[GTP] GTP MMM Seminar at NCAR

[Silvia Gentile]

Joint GTP MMM Seminar
Land-surface Response to Shallow Cumulus
Fabienne Lohou
Laboratoire d'Aérologie, Toulouse, France
In collaboration with E. Patton, NCAR
Cloud feedbacks in the climate system are a major source of uncertainty 
in model projections of global warming. Analysis of satellite data and 
climate models suggests that much of this uncertainty is associated with 
low clouds. Due to their relatively small size and radiative impact, and 
their tendency not to produce rain, shallow cumulus clouds have received 
much less attention than the other cloud forms (\i.e. stratocumulus, 
deep precipitating convection, etc). A significant portion of the 
research has focused on understanding and parameterizing the transport 
and mixing associated with shallow cumulus and their roots within the 
subcloud layer. However, even though the impact of cumulus convection on 
surface fluxes has been shown to significantly affect larger-scale 
circulations and the skill of medium-range weather forecasts, the 
coupling between shallow cumulus and the land surface has received very 
little attention.
Passing shallow cumulus clouds briefly and intermittently reduces the 
surface solar irradiance. The surface responds by adjusting the balance 
between sensible, latent and soil heat flux. Precisely how the surface 
partitions the available energy among these fluxes and how boundary 
layer motions respond to these brief periods of cloud shading remains 
unclear. To analyze these relationships, we use a cloud-permitting 
version of NCAR’s Large Eddy Simulation code coupled with the NOAH Land 
Surface Model. Using initial conditions and forcing from a case during 
the Southern Great Plains 1997 study, we investigate the following 
questions surrounding the coupling between shallow cumulus and the land 
surface: To what magnitude do shallow cumulus clouds affect the surface 
energy balance on average? How does the surface react to sudden and 
local net radiation variations? How do shallow clouds affect the 
entrainment rate? How do shallow cumulus clouds impact surface 
measurement interpretation?

Friday August 26, 2011
Lecture: 10:30am (Coffee at 10:15)
Foothills Laboratory 2, Room 1001
This seminar will be webcasted and recorded
http://www.fin.ucar.edu/it/mms/fl-live.htm

-- 
Silvia Gentile
NCAR IMAGe
1850 Table Mesa Drive
Boulder, CO 803035
www2.image.ucar.edu/IMAGe