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J/A+A/585/A53  Horizontal temperature at Venus upper atmosphere (Peralta+, 2016)

Dayside temperatures in the Venus upper atmosphere from Venus Express/VIRTIS nadir measurements at 4.3µm. Peralta J., Lopez-Valverde M.A., Gilli G., Piccialli A. <Astron. Astrophys. 585, A53 (2016)> =2016A&A...585A..53P (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Planets Keywords: molecular processes - radiation mechanisms: non-thermal - radiative transfer - instrumentation: spectrographs - methods: data analysis - planets and satellites: atmospheres Abstract: In 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 10-5mb (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. Description: The dayside atmospheric temperatures in the UMLT of Venus (displayed in Figure 7A of this article) are listed as a CSV data file. These values consist of averages in bins of 5° in latitude and 0.25-hours in local time from dayside temperatures covering five years of data (from 2006/05/14 to 2011/06/05). These temperatures were inferred from the CO2 NLTE nadir spectra measured by the instrument VIRTIS-H onboard Venus Express (see article for full description of the procedure), and are representative of the atmospheric region between 10^-2 to 10^-5mb. Along with the temperatures, we also provide the corresponding error and the number of temperatures averaged in each bin. The format of the CSV file reasonably agrees with the expected format of the data files to be provided in the future version of the Venus International Reference Atmosphere (VIRA). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table.dat 59 1314 *Mean temperatures and errors with VEx/VIRTIS-H (VIRTIS-H20151090S-90N_06h-18h)
Note on table.dat: Observation date : 2006-134/2011-156. Longitude not Applicable (zonal averages are done in Local Time) FOV<10km. Planet radius = 6051.8km.
Byte-by-byte Description of file (# headlines): table.dat
Bytes Format Units Label Explanations
1- 14 A14 --- --- Date (Not applicable) 16- 18 I3 km Alt Height range contributing 20- 21 I2 km e_Alt rms uncertainty on Alt 23- 26 F4.2 mbar Pmax Pressure range contributing (upper value) 28- 33 E6.3 mbar Pmin Pressure range contributing (lower value) 35- 37 I3 deg LAT Latitude bin (degrees North) 39- 41 I3 deg LON ?=- Longitude (Not applicable) 43- 47 F5.2 h Hbin Local solar time Local Hour bin (12 is noon) 49- 51 I3 K Temp Mean atmospheric temperature 53- 54 I2 K e_Temp Temperature associated error (see paper) 56- 59 I4 --- Nsp Number of VIRTIS-H spectra or temperatures averaged
Acknowledgements: Javier Peralta, javier.peralta(at) History: * 17-Dec-2015: on-line version * 03-Mar-2017: correct table with all lines and header
(End) Javier Peralta [ISAS/JAXA, Japan], Patricia Vannier [CDS] 09-Nov-2015
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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