The Experts below are selected from a list of 8295 Experts worldwide ranked by ideXlab platform
Ann Carine Vandaele - One of the best experts on this subject based on the ideXlab platform.
-
preparing envision so2 measurements below and above Venus clouds
EPSC-DPS Joint Meeting 2019 15-20 September 2019 Geneva Switzerland, 2020Co-Authors: Emmanuel Marcq, Lucio Baggio, Kandis Lea Jessup, I Amine, M Duquesnoy, Thérèse Encrenaz, Franck Lefevre, Franck Montmessin, Jean-loup Bertaux, Ann Carine VandaeleAbstract:One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenic species in Venus’ Atmosphere, one of the most prominent being sulphur dioxide (SO2). Monitoring SO2 below the clouds can be performed on the nightside near 2.4 μm, and is one science objective of the VenSpec-H channel (P.I.: A. C. Vandaele, BIRA) onboard EnVision. Monitoring SO2 above the clouds can be performed on the dayside in the 200-300nm range, and is the main science objective of the VenSpec-U channel (P.I.: E. Marcq, LATMOS). Here we present the analysis of two analogous datasets, namely IRTF/iSHELL ground based observations on the nightside of Venus, and the most recent reanalaysis of the Venus Express/SPICAV-UV dataset on the dayside of Venus.
-
preparing envision so 2 measurements below and above Venus clouds
EPSC-DPS Joint Meeting 2019, 2019Co-Authors: Emmanuel Marcq, Lucio Baggio, Kandis Lea Jessup, I Amine, M Duquesnoy, E T Encrenaz, Franck Lefevre, Franck Montmessin, Jean-loup Bertaux, Ann Carine VandaeleAbstract:One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenicspecies in Venus’ Atmosphere, one of the most promi-nent being sulphur dioxide (SO2). Monitoring SO2below the clouds can be performed on the night-side near2.4μm, and is one science objective of theVenSpec-H channel (P.I.: A. C. Vandaele, BIRA) on-board EnVision. Monitoring SO2above the cloudscan be performed on the dayside in the200-300 nmrange, and is the main science objective of theVenSpec-U channel (P.I.: E. Marcq, LATMOS). Herewe present the analysis of two analogous datasets,namely IRTF/iSHELL ground based observations onthe nightside of Venus, and the most recent reanalay-sis of the Venus Express/SPICAV-UV dataset on thedayside of Venus
-
sulfur dioxide in the Venus Atmosphere ii spatial and temporal variability
Icarus, 2017Co-Authors: Ann Carine Vandaele, Kandis Lea Jessup, Thérèse Encrenaz, Denis Belyaev, Oleg Korablev, S. Chamberlain, Daria Evdokimova, L W Esposito, Franck LefevreAbstract:The vertical distribution of sulfur species in the Venus Atmosphere has been investigated and discussed in Part I of this series of papers dealing with the variability of SO2 on Venus. In this second part, we focus our attention on the spatial (horizontal) and temporal variability exhibited by SO2. Appropriate data sets – SPICAV/UV nadir observations from Venus Express, ground-based ALMA and TEXES, as well as UV observation on the Hubble Space Telescope – have been considered for this analysis. High variability both on short-term and short-scale are observed. The long-term trend observed by these instruments shows a succession of rapid increases followed by slow decreases in the SO2 abundance at the cloud top level, implying that the transport of air from lower altitudes plays an important role. The origins of the larger amplitude short-scale, short-term variability observed at the cloud tops are not yet known but are likely also connected to variations in vertical transport of SO2 and possibly to variations in the abundance and production and loss of H2O, H2SO4, and Sx.
