@comment{{This file has been generated by bib2bib 1.97}}
@comment{{Command line: bib2bib --quiet -c year=2018 -c $type="ARTICLE" -oc pub2018.txt -ob pub2018.bib}}
  author = {{Lebonnois}, S. and {Schubert}, G. and {Forget}, F. and {Spiga}, A.
  title = {{Planetary boundary layer and slope winds on Venus}},
  journal = {\icarus},
  keywords = {Venus, Atmosphere, Planetary boundary layer, Slope winds},
  year = 2018,
  volume = 314,
  pages = {149-158},
  abstract = {{Few constraints are available to characterize the deep atmosphere of
Venus, though this region is crucial to understand the interactions
between surface and atmosphere on Venus. Based on simulations performed
with the IPSL Venus Global Climate Model, the possible structure and
characteristics of Venus' planetary boundary layer (PBL) are
investigated. The vertical profile of the potential temperature in the
deepest 10 km above the surface and its diurnal variations are
controlled by radiative and dynamical processes. The model predicts a
diurnal cycle for the PBL activity, with a stable nocturnal PBL while
convective activity develops during daytime. The diurnal convective PBL
is strongly correlated with surface solar flux and is maximum around
noon and in low latitude regions. It typically reaches less than 2 km
above the surface, but its vertical extension is much higher over high
elevations, and more precisely over the western flanks of elevated
terrains. This correlation is explained by the impact of surface winds,
which undergo a diurnal cycle with downward katabatic winds at night and
upward anabatic winds during the day along the slopes of high-elevation
terrains. The convergence of these daytime anabatic winds induces upward
vertical winds, that are responsible for the correlation between height
of the convective boundary layer and topography.
  doi = {10.1016/j.icarus.2018.06.006},
  adsurl = {},
  localpdf = {REF/2018Icar..314..149L.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Garate-Lopez}, I. and {Lebonnois}, S.},
  title = {{Latitudinal variation of clouds' structure responsible for Venus' cold collar}},
  journal = {\icarus},
  keywords = {Venus atmosphere, Cold collar, Modelling},
  year = 2018,
  volume = 314,
  pages = {1-11},
  abstract = {{Global Climate Models (GCM) are very useful tools to study theoretically
the general dynamics and specific phenomena in planetary atmospheres. In
the case of Venus, several GCMs succeeded in reproducing the
atmosphere's superrotation and the global temperature field. However,
the highly variable polar temperature and the permanent cold collar
present at 60$^{o}$ -80$^{o}$ latitude have not been
reproduced satisfactorily yet.

Here we improve the radiative transfer scheme of the Institut Pierre
Simon Laplace Venus GCM in order to numerically simulate the polar
thermal features in Venus atmosphere. The main difference with the
previous model is that we now take into account the latitudinal
variation of the cloud structure. Both solar heating rates and infrared
cooling rates have been modified to consider the cloud top's altitude
decrease toward the poles and the variation in latitude of the different
particle modes' abundances.

A new structure that closely resembles the observed cold collar appears
in the average temperature field at 2 {\times}10$^{4}$ - 4
{\times}10$^{3}$  Pa ({\sim} 62 - 66  km) altitude range and
60$^{o}$ -90$^{o}$ latitude band. It is not isolated
from the pole as in the observation-based maps, but the obtained
temperature values (220 K) are in good agreement with observed values.
Temperature polar maps across this region show an inner warm region
where the polar vortex is observed, but the obtained 230 K average value
is colder than the observed mean value and the simulated horizontal
structure does not show the fine-scale features present within the

