Study of a prototypical convective boundary layer observed during BLLAST: contributions by large-scale forcings

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Cita com:
hdl:2117/27590
Tipus de documentArticle
Data publicació2015-04-24
Condicions d'accésAccés obert
Abstract
We study the influence of the large-scale at-
mospheric contribution to the dynamics of the convective
boundary layer (CBL) in a situation observed during the
Boundary Layer Late Afternoon and Sunset Turbulence
(BLLAST) field campaign. We employ two modeling ap-
proaches, the mixed-layer theory and large-eddy simulation
(LES), with a complete data set of surface and upper-air at-
mospheric observations, to quantify the contributions of the
advection of heat and moisture, and subsidence. We find
that by only taking surface and entrainment fluxes into ac-
count, the boundary-layer height is overestimated by 70 %.
Constrained by surface and upper-air observations, we infer
the large-scale vertical motions and horizontal advection of
heat and moisture. Our findings show that subsidence has a
clear diurnal pattern. Supported by the presence of a nearby
mountain range, this pattern suggests that not only synoptic
scales exert their influence on the boundary layer, but also
mesoscale circulations. LES results show a satisfactory cor-
respondence of the vertical structure of turbulent variables
with observations. We also find that when large-scale ad-
vection and subsidence are included in the simulation, the
values for turbulent kinetic energy are lower than without
these large-scale forcings. We conclude that the prototypical
CBL is a valid representation of the boundary-layer dynam-
ics near regions characterized by complex topography and
small-scale surface heterogeneity, provided that surface- and
large-scale forcings are representative for the local boundary layer.
CitacióPietersen, H. [et al.]. Study of a prototypical convective boundary layer observed during BLLAST: contributions by large-scale forcings. "Atmospheric chemistry and physics", 24 Abril 2015, vol. 15, p. 4241-4257.
ISSN1680-7316
Versió de l'editorhttp://www.atmos-chem-phys.net/15/4241/2015/acp-15-4241-2015.html
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