-
Sulfur dioxide in the Venus Atmosphere: I. Vertical distribution and variability
Icarus, 2017Co-Authors: Ann Carine Vandaele, Kandis Lea Jessup, Thérèse Encrenaz, Franck Lefevre, Denis Belyaev, Oleg Korablev, Sarah Chamberlain, Daria Evdokimova, Larry Esposito, Sanjay LimayeAbstract:Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is closely linked to the global-scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Sulfur oxide observations provide therefore important insight into the on-going chemical evolution of Venus’ Atmosphere, atmospheric dynamics, and possible volcanism. This paper is the first of a series of two investigating the SO2 and SO variability in the Venus Atmosphere. This first part of the study will focus on the vertical distribution of SO2, considering mostly observations performed by instruments and techniques providing accurate vertical information. This comprises instruments in space (SPICAV/SOIR suite on board Venus Express) and Earth-based instruments (JCMT). The most noticeable feature of the vertical profile of the SO2 abundance in the Venus Atmosphere is the presence of an inversion layer located at about 70–75 km, with VMRs increasing above. The observations presented in this compilation indicate that at least one other significant sulfur reservoir (in addition to SO2 and SO) must be present throughout the 70–100 km altitude region to explain the inversion in the SO2 vertical profile. No photochemical model has an explanation for this behaviour. GCM modelling indicates that dynamics may play an important role in generating an inflection point at 75 km altitude but does not provide a definitive explanation of the source of the inflection at all local times or latitudes The current study has been carried out within the frame of the International Space Science Institute (ISSI) International Team entitled ‘SO2 variability in the Venus Atmosphere’.
-
contribution from soir vex to the updated Venus international reference Atmosphere vira
Advances in Space Research, 2016Co-Authors: Ann Carine Vandaele, A. Mahieux, Denis Belyaev, V. Wilquet, S. Chamberlain, Bojan Ristic, Severine Robert, I R Thomas, Loic Trompet, Anna FedorovaAbstract:The SOIR instrument on-board Venus Express is an infrared spectrometer covering the 2.2 - 4.3 μm spectral region. This instrument allows the detection of several key species of the Venus Atmosphere, including CO2, CO, H2O/HDO, HCl, HF and SO2. From the CO2 density measurements, temperature is inferred giving information on the thermal structure of the Atmosphere. Here we described the kind of data (profiles, latitudinal average, etc.) that will be provided to the updated VIRA compilation.
A. Mahieux - One of the best experts on this subject based on the ideXlab platform.
-
The thermal structure of the Venus Atmosphere: Intercomparison of Venus Express and ground based observations of vertical temperature and density profiles
Icarus, 2017Co-Authors: Sanjay S. Limaye, A. Mahieux, S.w. Bougher, Sébastien Lebonnois, Martin Pätzold, Sean Bruinsma, Sarah Chamberlain, R. Todd Clancy, Jean-claude Gérard, Gabriella GilliAbstract:The Venus International Reference Atmosphere (VIRA) model contains tabulated values of temperature and number densities obtained by the experiments on the Venera entry probes, Pioneer Venus Orbiter and multi-probe missions in the 1980s. The instruments on the recent Venus Express orbiter mission generated a significant amount of new observational data on the vertical and horizontal structure of the Venus Atmosphere from 40 km to about 180 km altitude from April 2006 to November 2014. Many ground based experiments have provided data on the upper Atmosphere (90-130 km) temperature structure since the publication of VIRA in 1985. The "Thermal Structure of the Venus Atmosphere" Team was supported by the International Space Studies Institute (ISSI), Bern, Switzerland, from 2013 to 2015 in order to combine and compare the ground-based observations and the VEx observations of the thermal structure as a first step towards generating an updated VIRA model. Results of this comparison are presented in five latitude bins and three local time bins by assuming hemispheric symmetry. The intercomparison of the ground-based and VEx results provides for the first time a consistent picture of the temperature and density structure in the 40 km–180 km altitude range. The Venus Express observations have considerably increased our knowledge of the Venus atmospheric thermal structure above ∼40 km and provided new information above 100 km. There are, however, still observational gaps in latitude and local time above certain regions. Considerable variability in the temperatures and densities is seen above 100 km but certain features appear to be systematically present, such as a succession of warm and cool layers. Preliminary modeling studies support the existence of such layers in agreement with a global scale circulation. The intercomparison focuses on average profiles but some VEx experiments provide sufficient global coverage to identify solar thermal tidal components. The differences between the VEx temperature profiles and the VIRA below 0.1 mbar/95 km are small. There is, however, a clear discrepancy at high latitudes in the 10-30 mbar (70-80 km) range. The VEx observations will also allow the improvement of the empirical models (VTS3 by Hedin et al., 1983 and VIRA by Keating et al., 1985) above 0.03 mbar/100 km, in particular the 100-150 km region where a sufficient observational coverage was previously missing. The next steps in order to define the updated VIRA temperature structure up to 150 km altitude are (1) define the grid on which this database may be provided, (2) fill what is possible with the results of the data intercomparison, and (3) fill the observational gaps. An interpolation between the datasets may be performed by using available General Circulation Models as guidelines. An improved spatial coverage of observations is still necessary at all altitudes, in latitude-longitude and at all local solar times for a complete description of the atmospheric thermal structure, in particular on the dayside above 100 km. New in-situ observations in the Atmosphere below 40 km are missing, an altitude region that cannot be accessed by occultation experiments. All these questions need to be addressed by future missions.
