Convection plans
Alison Stirling
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Priorities for convection
parametrization
Main Systematic Errors:
Diurnal cycle
MJO
Monsoons
AEW coupling
Feedback with
`large-scale’
environment
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Transient response
to boundary layer
Interaction with large scale
Ascent generates CAPE
Heating generates ascent
Depth and amplitude of convective response key to
improving monsoon, MJO, AEW coupling
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Interaction with large scale
progress and further work:
Increased entrainment improves
coupling between convection and
large-scale (Klingaman et al 2013)
Introduce physically realistic
entrainment dependence:
(stability and cloud area)
…but it can’t be
high all the time…
Explore effects of
large scale on other
parts of scheme
UM high resolution convection simulations over a large
domain allows circulations resulting from convection to
develop.
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Interaction with boundary layer
Introduce energetics of boundary layer thermals
Modify triggering and closure to have dependence on this
Cold pools
Important for:
1. Triggering and closure
Additional KE to overcome CIN
Temperature and moisture differences
allow CAPE to be present locally even
when the mean state is stable
Enhanced lifting
2. Entrainment
affects cloud area
(and therefore buoyancy
and vertical velocity)
Two zones of temperature and moisture
Requires memory of previous precipitation events
MOAP secondment to work on cold pools
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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?
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Convection position available!
Higher
resolutions
See
www.metoffice.gov.uk/about-us/jobs/
Closing date: 14th July 2013
• 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.
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Questions and answers
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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
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Unification details
Research areas include:
•Cloud area representation
•Cold pool representation
•Boundary layer thermal energetics
•Convective response to large-scale ascent
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UM run
Stu Webster
•
•
•
•
Indian Ocean
200m from 2.2km b.c.s
4000 x 2600 points
3 days
• http://www-hc/~hadsw/dkrf/gifs/dkrfw.10000.full.gif
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What controls convective
depth?
• Vertical extent of CAPE
• Entrainment
• Detrainment
High entrainment
increases coupling to
LS ascent/ descent,
but it can’t be high all
the time!
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Cloud area?
Boundary layer
processes? (e.g.
cold pools)
What controls heating
amplitude?
• Closure
Rate of CAPE
creation?
Inversion
removal?
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Ascent?