@comment{{This file has been generated by bib2bib 1.97}}
@comment{{Command line: bib2bib --quiet -c year=2008 -c $type="ARTICLE" -oc pub2008.txt -ob pub2008.bib}}
  author = {{Crespin}, A. and {Lebonnois}, S. and {Vinatier}, S. and {Bézard}, B. and 
	{Coustenis}, A. and {Teanby}, N.~A. and {Achterberg}, R.~K. and 
	{Rannou}, P. and {Hourdin}, F.},
  title = {{Diagnostics of Titan's stratospheric dynamics using Cassini/CIRS data and the 2-dimensional IPSL circulation model}},
  journal = {\icarus},
  year = 2008,
  volume = 197,
  pages = {556-571},
  abstract = {{The dynamics of Titan's stratosphere is discussed in this study, based
on a comparison between observations by the CIRS instrument on board the
Cassini spacecraft, and results of the 2-dimensional circulation model
developed at the Institute Pierre-Simon Laplace, available at [Rannou, P., Lebonnois, S.,
Hourdin, F., Luz, D., 2005. Adv. Space Res. 36, 2194-2198]. The
comparison aims at both evaluating the model's capabilities and
interpreting the observations concerning: (1) dynamical and thermal
structure using temperature retrievals from Cassini/CIRS and the
vertical profile of zonal wind at the Huygens landing site obtained by
Huygens/DWE; and (2) vertical and latitudinal profiles of stratospheric
gases deduced from Cassini/CIRS data. The modeled thermal structure is
similar to that inferred from observations (Cassini/CIRS and Earth-based
observations). However, the upper stratosphere (above 0.05 mbar) is
systematically too hot in the 2D-CM, and therefore the stratopause
region is not well represented. This bias may be related to the haze
structure and to misrepresented radiative effects in this region, such
as the cooling effect of hydrogen cyanide (HCN). The 2D-CM produces a
strong atmospheric superrotation, with zonal winds reaching 200 m s
$^{-1}$ at high winter latitudes between 200 and 300 km altitude
(0.1-1 mbar). The modeled zonal winds are in good agreement with
retrieved wind fields from occultation observations, Cassini/CIRS and
Huygens/DWE. Changes to the thermal structure are coupled to changes in
the meridional circulation and polar vortex extension, and therefore
affect chemical distributions, especially in winter polar regions. When
a higher altitude haze production source is used, the resulting modeled
meridional circulation is weaker and the vertical and horizontal mixing
due to the polar vortex is less extended in latitude. There is an
overall good agreement between modeled chemical distributions and
observations in equatorial regions. The difference in observed vertical
gradients of C $_{2}$H $_{2}$ and HCN may be an indicator of
the relative strength of circulation and chemical loss of HCN. The
negative vertical gradient of ethylene in the low stratosphere at
15{\deg} S, cannot be modeled with simple 1-dimensional models, where a
strong photochemical sink in the middle stratosphere would be necessary.
It is explained here by dynamical advection from the winter pole towards
the equator in the low stratosphere and by the fact that ethylene does
not condense. Near the winter pole (80{\deg} N), some compounds (C
$_{4}$H $_{2}$, C $_{3}$H $_{4}$) exhibit an
(interior) minimum in the observed abundance vertical profiles, whereas
2D-CM profiles are well mixed all along the atmospheric column. This
minimum can be a diagnostic of the strength of the meridional
circulation, and of the spatial extension of the winter polar vortex
where strong descending motions are present. In the summer hemisphere,
observed stratospheric abundances are uniform in latitude, whereas the
model maintains a residual enrichment over the summer pole from the
spring cell due to a secondary meridional overturning between 1 and 50
mbar, at latitudes south of 40-50{\deg} S. The strength, as well as
spatial and temporal extensions of this structure are a difficulty, that
may be linked to possible misrepresentation of horizontally mixing
processes, due to the restricted 2-dimensional nature of the model. This
restriction should also be kept in mind as a possible source of other
  doi = {10.1016/j.icarus.2008.05.010},
  adsurl = {},
  localpdf = {REF/2008Icar..197..556C.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{De La Haye}, V. and {Waite}, J.~H. and {Cravens}, T.~E. and 
	{Robertson}, I.~P. and {Lebonnois}, S.},
  title = {{Coupled ion and neutral rotating model of Titan's upper atmosphere}},
  journal = {\icarus},
  year = 2008,
  volume = 197,
  pages = {110-136},
  abstract = {{A one-dimensional composition model of Titan's upper atmosphere is
constructed, coupling 36 neutral species and 47 ions. Energy inputs from
the Sun and from Saturn's magnetosphere and updated temperature and eddy
coefficient parameters are taken into account. A rotating technique at
constant latitude and varying local-time is proposed to account for the
diurnal variation of solar inputs. The contributions of
photodissocation, neutral chemistry, ion-neutral chemistry, and electron
recombination to neutral production are presented as a function of
altitude and local time. Local time-dependent mixing ratio and density
profiles are presented in the context of the T and T Cassini data and
are compared in detail to previous models. An independent and simplified
ion and neutral scheme (19-species) is also proposed for future
3D-purposes. The model results demonstrate that a complete understanding
of the chemistry of Titan's upper atmosphere requires an understanding
of the coupled ion and neutral chemistry. In particular, the ionospheric
chemistry makes significant contributions to production rates of several
important neutral species.