-
contribution from soir vex to the updated Venus international reference Atmosphere vira
Advances in Space Research, 2016Co-Authors: Ann Carine Vandaele, A. Mahieux, Denis Belyaev, V. Wilquet, S. Chamberlain, Bojan Ristic, Severine Robert, I R Thomas, Loic Trompet, Anna FedorovaAbstract:The SOIR instrument on-board Venus Express is an infrared spectrometer covering the 2.2 - 4.3 μm spectral region. This instrument allows the detection of several key species of the Venus Atmosphere, including CO2, CO, H2O/HDO, HCl, HF and SO2. From the CO2 density measurements, temperature is inferred giving information on the thermal structure of the Atmosphere. Here we described the kind of data (profiles, latitudinal average, etc.) that will be provided to the updated VIRA compilation.
-
Sulfur Dioxide variability in the Venus Atmosphere
2015Co-Authors: A.c. Vandaele, A. Mahieux, Thérèse Encrenaz, V. Wilquet, S. Chamberlain, Larry Esposito, O. Korablev, D. Belayev, K.l. Jessup, Franck LefevreAbstract:Recent observations of sulfur oxides (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Particularly intriguing are the layer of enhanced gas- phase SO2 and SO in the upper mesosphere, and variability in the maximum observed SO2 abundance and the equator-to-pole SO2 abundance gradient, seemingly on multi-year cycles, that is not uniquely linked to local time variations. Sulfur oxide chemistry on Venus is closely linked to the global- scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Consequently, sulfur oxide observations provide important insight into the ongoing chemical evolution of Venus’ Atmosphere, atmospheric dynamics, and possible volcanism. Existing observations have been obtained using multiple platforms, observing techniques, and wavelengths. Each has its own unique strengths and limitations. Although there is strong agreement on some features, there are significant unresolved apparent disagreements among current observations and between observations and models. These apparent disagreements need to be analyzed and assessed carefully to synthesize a clear understanding of sulfur oxide chemistry on Venus. These investigations have been performed via 1) the comparison and validation of observations, from past missions, Venus Express, Earth-based telescopes, and the Earth-orbiting Hubble Space Telescope; and 2) modelling of the SO2 and sulfur-oxide family photochemistry. The current study has been carried out within the frame of the ISSI International Team entitled ‘SO2 variability in the Venus Atmosphere’.
-
thermal structure of Venus nightside upper Atmosphere measured by stellar occultations with spicav Venus express
Planetary and Space Science, 2015Co-Authors: A. Mahieux, Franck Montmessin, Denis Belyaev, Anna Fedorova, Emmanuel Marcq, Jean-loup Bertaux, Arianna Piccialli, Silvia TellmannAbstract:The thermal structure of Venus upper Atmosphere (90–140 km) was investigated using stellar occultation measurements acquired by the SPICAV experiment on board Venus Express. The SPICAV ultraviolet channel provides CO2 local density and temperature vertical profiles with a vertical resolution of View the MathML source of both the southern and the northern hemispheres on the nightside (18:00-06:00 hr local time). A permanent layer of warm air is observed at the mesopause in the altitude range 90–100 km. Temperature then decreases with increasing altitude reaching a minimum value around 125 km. Spatial and temporal changes in the thermal structure have been analyzed. Local time variations dominate the structure of Venus Atmosphere at these altitudes: temperatures show an increase of View the MathML source on the morning side compared to the evening side. The homopause altitude was also determined; it varies between 119 and 138 km of altitude, increasing from the evening side to the morning side. SPICAV temperature profiles were compared to several literature results from ground-based observations, previous spacecraft missions and the Venus Express mission.
