lmd_Hourdin2003.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,
month = dec,
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{2003Icar..166..328L,
author = {{Luz}, D. and {Hourdin}, F.},
title = {{Latitudinal transport by barotropic waves in Titan's stratosphere.. I. General properties from a horizontal shallow-water model}},
journal = {\icarus},
keywords = {Titan, dynamics, composition},
year = 2003,
month = dec,
volume = 166,
pages = {328-342},
abstract = {{We present a numerical study of barotropic waves in Titan's stratosphere
based on a shallow-water model. The forcing of the zonal flow by the
mean meridional circulation is represented by a relaxation towards a
barotropically unstable wind profile. The relaxation profile is
consistent with observations and with previous results from a 3D general
circulation model. The time constant of the forcing that best matches
the northward eddy-transport of zonal momentum from the 3D model is
{$\tau$}{\tilde}5 Titan days. The eddy wind field is a zonal wavenumber-2
wave with a peak amplitude about 10\% of the mean wind speed. The
latitudinal transport of angular momentum by the wave tends to keep the
flow close to marginal stability by carrying momentum upgradient, from
the core of the jets into the low latitudes. Although the strongest eddy
motions occur at the latitudes of the wind maxima, the strongest mixing
takes place at the barotropically unstable regions, close to
{\plusmn}30{\deg} and spanning about 30{\deg} in latitude. An eddy-mixing
time constant of the order of 1 Titan day is inferred within these
regions, and of a few tens of days within regions of stable flow.
Horizontal gradients in transient tracer fields are less than 10\% of the
latitudinal gradient of the meridional tracer profile. Cassini's
detection of such waves could provide a direct observation of wind
speeds at stratospheric levels.
}},
doi = {10.1016/j.icarus.2003.08.015},
adsurl = {http://adsabs.harvard.edu/abs/2003Icar..166..328L},
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,
month = may,
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}
}
