IAA authors:
López-Puertas M.;Koukouli M.E.;Funke B.;Gil-López S.
Authors:
López-Puertas M., Koukouli M.E., Funke B., Gil-López S., Glatthor N., Grabowski U., von Clarmann T., Stiller G.P.
Journal:
Geophysical Research Letters
Abstract:
We present unequivocal evidence for CH4 7.6 μm non-local thermodynamic equilibrium (non-LTE) mesospheric emissions as measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) experiment on board the ESA Envisat satellite. We have employed non-LTE radiative transfer models, already used and validated in studies of other atmospheric gases, in order to quantify the magnitude and extent of the CH4 non-LTE deviation in the Earth's atmosphere. The observed daytime enhancement signatures apparent in the measured radiances cannot be attributed to enhanced daytime temperatures and/or CH4 abundance variations and are reproduced successfully with a dedicated CH4 non-LTE radiative transfer model. We conclude that depending on the upper stratospheric/mesospheric temperature structure, the departure from LTE might commence at an altitude as low as 45 km, reaching limb radiance deviations of 20% at 60 km and quickly rising up to 60% at 70 km, for the 7.6 μm CH4 lines. Copyright 2005 by the American Geophysical Union.
URL:
https://ui.adsabs.harvard.edu/#abs/2005GeoRL..32.4805L/abstract