-
Update of the Venus density and temperature profiles at high altitude measured by SOIR on board Venus Express
Planetary and Space Science, 2015Co-Authors: A. Mahieux, Franck Montmessin, A.c. Vandaele, S.w. Bougher, R. Drummond, S. Robert, V. Wilquet, S. Chamberlain, Arianna Piccialli, S. TellmannAbstract:The SOIR instrument on board Venus Express regularly sounds the Venus Atmosphere using the solar occultation technique. The density and temperature profiles are inferred from SOIR spectra recorded in the infrared. The method has been described in a previous publication (Mahieux et al., 2012. J. Geophys. Res. 117. doi:10.1029/2012JE004058.). This paper is devoted to the update of the VAST (Venus Atmosphere from SOIR measurements at the Terminator) compilation that was initiated in the above cited work, which gives the mean CO2 number density and temperature profiles for different latitude bins. The method has been improved and has been applied to more data. The new compilation which is given on the same latitudinal grid now distinguishes between the two sides of the terminator. The compilation also confirms the main thermal layering characteristics that were identified in the earlier version: the succession of a warm layer (230±30 K, 1−σ standard deviation) at a pressure level of 3.2×10−7 mbar (~140 km), a very cold layer (125±32 K) at 2.5×10−5 mbar (~123 km), a warm layer (204±17 K) at 0.01 mbar (~102 km) and finally a colder layer at 0.4 mbar (171±34 K, ~87 km). The layering of all the temperature profiles is explained by radiative rather than dynamical processes. The temporal temperature variation is larger than the mean latitudinal temperature variation. VAST is compared with temperature profiles obtained from other Venus Express instruments, VeRa and SPICAV–UV, and ground based measurements.
Oleg Korablev - One of the best experts on this subject based on the ideXlab platform.
-
sulfur dioxide in the Venus Atmosphere ii spatial and temporal variability
Icarus, 2017Co-Authors: Ann Carine Vandaele, Kandis Lea Jessup, Thérèse Encrenaz, Denis Belyaev, Oleg Korablev, S. Chamberlain, Daria Evdokimova, L W Esposito, Franck LefevreAbstract:The vertical distribution of sulfur species in the Venus Atmosphere has been investigated and discussed in Part I of this series of papers dealing with the variability of SO2 on Venus. In this second part, we focus our attention on the spatial (horizontal) and temporal variability exhibited by SO2. Appropriate data sets – SPICAV/UV nadir observations from Venus Express, ground-based ALMA and TEXES, as well as UV observation on the Hubble Space Telescope – have been considered for this analysis. High variability both on short-term and short-scale are observed. The long-term trend observed by these instruments shows a succession of rapid increases followed by slow decreases in the SO2 abundance at the cloud top level, implying that the transport of air from lower altitudes plays an important role. The origins of the larger amplitude short-scale, short-term variability observed at the cloud tops are not yet known but are likely also connected to variations in vertical transport of SO2 and possibly to variations in the abundance and production and loss of H2O, H2SO4, and Sx.
-
Sulfur dioxide in the Venus Atmosphere: I. Vertical distribution and variability
Icarus, 2017Co-Authors: Ann Carine Vandaele, Kandis Lea Jessup, Thérèse Encrenaz, Franck Lefevre, Denis Belyaev, Oleg Korablev, Sarah Chamberlain, Daria Evdokimova, Larry Esposito, Sanjay LimayeAbstract:Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is closely linked to the global-scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Sulfur oxide observations provide therefore important insight into the on-going chemical evolution of Venus’ Atmosphere, atmospheric dynamics, and possible volcanism. This paper is the first of a series of two investigating the SO2 and SO variability in the Venus Atmosphere. This first part of the study will focus on the vertical distribution of SO2, considering mostly observations performed by instruments and techniques providing accurate vertical information. This comprises instruments in space (SPICAV/SOIR suite on board Venus Express) and Earth-based instruments (JCMT). The most noticeable feature of the vertical profile of the SO2 abundance in the Venus Atmosphere is the presence of an inversion layer located at about 70–75 km, with VMRs increasing above. The observations presented in this compilation indicate that at least one other significant sulfur reservoir (in addition to SO2 and SO) must be present throughout the 70–100 km altitude region to explain the inversion in the SO2 vertical profile. No photochemical model has an explanation for this behaviour. GCM modelling indicates that dynamics may play an important role in generating an inflection point at 75 km altitude but does not provide a definitive explanation of the source of the inflection at all local times or latitudes The current study has been carried out within the frame of the International Space Science Institute (ISSI) International Team entitled ‘SO2 variability in the Venus Atmosphere’.
