J/A+A/585/A53ivo://CDS.VizieR/J/A+A/585/A53doi:10.26093/cds/vizier.35850053CDSPeralta J.Lopez-Valverde M.A.Gilli G.Piccialli A.2017-03-15T07:04:52Z2015-12-17T08:44:35ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsolar-systemsolar-system-planetsIn this work, we analysed nadir observations of atmospheric infrared emissions carried out by VIRTIS, a high-resolution spectrometer on board the European spacecraft Venus Express. We focused on the ro-vibrational band of CO2 at 4.3 microns on the dayside, whose fluorescence originates in the Venus upper mesosphere and above. This is the first time that a systematic sounding of these non-local thermodynamic equilibrium (NLTE) emissions has been carried out in Venus using this geometry. As many as 143,218 spectra have been analysed on the dayside during the period 14/05/2006 to 14/09/2009. We designed an inversion method to obtain the atmospheric temperature from these non-thermal observations, including a NLTE line-by-line forward model and a pre-computed set of spectra for a set of thermal structures and illumination conditions. Our measurements sound a broad region of the upper mesosphere and lower thermosphere of Venus ranging from 10^-2^ to 10^-5^mb (which in the Venus International Reference Atmosphere, VIRA, is approximately 100-150km during the daytime) and show a maximum around 195+/-10K in the subsolar region, decreasing with latitude and local time towards the terminator. This is in qualitative agreement with predictions by a Venus Thermospheric General Circulation Model (VTGCM) after a proper averaging of altitudes for meaningful comparisons, although our temperatures are colder than the model by about 25K throughout. We estimate a thermal gradient of about 35K between the subsolar and antisolar points when comparing r data with nightside temperatures measured at similar altitudes by SPICAV, another instrument on Venus Express (VEx). Our data show a stable temperature structure through five years of measurements, but we also found episodes of strong heating/cooling to occur in the subsolar region of less than two days.2016A&A...585A..53Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/585/A53CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/585/A53https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/585/A53http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/585/A53https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/585/A53https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/585/A53http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/585/A53GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/585/A53/table*Mean temperatures and errors with VEx/VIRTIS-H (VIRTIS-H_201510_90S-90N_06h-18h)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAltHeight range contributingkmpos.cartesian.zinte_Altrms uncertainty on Altkmstat.errorintPmaxPressure range contributing (upper value)mbarphys.pressurefloatPminPressure range contributing (lower value)mbarphys.pressuredoubleLATLatitude bin (degrees North)degpos.ecliptic.latintLON? Longitude (Not applicable)degpos.ecliptic.lonintnullableHbinLocal solar time Local Hour bin (12 is noon)htime.epochfloatTempMean atmospheric temperatureKphys.temperature;stat.meaninte_TempTemperature associated error (see paper)Kstat.errorintNspNumber of VIRTIS-H spectra or temperatures averagedmeta.numberint