The comparison with a simulation that does not take into account the
latitudinal variation of the cloud structure in the infrared cooling
computation, shows that the cloud structure is essential in the cold
collar formation. Although our analysis focuses on the improvement of
the radiative forcing and the variations it causes in the thermal
structure, polar dynamics is definitely affected by this modified
environment and a noteworthy upwelling motion is found in the cold
collar area.
  doi = {10.1016/j.icarus.2018.05.011},
  adsurl = {},
  localpdf = {REF/2018Icar..314....1G.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Lef\`evre}, M. and {Lebonnois}, S. and {Spiga}, A.},
  title = {{Three-Dimensional Turbulence-Resolving Modeling of the Venusian Cloud Layer and Induced Gravity Waves: Inclusion of Complete Radiative Transfer and Wind Shear}},
  journal = {Journal of Geophysical Research (Planets)},
  keywords = {Venus, modeling, convection, gravity waves},
  year = 2018,
  volume = 123,
  pages = {2773-2789},
  abstract = {{Venus' convective cloud layers and associated gravity waves strongly
impact the local and global budget of heat, momentum, and chemical
species. Here we use for the first time three-dimensional
turbulence-resolving dynamical integrations of Venus' atmosphere from
the surface to 100-km altitude, coupled with fully interactive radiative
transfer computations. We show that this enables to correctly reproduce
the vertical position (46- to 55-km altitude) and thickness (9 km) of
the main convective cloud layer measured by Venus Express and Akatsuki
radio occultations, as well as the intensity of convective plumes (3
m/s) measured by VEGA balloons. Both the radiative forcing in the
visible and the large-scale dynamical impact play a role in the
variability of the cloud convective activity with local time and
latitude. Our model reproduces the diurnal cycle in cloud convection
observed by Akatsuki at the low latitudes and the lack thereof observed
by Venus Express at the equator. The observed enhancement of cloud
convection at high latitudes is simulated by our model, although
underestimated compared to observations. We show that the influence of
the vertical shear of horizontal superrotating winds must be accounted
for in our model to allow for gravity waves of the observed intensity
($\gt$1 K) and horizontal wavelength (up to 20 km) to be generated
through the obstacle effect mechanism. The vertical extent of our model
also allows us to predict for the first time a 7-km-thick convective
layer at the cloud top (70-km altitude) caused by the solar absorption
of the unknown ultraviolet absorber.
  doi = {10.1029/2018JE005679},
  adsurl = {},
  localpdf = {REF/2018JGRE..123.2773L.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Navarro}, T. and {Schubert}, G. and {Lebonnois}, S.},
  title = {{Atmospheric mountain wave generation on Venus and its influence on the solid planet's rotation rate}},
  journal = {Nature Geoscience},
  year = 2018,
  volume = 11,
  pages = {487-491},
  abstract = {{The Akatsuki spacecraft observed a 10,000-km-long meridional structure
at the top of the cloud deck of Venus that appeared stationary with
respect to the surface and was interpreted as a gravity wave.
Additionally, over four Venus solar days of observations, other such
waves were observed to appear in the afternoon over equatorial highland
regions. This indicates a direct influence of the solid planet on the
whole Venusian atmosphere despite dissimilar rotation rates of 243 and 4
days, respectively. How such gravity waves might be generated on Venus
is not understood. Here, we use general circulation model simulations of
the Venusian atmosphere to show that the observations are consistent
with stationary gravity waves over topographic highs{\mdash}or mountain
waves{\mdash}that are generated in the afternoon in equatorial regions by
the diurnal cycle of near-surface atmospheric stability. We find that
these mountain waves substantially contribute to the total atmospheric
torque that acts on the planet's surface. We estimate that mountain
waves, along with the thermal tide and baroclinic waves, can produce a
change in the rotation rate of the solid body of about 2 minutes per
solar day. This interplay between the solid planet and atmosphere may
explain some of the difference in rotation rates (equivalent to a change
in the length of day of about 7 minutes) measured by spacecraft over the
past 40 years.
  doi = {10.1038/s41561-018-0157-x},
  adsurl = {},
  localpdf = {REF/2018NatGe..11..487N.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Read}, P.~L. and {Lebonnois}, S.},
  title = {{Superrotation on Venus, on Titan, and Elsewhere}},
  journal = {Annual Review of Earth and Planetary Sciences},
  year = 2018,
  volume = 46,
  pages = {175-202},
  abstract = {{The superrotation of the atmospheres of Venus and Titan has puzzled
dynamicists for many years and seems to put these planets in a very
different dynamical regime from most other planets. In this review, we
consider how to define superrotation objectively and explore the
constraints that determine its occurrence. Atmospheric superrotation
also occurs elsewhere in the Solar System and beyond, and we compare
Venus and Titan with Earth and other planets for which wind estimates
are available. The extreme superrotation on Venus and Titan poses some
difficult challenges for numerical models of atmospheric circulation,
much more difficult than for more rapidly rotating planets such as Earth
or Mars. We consider mechanisms for generating and maintaining a
superrotating state, all of which involve a global meridional
overturning circulation. The role of nonaxisymmetric eddies is crucial,
however, but the detailed mechanisms may differ between Venus, Titan,
and other planets.
  doi = {10.1146/annurev-earth-082517-010137},
  adsurl = {},
  localpdf = {REF/2018AREPS..46..175R.pdf},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System}
  author = {{Sylvestre}, M. and {Teanby}, N.~A. and {Vinatier}, S. and {Lebonnois}, S. and 
	{Irwin}, P.~G.~J.},
  title = {{Seasonal evolution of C$_{2}$N$_{2}$, C$_{3}$H$_{4}$, and C$_{4}$H$_{2}$ abundances in Titan's lower stratosphere}},
  journal = {\aap},
  archiveprefix = {arXiv},
  eprint = {1709.09979},
  primaryclass = {astro-ph.EP},
  keywords = {planets and satellites: atmospheres, methods: data analysis},
  year = 2018,
  volume = 609,
  eid = {A64},
  pages = {A64},
  abstract = {{
Aims: We study the seasonal evolution of Titan's lower stratosphere (around 15 mbar) in order to better understand the atmospheric dynamics and chemistry in this part of the atmosphere.
Methods: We analysed Cassini/CIRS far-IR observations from 2006 to 2016 in order to measure the seasonal variations of three photochemical by-products: C$_{4}$H$_{2}$, C$_{3}$H$_{4}$, and C$_{2}$N$_{2}$.
Results: We show that the abundances of these three gases have evolved significantly at northern and southern high latitudes since 2006. We measure a sudden and steep increase of the volume mixing ratios of C$_{4}$H$_{2}$, C$_{3}$H$_{4}$, and C$_{2}$N$_{2}$ at the south pole from 2012 to 2013, whereas the abundances of these gases remained approximately constant at the north pole over the same period. At northern mid-latitudes, C$_{2}$N$_{2}$ and C$_{4}$H$_{2}$ abundances decrease after 2012 while C$_{3}$H$_{4}$ abundances stay constant. The comparison of these volume mixing ratio variations with the predictions of photochemical and dynamical models provides constraints on the seasonal evolution of atmospheric circulation and chemical processes at play. }}, doi = {10.1051/0004-6361/201630255}, adsurl = {}, localpdf = {REF/2018A_26A...609A..64S.pdf}, adsnote = {Provided by the SAO/NASA Astrophysics Data System} }