-
sulfur dioxide above Venus clouds sounding by orbital solar occultations in uv and ir ranges
EGUGA, 2010Co-Authors: Denis Belyaev, A. Mahieux, Ann Carine Vandaele, Franck Montmessin, Anna Fedorova, Oleg Korablev, Jean-loup Bertaux, Emmanuel MarcqAbstract:Sulfur dioxide (SO2) is one of key components in Venus' Atmosphere. This gas participates in active photochemical life around Venus' clouds that consist of H2SO4 droplets and completely enshroud the planet. Behavior of SO2 within and above the clouds may be significant indicator of their dynamics and possible geological activity on the planet's surface. SO2 on Venus has been being explored for 40 years with mainly nadir observations. Nowadays the SPICAV/SOIR instrument onboard Venus Express orbiter is measuring content of sulfur dioxide either by nadir or by occultation soundings that provides a global SO2 monitoring above Venus' clouds. Here we present results from joint solar occultation experiment by SPICAV spectrometer in UV and SOIR spectrometer in IR. The first one gives vertical distribution of sulfur dioxide in absorption band 215 nm at altitudes 85-110 km, the second one sounds SO2 in a band around 4 μm at altitudes 65-75 km. Our equipment is not sensitive to the gas detection in-between 75-85 km because of its photochemical and absorption features in UV and IR. At Venus' clouds top (65-75 km) SO2 mixing ratio varies from 0.05 to 1 ppm depending on latitude and local time (morning or evening). Such variability is confirmed by nadir observations performed by the SPICAV in UV range [Marcq et al., 2010]. From UV occultation data the mixing ratio is also unstable: from 0.1 to 1 ppm at 85-110 km.
-
composition of the Venus mesosphere measured by solar occultation at infrared on board Venus express
Journal of Geophysical Research, 2008Co-Authors: Ann Carine Vandaele, A. Mahieux, Denis Belyaev, Anna Fedorova, Oleg Korablev, V. Wilquet, M De Maziere, Rachel Drummond, E Neefs, Franck MontmessinAbstract:Solar Occultation at Infrared (SOIR), which is a part of the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument on board Venus Express, combines an echelle-grating spectrometer with an acoustooptical tunable filter. It performs solar occultation measurements in the IR region at a high spectral resolution better than all previously flown planetary spectrometers. The wavelength range probed allows for a detailed chemical inventory of the Venus Atmosphere above the cloud layer, with an emphasis on the vertical distribution of the gases. A general description of the retrieval technique is given and is illustrated by some results obtained for CO2 and for a series of minor constituents, such as H2O, HDO, CO, HCl, and HF. Detection limits for previously undetected species will also be discussed.
-
line parameters for the 01111 00001 band of 12c16o18o from soir measurements of the Venus Atmosphere
Journal of Quantitative Spectroscopy & Radiative Transfer, 2008Co-Authors: V. Wilquet, A. Mahieux, Ann Carine Vandaele, Franck Montmessin, Anna Fedorova, Oleg Korablev, Valery I Perevalov, Sergei A Tashkun, R DahooAbstract:Abstract CO2 is the major constituent of the Atmosphere of Venus. Absorption lines due to its 12C16O18O isotopologue have been observed for the first time in Venus spectra in the 2930–3015 cm−1 spectral region, where the HITRAN database does not contain any line from this isotopologue. The measurements were performed by the SOIR instrument, which is part of the SPICAV/SOIR instrument on board the Venus Express mission of ESA. SOIR measured the atmospheric transmission of the upper Atmosphere of Venus (z>70 km) by performing a solar occultation experiment using the Atmosphere as a gigantic absorption cell. The identification of this newly observed band was first made recently from Mars Atmosphere observations by US colleagues. We have made independent theoretical calculations of the positions of the lines of this new 01111–00001 absorption band, which coincide perfectly with the positions of the observed lines. Assuming an oxygen isotopic ratio similar to the one measured previously in the lower Atmosphere of Venus, the line strengths of each observed line are deduced and listed.
