pub2003.bib

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@article{2003Icar..166..343L,
  author = {{Luz}, D. and {Hourdin}, F. and {Rannou}, P. and {Lebonnois}, S.
	},
  title = {{Latitudinal transport by barotropic waves in Titan's stratosphere.. II. Results from a coupled dynamics-microphysics-photochemistry GCM}},
  journal = {\icarus},
  year = 2003,
  volume = 166,
  pages = {343-358},
  abstract = {{We present a 2D general circulation model of Titan's atmosphere,
coupling axisymmetric dynamics with haze microphysics, a simplified
photochemistry and eddy mixing. We develop a parameterization of
latitudinal eddy mixing by barotropic waves based on a shallow-water,
longitude-latitude model. The parameterization acts locally and in real
time both on passive tracers and momentum. The mixing coefficient varies
exponentially with a measure of the barotropic instability of the mean
zonal flow. The coupled GCM approximately reproduces the Voyager
temperature measurements and the latitudinal contrasts in the
distributions of HCN and C $_{2}$H $_{2}$, as well as the
main features of the zonal wind retrieved from the 1989 stellar
occultation. Wind velocities are consistent with the observed reversal
time of the North-South albedo asymmetry of 5 terrestrial years. Model
results support the hypothesis of a non-uniform distribution of infrared
opacity as the cause of the Voyager temperature asymmetry. Transport by
the mean meridional circulation, combined with polar vortex isolation
may be at the origin of the latitudinal contrasts of trace species, with
eddy mixing remaining restricted to low latitudes most of the Titan
year. We interpret the contrasts as a signature of non-axisymmetric
motions.
}},
  doi = {10.1016/j.icarus.2003.08.014},
  adsurl = {http://adsabs.harvard.edu/abs/2003Icar..166..343L},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2003PhFl...15.2791M,
  author = {{Millour}, E. and {Labrosse}, G. and {Tric}, E.},
  title = {{Sensitivity of binary liquid thermal convection to confinement}},
  journal = {Physics of Fluids},
  keywords = {Chaos in fluid dynamics, Slip flows and accommodation, Nonlinearity bifurcation and symmetry breaking, Particle-laden flows, Flows in ducts channels nozzles and conduits},
  year = 2003,
  volume = 15,
  pages = {2791-2802},
  abstract = {{The stable axisymmetric convective states of a binary liquid enclosed in
a vertical cylinder heated from below are exhaustively and accurately
identified by pseudo-spectral numerical integration. In order to gain
some insight on the influence that nearby boundaries can exert on flow
dynamics, three aspect ratios (1/2, 1, and 2), as well as two types of
lateral kinematic boundary conditions (either no-slip or free-slip) are
investigated. The ranges over which stable quiescent, oscillatory and
steady convective states extend and coexist are given. The bifurcations
leading to transitions from one branch of solutions to another, as well
as those that occur along the oscillatory branch, are analyzed. The most
significant effect of varying boundary conditions and aspect ratio
involves the route from oscillatory to steady convection. For a given
configuration, that route consists of a period doubling cascade followed
by chaos, or a subcritical generalized Hopf (or Neimark-Sacker)
bifurcation, or a homoclinic bifurcation. The dynamics of thermal
convection of enclosed binary mixtures is clearly very sensitive to both
boundary conditions and aspect ratio.
}},
  doi = {10.1063/1.1600439},
  adsurl = {http://adsabs.harvard.edu/abs/2003PhFl...15.2791M},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2003Icar..164...33T,
  author = {{Tobie}, G. and {Forget}, F. and {Lott}, F.},
  title = {{Numerical simulation of the winter polar wave clouds observed by Mars Global Surveyor Mars Orbiter Laser Altimeter}},
  journal = {\icarus},
  year = 2003,
  volume = 164,
  pages = {33-49},
  abstract = {{In 1998, the Mars Orbiter Laser Altimeter revealed the presence of
isolated or quasi-periodic thick clouds during the martian polar night.
