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Various types of models
have been used to examine the role of surface-induced circulations,
and to explore possible parameterization of these processes, since
these circulations
are typically smaller than the grid mesh used
in general circulation models (GCMs).
This includes an analytical model of a thermally-forced mesoscale motion,
developed by Dalu and Pielke [1993],
to suggest that fluxes by mesoscale motions can be as large
as fluxes by turbulent motions within the PBL.
The Colorado State University (CSU)
Regional Atmospheric Modeling System (RAMS) was used by
Avissar and Chen [1993] to simulate
mesocale circulations from a landscape discontinuity, and then
to examine its impact
on PBL structure and propose a parameterization scheme for
the resulting fluxes. Using the CSU
LES code, Hadfield et al. [1991] (and Walko et al. 1992)
examined the PBL turbulence field over
an imposed heat-flux variation (and imposed
terrain) in zero wind conditions. They observed induced
mean circulations that modulate the turbulent motions.
They also found that turbulence is consistently stronger
over the heat flux maxima (and over hilltops).
Hadfield et al. [1992] extended their LES study of no wind condition
to a light prevailing wind condition.
U.S. National Report to IUGG, 1991-1994
Rev. Geophys. Vol. 33
Suppl., © 1995 American Geophysical Union