Franck Montmessin - One of the best experts on this subject based on the ideXlab platform.
-
preparing envision so2 measurements below and above Venus clouds
EPSC-DPS Joint Meeting 2019 15-20 September 2019 Geneva Switzerland, 2020Co-Authors: Emmanuel Marcq, Lucio Baggio, Kandis Lea Jessup, I Amine, M Duquesnoy, Thérèse Encrenaz, Franck Lefevre, Franck Montmessin, Jean-loup Bertaux, Ann Carine VandaeleAbstract:One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenic species in Venus’ Atmosphere, one of the most prominent being sulphur dioxide (SO2). Monitoring SO2 below the clouds can be performed on the nightside near 2.4 μm, and is one science objective of the VenSpec-H channel (P.I.: A. C. Vandaele, BIRA) onboard EnVision. Monitoring SO2 above the clouds can be performed on the dayside in the 200-300nm range, and is the main science objective of the VenSpec-U channel (P.I.: E. Marcq, LATMOS). Here we present the analysis of two analogous datasets, namely IRTF/iSHELL ground based observations on the nightside of Venus, and the most recent reanalaysis of the Venus Express/SPICAV-UV dataset on the dayside of Venus.
-
preparing envision so 2 measurements below and above Venus clouds
EPSC-DPS Joint Meeting 2019, 2019Co-Authors: Emmanuel Marcq, Lucio Baggio, Kandis Lea Jessup, I Amine, M Duquesnoy, E T Encrenaz, Franck Lefevre, Franck Montmessin, Jean-loup Bertaux, Ann Carine VandaeleAbstract:One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenicspecies in Venus’ Atmosphere, one of the most promi-nent being sulphur dioxide (SO2). Monitoring SO2below the clouds can be performed on the night-side near2.4μm, and is one science objective of theVenSpec-H channel (P.I.: A. C. Vandaele, BIRA) on-board EnVision. Monitoring SO2above the cloudscan be performed on the dayside in the200-300 nmrange, and is the main science objective of theVenSpec-U channel (P.I.: E. Marcq, LATMOS). Herewe present the analysis of two analogous datasets,namely IRTF/iSHELL ground based observations onthe nightside of Venus, and the most recent reanalay-sis of the Venus Express/SPICAV-UV dataset on thedayside of Venus
-
microphysical modeling of the Venusian clouds with the ipsl Venus gcm
European Planetary Science Congress 2017, 2017Co-Authors: Sabrina Guilbon, Franck Montmessin, Sébastien Lebonnois, Anni Maattanen, Jeremie Burgalat, Kevin Mcgouldrick, Aurelien Stolzenbach, Franck LefevreAbstract:To understand the Venus Atmosphere, LMD and LATMOS laboratories have developed a 3D IPSL Venus Global Climate Model (Lebonnois et al. 2010). In this GCM, the cloud description is simplified. As clouds play a crucial role in radiative transfer, dynamics and generally the climate of Venus, it is necessary to improve the VGCM with a microphysical representation.