  doi = {10.1016/j.icarus.2008.03.022},
  adsurl = {},
  localpdf = {REF/2008Icar..197..110D.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lefèvre}, F. and {Bertaux}, J.-L. and {Clancy}, R.~T. and 
	{Encrenaz}, T. and {Fast}, K. and {Forget}, F. and {Lebonnois}, S. and 
	{Montmessin}, F. and {Perrier}, S.},
  title = {{Heterogeneous chemistry in the atmosphere of Mars}},
  journal = {\nat},
  year = 2008,
  volume = 454,
  pages = {971-975},
  abstract = {{Hydrogen radicals are produced in the martian atmosphere by the
photolysis of water vapour and subsequently initiate catalytic cycles
that recycle carbon dioxide from its photolysis product carbon monoxide.
These processes provide a qualitative explanation for the stability of
the atmosphere of Mars, which contains 95 per cent carbon dioxide.
Balancing carbon dioxide production and loss based on our current
understanding of the gas-phase chemistry in the martian atmosphere has,
however, proven to be difficult. Interactions between gaseous chemical
species and ice cloud particles have been shown to be key factors in the
loss of polar ozone observed in the Earth's stratosphere, and may
significantly perturb the chemistry of the Earth's upper troposphere.
Water-ice clouds are also commonly observed in the atmosphere of Mars
and it has been suggested previously that heterogeneous chemistry could
have an important impact on the composition of the martian atmosphere.
Here we use a state-of-the-art general circulation model together with
new observations of the martian ozone layer to show that model
simulations that include chemical reactions occurring on ice clouds lead
to much improved quantitative agreement with observed martian ozone
levels in comparison with model simulations based on gas-phase chemistry
alone. Ozone is readily destroyed by hydrogen radicals and is therefore
a sensitive tracer of the chemistry that regulates the atmosphere of
Mars. Our results suggest that heterogeneous chemistry on ice clouds
plays an important role in controlling the stability and composition of
the martian atmosphere.
  doi = {10.1038/nature07116},
  adsurl = {},
  localpdf = {REF/2008Natur.454..971L.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{S{\'a}nchez-Lavega}, A. and {Hueso}, R. and {Piccioni}, G. and 
	{Drossart}, P. and {Peralta}, J. and {Pérez-Hoyos}, S. and 
	{Wilson}, C.~F. and {Taylor}, F.~W. and {Baines}, K.~H. and 
	{Luz}, D. and {Erard}, S. and {Lebonnois}, S.},
  title = {{Variable winds on Venus mapped in three dimensions}},
  journal = {\grl},
  keywords = {Atmospheric Composition and Structure: Planetary atmospheres (5210, 5405, 5704), Planetary Sciences: Solar System Objects: Venus, Atmospheric Processes: General circulation (1223), Atmospheric Processes: Planetary meteorology (5445, 5739)},
  year = 2008,
  volume = 35,
  eid = {L13204},
  pages = {13204},
  abstract = {{We present zonal and meridional wind measurements at three altitude
levels within the cloud layers of Venus from cloud tracking using images
taken with the VIRTIS instrument on board Venus Express. At low
latitudes, zonal winds in the Southern hemisphere are nearly constant
with latitude with westward velocities of 105 ms$^{-1}$ at
cloud-tops (altitude \~{} 66 km) and 60-70 ms$^{-1}$ at the
cloud-base (altitude \~{} 47 km). At high latitudes, zonal wind speeds
decrease linearly with latitude with no detectable vertical wind shear
(values lower than 15 ms$^{-1}$), indicating the possibility of a
vertically coherent vortex structure. Meridional winds at the cloud-tops
are poleward with peak speed of 10 ms$^{-1}$ at 55{\deg} S but
below the cloud tops and averaged over the South hemisphere are found to
be smaller than 5 ms$^{-1}$. We also report the detection at
subpolar latitudes of wind variability due to the solar tide.