They are believed to be composed of CO $_{2}$ ice particles and to
be tilted against the wind direction, a feature characteristic of
vertically propagating orographic gravity waves. To support that
interpretation, we present here numerical simulations with a
two-dimensional anelastic model of stratified shear flow that includes
simple CO $_{2}$ ice microphysics. In some of the simulations
presented, the orography is an idealized trough, with dimensions
characteristic of the many troughs that shape the Mars polar cap. In
others, it is near the real orography. In the polar night conditions,
our model shows that gravity waves over the north polar cap are strong
enough to induce adiabatic cooling below the CO $_{2}$ frost
point. From this cooling, airborne heterogeneous nucleation of CO
$_{2}$ ice particles occurs from the ground up to the altitude of
the polar thermal inversion. Although the model predicts that clouds can
be present above 15 km, only low altitude clouds can backscatter the
Laser beams of MOLA at a detectable level. Accordingly, the shape of the
Laser echoes is related to the shape of the clouds at low level, but do
not necessarily coincide with the top of the clouds. The model helps to
interpret the cloud patterns observed by MOLA. Above an isolated
orographic trough, an isolated extended sloping cloud tilted against the
wind is obtained. The model shows that the observed quasi-periodic
clouds are due to the succession of small-scale topographic features,
rather than to the presence of resonant trapped lee waves. Indeed, the
CO $_{2}$ condensation greatly damps the buoyancy force, essential
for the maintenance of gravity waves far from their sources. Simulations
with realistic topography profiles show the cloud response is sensitive
to the wind direction. When the wind is directed upslope of the polar
cap, on the one hand, a large scale cloud, modulated by small-scale
waves, forms just above the ground. On the other hand, when the wind is
directed downslope, air is globally warmed, and periodic ice clouds
induced by small-scale orography form at altitudes higher than 3-5 km
above the ground. In both cases, a good agreement between the simulated
echoes and the observed one is obtained. According to our model, we
conclude that the observed clouds are quasi-stationary clouds made of
moving ice particles that successively grow and sublimate by crossing
cold and warm phases of orographic gravity waves generated by the
successive polar troughs. We also find that the rate of ice
precipitation is relatively weak, except when there is a large scale air
dynamical cooling.
}},
  doi = {10.1016/S0019-1035(03)00131-3},
  adsurl = {http://adsabs.harvard.edu/abs/2003Icar..164...33T},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2003Icar..163..164L,
  author = {{Lebonnois}, S. and {Hourdin}, F. and {Rannou}, P. and {Luz}, D. and 
	{Toublanc}, D.},
  title = {{Impact of the seasonal variations of composition on the temperature field of Titan's stratosphere}},
  journal = {\icarus},
  year = 2003,
  volume = 163,
  pages = {164-174},
  abstract = {{We investigate the role of seasonal variations of Titan's stratospheric
composition on the temperature. We use a general circulation model
coupled with idealized chemical tracers that reproduce variations of
ethane (C $_{2}$H $_{6}$), acetylene (C $_{2}$H
$_{2}$), and hydrogen cyanide (HCN). Enhancement of the mole
fractions of these compounds, at high latitudes in the winter hemisphere
relative to their equatorial values, induces a relative decrease in
temperature above approximately 0.2 mbar, with a peak amplitude around
-20 K, and a relative increase in temperature below, around 1 mbar, with
a peak amplitude around +7 K. These thermal effects are mainly due to
the variations of the cooling to space induced by the varying
distributions. The ethane, acetylene, and hydrogen cyanide variations
affect the cooling rates in a similar way, with the dominant effect
being due to ethane, though its latitudinal variations are small.
}},
  doi = {10.1016/S0019-1035(03)00074-5},
  adsurl = {http://adsabs.harvard.edu/abs/2003Icar..163..164L},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2003JGRE..108.5027M,
  author = {{Mangold}, N. and {Costard}, F. and {Forget}, F.},
  title = {{Debris flows over sand dunes on Mars: Evidence for liquid water}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Planetology: Solar System Objects: Mars, Planetology: Solar System Objects: Comparative planetology, Hydrology: Geomorphology (1625), Hydrology: Frozen ground, Planetary Sciences: Surface materials and properties,},
  year = 2003,
  volume = 108,
  eid = {5027},
  pages = {8-1},
  abstract = {{This study focuses on the formation and physical properties of the
gullies observed over large Martian dunes, especially those of the
Russell crater (54{\deg}S, 347{\deg}W). Geomorphic features like
sinuosities and connections of the channels show that gullies over dunes
involve flows with a significant proportion of liquid. The occurrence of
levees implies that these flows are debris flows with a yield strength
characteristics of Bingham plastic materials. We apply terrestrial
methods to estimate viscosity and velocity of these flows from levee
size and sinuosities. We obtain average velocities in the range of 1 to
7 m s$^{-1}$ and apparent viscosities of 2.8 to 46,000 Pa s, with
an average at 740 Pa s, compared with the 0.001 Pa s of pure water.
These viscosities and velocities are in the range of terrestrial debris
flows with a proportion of 10 to 40\% of H$_{2}$O. These properties
are typical of water-holding debris flows but not of pure water surface
runoff or CO$_{2}$ driven flows. The debris flows over dunes are
oriented on south-facing slopes like other recent gullies. Meltwater
from ground ice formed during a recent period of high obliquity is the
more likely explanation for the formation of such flows over dunes.
