TITLE:
  Vibrational temperatures and radiative cooling of the CO2 15-um 
  bands in the middle atmosphere. 

AUTHORS:
  Lopez-Puertas, M., M. A. Lopez-Valverde and F. W. Taylor


REFERENCE:
  Quart. J. Meteor. Soc., 118, 499-532, 1992



ABSTRACT:
  
Altitude and latitude distributions of the populations of the bending
and symmetric stretching vibrational levels of CO2 and of the cooling
rates induced by the bands originating from them in the middle
atmosphere (40-120 km), have been calculated for the CIRA'86 reference
atmosphere using a Non-LTE radiative transfer model. A sensitivity
study of the more uncertain parameters that strongly affect these
quantities has been undertaken. These factors are carbon dioxide and
atomic oxygen volume mixing ratios, and the rate coefficient for the
deactivation of the bending mode of CO2 by atomic oxygen. The model
includes the most recent values of these parameters: the abundances of
CO2 in the upper mesosphere and lower thermosphere as measured by, and
derived from, rocket and satellite instruments; the global
distribution of atomic oxygen density calculated by Rees and
Fuller-Rowell (1988) and the measurements of Thomas (1990); and the
fast rate for the deactivation of CO2(v2) by O3P recently derived by
Sharma and Wintersteiner (1990). Among the most important results are
the following: (i) the CO2 15-mu fundamental band is close to LTE
(Tv-Tk) up to around the 100 km level; (ii) the first and second hot
bands exhibit high vibrational temperatures, especially in the daytime
summer mesopause region; and (iii) the cooling rates by the CO2
15-mu bands in the lower thermosphere can be very large, depending on
the CO2 abundance. Finally, our results have been compared to other
recent Non-LTE models in order to quantify the effects of different
radiative transfer schemes on the calculations of vibrational
temperatures and cooling rates.