Horizontal temperature at Venus upper atmosphere

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.