Presentation on theme: "Convection Initiative discussion points What info do parametrizations & 1.5-km forecasts need? –Initiation mechanism, time-resolved cell size & updraft."— Presentation transcript:
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?
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!
1.Radar sees clear-air scattering boundary-layer top (Morcrette 2007) 2.Refractivity: moisture convergence 3.Doppler lidar: BL turbulence: Initiation, BL properties Radar BL top Mesoscale model BL top
1/4-degree beam provides very high resolution cloud structure compared to smaller (e.g. mobile) radars: Congestus Mature cells Dissipating cell 30 dBZ iso-surface (~precip) 5 dBZ iso-surface (~cloud) Cloud structure Derive dissipation rate from spectral width (Chapman & Browning 2001)
Vertical wind 1.Track features in horizontal velocity –Typical cell transported 50 25 Mt in 50-mins –Counter-gradient momentum flux in lower troposphere
Vertical wind cont. 2.Line convection: assume 2D flow and integrate continuity equation (Browning et al. 1997) Microphysics Polarimetric radar measurements –Variational retrieval (Hogan 2007)... Can also estimate ice water content. Rain rate Hail fraction