}},
  doi = {10.1029/2002JE001958},
  adsurl = {http://adsabs.harvard.edu/abs/2003JGRE..108.5027M},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2003Icar..161..474L,
  author = {{Lebonnois}, S.~é. and {Bakes}, E.~L.~O. and {McKay}, C.~P.
	},
  title = {{Atomic and molecular hydrogen budget in Titan's atmosphere}},
  journal = {\icarus},
  year = 2003,
  volume = 161,
  pages = {474-485},
  abstract = {{Using a one-dimensional model, we investigate the hydrogen budget and
escape to space in Titan's atmosphere. Our goal is to study in detail
the distributions and fluxes of atomic and molecular hydrogen in the
model, while identifying sources of qualitative and quantitative
uncertainties. Our study confirms that the escape of atomic and
molecular hydrogen to space is limited by the diffusion through the
homopause level. The H distribution and flux inside the atmosphere are
very sensitive to the eddy diffusion coefficient used above altitude 600
km. We chose a high value of this coefficient 1 {\times} 10 $^{8}$
cm $^{2}$ s $^{-1}$ and a homopause level around altitude
900 km. We find that H flows down significantly from the production
region above 500 km to the region [300-500] km, where it recombines into
H $_{2}$. Production of both H and H $_{2}$ also occurs in
the stratosphere, mostly from photodissociation of acetylene. The only
available observational data to be compared are the escape rate of H
deduced from Pioneer 11 and IUE observations of the H torus 1-3 {\times}
10 $^{9}$ cm $^{-2}$ s $^{-1}$ and the latest
retrieved value of the H $_{2}$ mole fraction in the stratosphere:
(1.1 {\plusmn} 0.1) {\times} 10 $^{-3}$. Our results for both of
these values are at least 50-100\% higher, though the uncertainties
within the chemical schemes and other aspects of the model are large.
The chemical conversion from H to H $_{2}$ is essentially done
through catalytic cycles using acetylene and diacetylene. We have
studied the role of this diacetylene cycle, for which the associated
reaction rates are poorly known. We find that it mostly affects C
$_{4}$ species and benzene in the lower atmosphere, rather than
the H profile and the hydrogen budget. We have introduced the
heterogenous recombination of hydrogen on the surface of aerosol
particles in the stratosphere, and this appears to be a significant
process, comparable to the chemical processes. It has a major influence
on the H distribution, and consequently on several other species,
especially C $_{3}$H $_{4}$, C $_{4}$H $_{2}$
and C $_{6}$H $_{6}$. Therefore, this heterogenous process
should be taken into account when trying to understand the stratospheric
distribution of these hydrocarbons.
}},
  doi = {10.1016/S0019-1035(02)00039-8},
  adsurl = {http://adsabs.harvard.edu/abs/2003Icar..161..474L},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}
@article{2003Icar..161..468B,
  author = {{Bakes}, E.~L.~O. and {Lebonnois}, S.~é. and {Bauschlicher}, C.~W. and 
	{McKay}, C.~P.},
  title = {{The role of submicrometer aerosols and macromolecules in H $_{2}$ formation in the titan haze}},
  journal = {\icarus},
  year = 2003,
  volume = 161,
  pages = {468-473},
  abstract = {{Previous studies of the photochemistry of small molecules in Titan's
atmosphere found it difficult to have hydrogen atoms removed at a rate
sufficient to explain the observed abundance of unsaturated
hydrocarbons. One qualitative explanation of the discrepancy nominated
catalytic aerosol surface chemistry as an efficient sink of hydrogen
atoms, although no quantitative study of this mechanism was attempted.
In this paper, we quantify how haze aerosols and macromolecules may
efficiently catalyze the formation of hydrogen atoms into H
$_{2}$. We describe the prompt reaction model for the formation of
H $_{2}$ on aerosol surfaces and compare this with the catalytic
formation of H $_{2}$ using negatively charged hydrogenated
aromatic macromolecules. We conclude that the PRM is an efficient
mechanism for the removal of hydrogen atoms from the atmosphere to form
H $_{2}$ with a peak formation rate of {\tilde} 70 cm $^{-3}$
s $^{-1}$ at 420 km. We also conclude that catalytic H
$_{2}$ formation via hydrogenated anionic macromolecules is viable
but much less productive (a maximum of {\tilde} 0.1 cm $^{-3}$ s
$^{-1}$ at 210 km) than microphysical aerosols.
}},
  doi = {10.1016/S0019-1035(02)00040-4},
  adsurl = {http://adsabs.harvard.edu/abs/2003Icar..161..468B},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}