  doi = {10.1029/2008GL033817},
  adsurl = {},
  localpdf = {REF/2008GeoRL..3513204S.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Encrenaz}, T. and {Greathouse}, T.~K. and {Richter}, M.~J. and 
	{Bézard}, B. and {Fouchet}, T. and {Lefèvre}, F. and 
	{Montmessin}, F. and {Forget}, F. and {Lebonnois}, S. and {Atreya}, S.~K.
  title = {{Simultaneous mapping of H $_{2}$O and H $_{2}$O $_{2}$ on Mars from infrared high-resolution imaging spectroscopy}},
  journal = {\icarus},
  year = 2008,
  volume = 195,
  pages = {547-556},
  abstract = {{New maps of martian water vapor and hydrogen peroxide have been obtained
in November-December 2005, using the Texas Echelon Cross Echelle
Spectrograph (TEXES) at the NASA Infra Red Telescope facility (IRTF) at
Mauna Kea Observatory. The solar longitude L was 332{\deg} (end of
southern summer). Data have been obtained at 1235-1243 cm $^{-1}$,
with a spectral resolution of 0.016 cm $^{-1}$ ( R=8{\times}10).
The mean water vapor mixing ratio in the region [0{\deg}-55{\deg} S;
345{\deg}-45{\deg} W], at the evening limb, is 150{\plusmn}50 ppm
(corresponding to a column density of 8.3{\plusmn}2.8 pr-{$\mu$}m). The mean
water vapor abundance derived from our measurements is in global overall
agreement with the TES and Mars Express results, as well as the GCM
models, however its spatial distribution looks different from the GCM
predictions, with evidence for an enhancement at low latitudes toward
the evening side. The inferred mean H $_{2}$O $_{2}$
abundance is 15{\plusmn}10 ppb, which is significantly lower than the
June 2003 result [Encrenaz, T., Bézard, B., Greathouse, T.K.,
Richter, M.J., Lacy, J.H., Atreya, S.K., Wong, A.S., Lebonnois, S.,
Lefèvre, F., Forget, F., 2004. Icarus 170, 424-429] and lower
than expected from the photochemical models, taking in account the
change in season. Its spatial distribution shows some similarities with
the map predicted by the GCM but the discrepancy in the H $_{2}$O
$_{2}$ abundance remains to be understood and modeled.
  doi = {10.1016/j.icarus.2008.01.022},
  adsurl = {},
  localpdf = {REF/2008Icar..195..547E.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Sekine}, Y. and {Lebonnois}, S. and {Imanaka}, H. and {Matsui}, T. and 
	{Bakes}, E.~L.~O. and {McKay}, C.~P. and {Khare}, B.~N. and 
	{Sugita}, S.},
  title = {{The role of organic haze in Titan's atmospheric chemistry. II. Effect of heterogeneous reaction to the hydrogen budget and chemical composition of the atmosphere}},
  journal = {\icarus},
  year = 2008,
  volume = 194,
  pages = {201-211},
  abstract = {{One of the key components controlling the chemical composition and
climatology of Titan's atmosphere is the removal of reactive atomic
hydrogen from the atmosphere. A proposed process of the removal of
atomic hydrogen is the heterogeneous reaction with organic aerosol. In
this study, we investigate the effect of heterogeneous reactions in
Titan's atmospheric chemistry using new measurements of the
heterogeneous reaction rate [Sekine, Y., Imanaka, H., Matsui, T., Khare,
B.N., Bakes, E.L.O., McKay, C.P., Sugita, S., 2008. Icarus 194, 186-200]
in a one-dimensional photochemical model. Our results indicate that
60-75\% of the atomic hydrogen in the stratosphere and mesosphere are
consumed by the heterogeneous reactions. This result implies that the
heterogeneous reactions on the aerosol surface may predominantly remove
atomic hydrogen in Titan's stratosphere and mesosphere. The results of
our calculation also indicate that a low concentration of atomic
hydrogen enhances the concentrations of unsaturated complex organics,
such as C $_{4}$H $_{2}$ and phenyl radical, by more than
two orders in magnitude around 400 km in altitude. Such an increase in
unsaturated species may induce efficient haze production in Titan's
mesosphere and upper stratosphere. These results imply a positive
feedback mechanism in haze production in Titan's atmosphere. The
increase in haze production would affect the chemical composition of the
atmosphere, which might induce further haze production. Such a positive
feedback could tend to dampen the loss and supply cycles of CH
$_{4}$ due to an episodic CH $_{4}$ release into Titan's
  doi = {10.1016/j.icarus.2007.08.030},
  adsurl = {},
  localpdf = {REF/2008Icar..194..201S.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}