microphysics

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