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© Crown copyright Met Office Convection plans Alison Stirling.

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Presentation on theme: "© Crown copyright Met Office Convection plans Alison Stirling."— Presentation transcript:

1 © Crown copyright Met Office Convection plans Alison Stirling

2 © Crown copyright Met Office Priorities for convection parametrization Main Systematic Errors: Diurnal cycle MJO Monsoons AEW coupling Feedback with `large-scale environment Transient response to boundary layer

3 © Crown copyright Met Office Interaction with large scale Ascent generates CAPE Heating generates ascent Depth and amplitude of convective response key to improving monsoon, MJO, AEW coupling

4 © Crown copyright Met Office Interaction with large scale progress and further work: UM high resolution convection simulations over a large domain allows circulations resulting from convection to develop. Increased entrainment improves coupling between convection and large-scale (Klingaman et al 2013) …but it cant be high all the time… Introduce physically realistic entrainment dependence: (stability and cloud area) Explore effects of large scale on other parts of scheme

5 © Crown copyright Met Office Interaction with boundary layer Cold pools Important for: 1. Triggering and closure Temperature and moisture differences allow CAPE to be present locally even when the mean state is stable Additional KE to overcome CIN 2. Entrainment affects cloud area (and therefore buoyancy and vertical velocity) Enhanced lifting Two zones of temperature and moisture Requires memory of previous precipitation events Introduce energetics of boundary layer thermals Modify triggering and closure to have dependence on this MOAP secondment to work on cold pools

6 © Crown copyright Met Office Research areas 1. Entrainment / detrainment Dependence on cloud area Dependence on stability Adaptivity 2. Interaction with large scale What is the profile of ascent caused by convective heating? How does ascent affect closure and at what levels is it important? 3. Interaction with boundary layer Representing energetic response to CIN Representing cold pools 4. Memory Relative importance of cloud area, rh variability, BL variability Prognostic for cloud area 5. Closure How do surface processes and upper level processes combine?

7 © Crown copyright Met Office Higher resolutions Mass flux: Separate into component parts vertical velocity, cloud area, and cloud number Multiple plume: Quantify the need for a multi-plume approach Allows: grid-size sensitivity, inclusion of microphysics better coupling with PC2 stochasticity Applications submitted for Reading and Leeds CASE students to work on different aspects of grey-zone problem. Convection position available! See Closing date: 14 th July 2013

8 © Crown copyright Met Office Questions and answers

9 © Crown copyright Met Office Unification Give each component of the existing convection scheme an improved physical basis. Entrainment: Include dependence on stability and cloud area Detrainment: Reformulate to be adaptive all the way up the cloud, and let the level of adaptivity depend on cloud area Triggering and closure: Base on energetics of boundary layer processes and large-scale ascent

10 © Crown copyright Met Office Unification details Research areas include: Cloud area representation Cold pool representation Boundary layer thermal energetics Convective response to large-scale ascent

11 © Crown copyright Met Office UM run Stu Webster Indian Ocean 200m from 2.2km b.c.s 4000 x 2600 points 3 days

12 © Crown copyright Met Office What controls convective depth? Vertical extent of CAPE Entrainment Detrainment Cloud area? Boundary layer processes? (e.g. cold pools) High entrainment increases coupling to LS ascent/ descent, but it cant be high all the time!

13 © Crown copyright Met Office What controls heating amplitude? Closure Rate of CAPE creation? Inversion removal? Ascent?


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