-
thermal structure of Venus nightside upper Atmosphere measured by stellar occultations with spicav Venus express
Planetary and Space Science, 2015Co-Authors: A. Mahieux, Franck Montmessin, Denis Belyaev, Anna Fedorova, Emmanuel Marcq, Jean-loup Bertaux, Arianna Piccialli, Silvia TellmannAbstract:The thermal structure of Venus upper Atmosphere (90–140 km) was investigated using stellar occultation measurements acquired by the SPICAV experiment on board Venus Express. The SPICAV ultraviolet channel provides CO2 local density and temperature vertical profiles with a vertical resolution of View the MathML source of both the southern and the northern hemispheres on the nightside (18:00-06:00 hr local time). A permanent layer of warm air is observed at the mesopause in the altitude range 90–100 km. Temperature then decreases with increasing altitude reaching a minimum value around 125 km. Spatial and temporal changes in the thermal structure have been analyzed. Local time variations dominate the structure of Venus Atmosphere at these altitudes: temperatures show an increase of View the MathML source on the morning side compared to the evening side. The homopause altitude was also determined; it varies between 119 and 138 km of altitude, increasing from the evening side to the morning side. SPICAV temperature profiles were compared to several literature results from ground-based observations, previous spacecraft missions and the Venus Express mission.
-
Update of the Venus density and temperature profiles at high altitude measured by SOIR on board Venus Express
Planetary and Space Science, 2015Co-Authors: A. Mahieux, Franck Montmessin, A.c. Vandaele, S.w. Bougher, R. Drummond, S. Robert, V. Wilquet, S. Chamberlain, Arianna Piccialli, S. TellmannAbstract:The SOIR instrument on board Venus Express regularly sounds the Venus Atmosphere using the solar occultation technique. The density and temperature profiles are inferred from SOIR spectra recorded in the infrared. The method has been described in a previous publication (Mahieux et al., 2012. J. Geophys. Res. 117. doi:10.1029/2012JE004058.). This paper is devoted to the update of the VAST (Venus Atmosphere from SOIR measurements at the Terminator) compilation that was initiated in the above cited work, which gives the mean CO2 number density and temperature profiles for different latitude bins. The method has been improved and has been applied to more data. The new compilation which is given on the same latitudinal grid now distinguishes between the two sides of the terminator. The compilation also confirms the main thermal layering characteristics that were identified in the earlier version: the succession of a warm layer (230±30 K, 1−σ standard deviation) at a pressure level of 3.2×10−7 mbar (~140 km), a very cold layer (125±32 K) at 2.5×10−5 mbar (~123 km), a warm layer (204±17 K) at 0.01 mbar (~102 km) and finally a colder layer at 0.4 mbar (171±34 K, ~87 km). The layering of all the temperature profiles is explained by radiative rather than dynamical processes. The temporal temperature variation is larger than the mean latitudinal temperature variation. VAST is compared with temperature profiles obtained from other Venus Express instruments, VeRa and SPICAV–UV, and ground based measurements.
Franck Lefevre - One of the best experts on this subject based on the ideXlab platform.
-
preparing envision so2 measurements below and above Venus clouds
EPSC-DPS Joint Meeting 2019 15-20 September 2019 Geneva Switzerland, 2020Co-Authors: Emmanuel Marcq, Lucio Baggio, Kandis Lea Jessup, I Amine, M Duquesnoy, Thérèse Encrenaz, Franck Lefevre, Franck Montmessin, Jean-loup Bertaux, Ann Carine VandaeleAbstract:One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenic species in Venus’ Atmosphere, one of the most prominent being sulphur dioxide (SO2). Monitoring SO2 below the clouds can be performed on the nightside near 2.4 μm, and is one science objective of the VenSpec-H channel (P.I.: A. C. Vandaele, BIRA) onboard EnVision. Monitoring SO2 above the clouds can be performed on the dayside in the 200-300nm range, and is the main science objective of the VenSpec-U channel (P.I.: E. Marcq, LATMOS). Here we present the analysis of two analogous datasets, namely IRTF/iSHELL ground based observations on the nightside of Venus, and the most recent reanalaysis of the Venus Express/SPICAV-UV dataset on the dayside of Venus.
