lmd_Grandpeix2004.bib
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@article{2004QJRMS.130.3223T,
author = {{Tailleux}, R. and {Grandpeix}, J.~Y.},
title = {{On the seemingly incompatible parcel and globally integrated views of the energetics of triggered atmospheric deep convection over land}},
journal = {Quarterly Journal of the Royal Meteorological Society},
keywords = {CONVECTIVE AVAILABLE POTENTIAL ENERGY, CONVECTIVE INHIBITION ENERGY, ENERGY CYCLE, MULTIPLE REFERENCE STATES},
year = 2004,
month = oct,
volume = 130,
pages = {3223-3243},
abstract = {{The energetics of the diurnal cycle of atmospheric deep convection over
land remain difficult to understand and simulate accurately with current
cumulus parametrizations. Furthermore, a proper formulation has remained
elusive owing to seeming incompatibilities between, on the one hand, the
parcel view of energetics which relies on such concepts as Convective
Available Potential Energy (CAPE) and Convective Inhibition (CIN), and,
on the other hand, the globally integrated view, which relies on such
concepts as Moist Available Energy (MAE), reference states, and energy
conversion terms. While the MAE is intuitively the global counterpart of
the parcel-defined CAPE, there seems to be no global analogue to the
parcel-defined concept of energy barrier attached to CIN. To gain
insights into this issue, a new cost function PE is introduced to
quantify the amount of positive or negative energy required for a given
sounding to undergo an arbitrary adiabatic rearrangement of mass, and
which encompasses both the parcel-defined and global energy concepts as
particular cases. The function PE offers a complementary view of the
stability and energy characteristics of atmospheric soundings, whose
local minima are naturally associated with the reference states of the
system. It is established that: (a) MAE is essentially equivalent to
CAPE multiplied by a mass conversion factor Mb which scales as the
amount of convectively unstable boundary-layer air. Using the available
summer 1997 IOP data from the ARM- SGP site, Mb is found to correlate
with CAPE, which suggests the existence of a functional relationship
between CAPE and MAE; if further confirmed, this result would
considerably simplify the computation of MAE. (b) A global counterpart
to the parcel-defined concept of energy barrier can only be defined if
the system considered admits several reference states, and not one as is
classically assumed. In that case, energy barriers naturally arise as
the amount of energy required to switch from one reference state to
another. In the context of triggered deep convection, there must be at
least two reference states: a shallow one, which is the actual state (or
a slightly modified one if there is boundary layer CAPE), and a deep one
associated with the release of MAE/CAPE; the energy barrier separating
these two reference states naturally defines a generalized CIN. In the
limited context of the above-mentioned IOP ARM data, it is further shown
that: (c) Spatially averaged conditions exhibiting potential instability
to deep convection may be associated with individual soundings having
widely different stability characteristics, including absolute
stability, potential instability, and absolute instability; this
suggests that triggered deep convection may not necessarily be the
result of a parcel's vertical kinetic energy exceeding its negative
buoyancy, but rather from the destruction of convective inhibition (i.e.
production of absolute instability) in a local region. (d) A few local
soundings exhibit multiple reference states, corresponding roughly to
multiple levels of neutral buoyancy. These may allow for convective
clouds with cloud-top heights significantly lower than those classically
predicted by the undiluted ascent of a boundary-layer air parcel up to
its highest level of neutral buoyancy, even in the absence of complex
entrainment scenarios.
}},
doi = {10.1256/qj.03.140},
adsurl = {http://adsabs.harvard.edu/abs/2004QJRMS.130.3223T},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2004QJRMS.130.3207G,
author = {{Grandpeix}, J.~Y. and {Phillips}, V. and {Tailleux}, R.},
title = {{Improved mixing representation in Emanuel's convection scheme}},
journal = {Quarterly Journal of the Royal Meteorological Society},
keywords = {CUMULUS PARAMETRIZATION, ENTRAINMENT, MIXING, TROPOSPHERIC HUMIDITY},
year = 2004,
month = oct,
volume = 130,
pages = {3207-3222},
abstract = {{Recent empirical and modelling studies suggest that mid-tropospheric
relative humidity (RH) is an important controlling factor of deep
atmospheric convection, which appears to be underestimated in present
cumulus parametrizations. This indicates the possible presence of
shortcomings in the way that entrainment is represented in such
parametrizations. This matter was explored in the European Cloud Systems
project (EUROCS) by means of an idealized humidity experiment in which
the main controlling parameter is RH. In the latter study,
cloud-resolving model (CRM) experiments suggested that a shallow/deep
convection transition occurs when RH crosses a threshold value that
ranges from about RH = 50\% to RH = 60\%. In this paper, we seek to
increase the responsiveness of Emanuel's convection scheme to RH, and to
reproduce the threshold behaviour of the idealized humidity case, by
replacing the original uniform probability density function (PDF) for
mixing fractions by a more flexible two-parameter bell-shaped function
that allows a wider range of behaviour. The main result is that the
parameters of this PDF can be tuned to allow a regime transition to
occur near a threshold value of RH 55\%. In contrast to CRM results,
however, this transition is between two different regimes of deep
convection rather than between a shallow and deep regime. Possible ways
to obtain a shallow-to-deep transition with Emanuel's scheme are
discussed.
}},
doi = {10.1256/qj.03.144},
adsurl = {http://adsabs.harvard.edu/abs/2004QJRMS.130.3207G},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2004QJRMS.130.3055D,
author = {{Derbyshire}, S.~H. and {Beau}, I. and {Bechtold}, P. and {Grandpeix}, J.-Y. and
{Piriou}, J.-M. and {Redelsperger}, J.~L. and {Soares}, P.~M.~M.
},
title = {{Sensitivity of moist convection to environmental humidity}},
journal = {Quarterly Journal of the Royal Meteorological Society},
keywords = {CUMULUS CONVECTION, HUMIDITY SENSITIVITY, MODEL INTERCOMPARISON},
year = 2004,
month = oct,
volume = 130,
pages = {3055-3079},
abstract = {{As part of the EUROCS (EUROpean Cloud Systems study) project,
cloud-resolving model (CRM) simulations and parallel single-column model
(SCM) tests of the sensitivity of moist atmospheric convection to
mid-tropospheric humidity are presented. This sensitivity is broadly
supported by observations and some previous model studies, but is still
poorly quantified. Mixing between clouds and environment is a key
mechanism, central to many of the fundamental differences between
convection schemes. Here, we define an idealized quasi-steady 'testbed',
in which the large-scale environment is assumed to adjust the local mean
profiles on a timescale of one hour. We then test sensitivity to the
target profiles at heights above 2 km. Two independent CRMs agree
reasonably well in their response to the different background profiles
and both show strong deep precipitating convection in the more moist
cases, but only shallow convection in the driest case. The CRM results
also appear to be numerically robust. All the SCMs, most of which are
one-dimensional versions of global climate models (GCMs), show
sensitivity to humidity but differ in various ways from the CRMs. Some
of the SCMs are improved in the light of these comparisons, with GCM
improvements documented elsewhere.
}},
doi = {10.1256/qj.03.130},
adsurl = {http://adsabs.harvard.edu/abs/2004QJRMS.130.3055D},
adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
