[Tiimes-extended] [Fwd: Dynamics Happy Hour, Today, 3:30pm]

[Terri Cantrell]

-------- Original Message --------
Subject: 	Dynamics Happy Hour, Today, 3:30pm
Date: 	Tue, 03 Feb 2009 10:06:45 -0700
From: 	Arlene Laing <laing at ucar.edu>
To: 	Arlene Laing <laing at ucar.edu>,staff at mail.mmm.ucar.edu, 
visitor at mail.mmm.ucar.edu
CC: 	John Marsham <j.marsham at see.leeds.ac.uk>
References: 	<web-19571149 at mail.ucar.edu>



Hi folks,

Just a reminder!!

Dynamics Happy Hour returns Today, Tue, 3 Feb 2009 in 
FL3-2072
 
Come join John Marsham, visiting scientist, for a
discussion of convection (in the atmosphere, in a beer, 
...),
cool undercurrents (in the atmosphere, in a beer, ...), 
...
 
----------------------------------------

"Observations of stacked slantwise circulations above a
cool undercurrent in an elevated mesoscale convective 
system"
 
by John Marsham, University of Leeds and NCAS (UK)

Abstract
--------

In the UK deep convective storms usually originate from
boundary-layer air. However, in other regions elevated
convection is common, particularly during the night (for
example in the Great Plains of the USA). Despite this,
there are few detailed studies of elevated systems,
compared with surface-based squall lines.

Observations of a series of elevated mesoscale
convective systems (MCSs) from one day from the UK
Convective Storm Initiation Project will be presented.
A detailed case-study of one of the MCSs reveals the
evolution of stacked slantwise circulations associated
with the elevated convection - thus the system had two 
stacked
rear-inflows, with the lowermost corresponding to a
moderately strong rear-inflow jet. When the upright
convection weakened, vigorous slantwise motions
continued for some time, but their slope decreased from 
the
initial 1 in 4 to 1 in 9.

The rear-inflow jet did not penetrate the cool
undercurrent and reach the surface; instead beneath
where it impacted the undercurrent took on a bore-like
structure with cusped waves at its top and Kelvin 
Helmholtz
billows behind. The raised head of the undercurrent lifted
overlying air of high theta-e sufficiently to overcome
convective inhibition. Initial simulations using the
Unified Model show a system approximately corresponding
to the one observed, with a significant surface cold pool
outflow and a single rear-inflow, which did penetrate
the stable layer.
 
-------------------------------
For more information, contact George Bryan
(gbryan at ucar.edu) or Arlene Laing (laing at ucar.edu)



-- 
_________________________________________

Terri A. Cantrell
303-497-8281

http://www.tiimes.ucar.edu
Acting Administrator


NCAR
The Institute for Integrative & Multidisciplinary Earth Studies (TIIMES)
P.O. Box 3000
FL1-2024
Boulder, CO 80307-3000

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