-
preparing envision so 2 measurements below and above Venus clouds
EPSC-DPS Joint Meeting 2019, 2019Co-Authors: Emmanuel Marcq, Lucio Baggio, Kandis Lea Jessup, I Amine, M Duquesnoy, E T Encrenaz, Franck Lefevre, Franck Montmessin, Jean-loup Bertaux, Ann Carine VandaeleAbstract:One of the primary objectives of the preselected En-Vision M5 proposal is the monitoring of volcanogenicspecies in Venus’ Atmosphere, one of the most promi-nent being sulphur dioxide (SO2). Monitoring SO2below the clouds can be performed on the night-side near2.4μm, and is one science objective of theVenSpec-H channel (P.I.: A. C. Vandaele, BIRA) on-board EnVision. Monitoring SO2above the cloudscan be performed on the dayside in the200-300 nmrange, and is the main science objective of theVenSpec-U channel (P.I.: E. Marcq, LATMOS). Herewe present the analysis of two analogous datasets,namely IRTF/iSHELL ground based observations onthe nightside of Venus, and the most recent reanalay-sis of the Venus Express/SPICAV-UV dataset on thedayside of Venus
-
sulfur dioxide in the Venus Atmosphere ii spatial and temporal variability
Icarus, 2017Co-Authors: Ann Carine Vandaele, Kandis Lea Jessup, Thérèse Encrenaz, Denis Belyaev, Oleg Korablev, S. Chamberlain, Daria Evdokimova, L W Esposito, Franck LefevreAbstract:The vertical distribution of sulfur species in the Venus Atmosphere has been investigated and discussed in Part I of this series of papers dealing with the variability of SO2 on Venus. In this second part, we focus our attention on the spatial (horizontal) and temporal variability exhibited by SO2. Appropriate data sets – SPICAV/UV nadir observations from Venus Express, ground-based ALMA and TEXES, as well as UV observation on the Hubble Space Telescope – have been considered for this analysis. High variability both on short-term and short-scale are observed. The long-term trend observed by these instruments shows a succession of rapid increases followed by slow decreases in the SO2 abundance at the cloud top level, implying that the transport of air from lower altitudes plays an important role. The origins of the larger amplitude short-scale, short-term variability observed at the cloud tops are not yet known but are likely also connected to variations in vertical transport of SO2 and possibly to variations in the abundance and production and loss of H2O, H2SO4, and Sx.
-
microphysical modeling of the Venusian clouds with the ipsl Venus gcm
European Planetary Science Congress 2017, 2017Co-Authors: Sabrina Guilbon, Franck Montmessin, Sébastien Lebonnois, Anni Maattanen, Jeremie Burgalat, Kevin Mcgouldrick, Aurelien Stolzenbach, Franck LefevreAbstract:To understand the Venus Atmosphere, LMD and LATMOS laboratories have developed a 3D IPSL Venus Global Climate Model (Lebonnois et al. 2010). In this GCM, the cloud description is simplified. As clouds play a crucial role in radiative transfer, dynamics and generally the climate of Venus, it is necessary to improve the VGCM with a microphysical representation.
-
Sulfur dioxide in the Venus Atmosphere: I. Vertical distribution and variability
Icarus, 2017Co-Authors: Ann Carine Vandaele, Kandis Lea Jessup, Thérèse Encrenaz, Franck Lefevre, Denis Belyaev, Oleg Korablev, Sarah Chamberlain, Daria Evdokimova, Larry Esposito, Sanjay LimayeAbstract:Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is closely linked to the global-scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Sulfur oxide observations provide therefore important insight into the on-going chemical evolution of Venus’ Atmosphere, atmospheric dynamics, and possible volcanism. This paper is the first of a series of two investigating the SO2 and SO variability in the Venus Atmosphere. This first part of the study will focus on the vertical distribution of SO2, considering mostly observations performed by instruments and techniques providing accurate vertical information. This comprises instruments in space (SPICAV/SOIR suite on board Venus Express) and Earth-based instruments (JCMT). The most noticeable feature of the vertical profile of the SO2 abundance in the Venus Atmosphere is the presence of an inversion layer located at about 70–75 km, with VMRs increasing above. The observations presented in this compilation indicate that at least one other significant sulfur reservoir (in addition to SO2 and SO) must be present throughout the 70–100 km altitude region to explain the inversion in the SO2 vertical profile. No photochemical model has an explanation for this behaviour. GCM modelling indicates that dynamics may play an important role in generating an inflection point at 75 km altitude but does not provide a definitive explanation of the source of the inflection at all local times or latitudes The current study has been carried out within the frame of the International Space Science Institute (ISSI) International Team entitled ‘SO2 variability in the Venus Atmosphere’.
