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A new MesosphEO dataset of temperature profiles from 35 to 85 km using Rayleigh scattering at limb from GOMOS/ENVISAT daytime observations

Abstract : Given that the scattering of sunlight by the Earth's atmosphere above 30–35km is primarily due to molecular Rayleigh scattering, the intensity of scattered photons can be assumed to be directly proportional to the atmospheric density. From the measured relative density profile it is possible to retrieve an absolute temperature profile by assuming local hydrostatic equilibrium, the perfect gas law, and an a priori temperature from a climatological model at the top of the atmosphere. This technique is applied to Rayleigh lidar observations for over 35 years. The GOMOS star occultation spectrometer included spectral channels to observe daytime limb scattered sunlight close to the star direction. GOMOS Rayleigh scattering profiles in the spectral range 420–480nm have been used to retrieve temperature profiles in the altitude range 35–85km with a 2-km vertical resolution. A database of more than 309,000 temperature profiles has been created. A global climatology was built and compared to GOMOS external model. In the upper stratosphere, where the external model is based on ECMWF analysis, the agreement is better than 2K. In the mesosphere, where the external model follows MSIS climatology, 5 to 10K differences are observed. Comparison with nighttime collocated Rayleigh lidar profiles above south of France shows some differences with a vertical structure that may be at least partially explained by the contribution of thermal diurnal tide. The temperature evolution obtained at Equator indicates the occurrence of mesospheric inversion layers in the temperature profile with global longitudinal extension, descending in about one month from 80 to 70km. The climatology shows a semi-annual variation in the upper stratosphere, a stratopause altitude varying between 47 and 54km and an annual variation in the mesosphere. The technique to derive temperature profiles from Rayleigh scattering at limb can be applied to any other limb-scatter sounder providing observation in the spectral range 350–500nm. This is also a good candidate for a future small satellite constellation due to the simplicity of the principle.
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Submitted on : Monday, August 6, 2018 - 8:11:59 PM
Last modification on : Saturday, September 19, 2020 - 4:39:21 AM

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Alain Hauchecorne, Laurent Blanot, Robin Wing, Philippe Keckhut, Sergey Khaykin, et al.. A new MesosphEO dataset of temperature profiles from 35 to 85 km using Rayleigh scattering at limb from GOMOS/ENVISAT daytime observations. Atmospheric Measurement Techniques Discussions, 2018, pp.(Under Review). ⟨10.5194/amt-2018-241⟩. ⟨insu-01854617⟩



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