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Observations of thermospheric NO and kinetic temperature from 5.3 um emission measured by MIPAS on Envisat

Diego Bermejo-Pantaleón(1), Bernd Funke(1), Manuel López-Puertas(1), Maya García-Comas(1), Thomas von Clarmann(2), Gabriele Stiller(2), Udo Grabowski(2) and Norbert Glatthor(2)

(1) Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 50, 18008 GRANADA, Spain
(2) Institut für Meteorologie und Klimaforschung, FZK, Hermann-von-Helmholtz-Platz 1, 76021 Karlsruhe, Germany


Nitric oxide is an important species in the upper mesosphere and lower thermosphere for several reasons: first, due to its permanent dipole moment it acts as a strong radiative cooler; second, it is transported downwards into the mesosphere and stratosphere during polar night, participating in the catalytic destruction of ozone; third, the rotational structure of its emission spectrum can be used to determine kinetic temperature in the thermosphere; and fourth, its low ionization potential makes NO an important source of ionization in D and E regions in the ionosphere at all latitudes.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board Envisat (ESA) observes regularly the upper atmosphere up to 170 km, providing rotationally resolved 5.3 um emission from the NO fundamental band. These emissions have been used to retrieve simultaneously thermospheric NO abundances and kinetic temperature. As NO emission is affected by vibrational non-LTE above the troposphere and by rotational/spin non-LTE in the thermosphere, the non-LTE algorithm GRANADA is coupled into the inversion scheme in order to constrain vibrational, rotational and spin populations of NO.

In this paper, we present first results of retrieved kinetic temperatures and nitric oxide volume mixing ratio in the thermosphere (110-160 km) and compare to model results. Further, we describe and characterize the thermospheric NO and kinetic temperature retrieval, paying particular attention to its sensitivity to non-LTE-related uncertainties.