Radiative heating effected by infrared CO2 bands in the middle and upper atmosphere

For the atmospheric layer between 30 and 170 Irm, the radiative heat influx in vibrational CO2 bands is refined. The refinement is based on (1) the mo st comprehensive model currently available for the system of vibrational st ates and corresponding optical transitions, (2) updated data on the rates o f vibration-translation and vibration-vibration processes, and (3) a comput ational procedure providing a high accuracy of the results. For the rate of nighttime radiative cooling, two trends are revealed. (a) A significant in crease in the rate of lower-thermosphere cooling is possible in the 15-mu m band under consideration. This increase is due to collisions between CO2 m olecules and O atoms, which are accompanied by multiquantum nu(2)-mode tran sitions. (b) The contribution of cooling in the 4.3-mu m CO2 band reaches 0 .2-0.35 degrees C/day at the stratopause. For daytime conditions, the contr ibution of each individual CO2 band between 15 and 1.05 mu m to the integra l radiative heating in CO2 bands and the dependence of this heating on the solar zenith angle are studied, The parametrization of the rate of nighttim e atmospheric radiative cooling in the 15-mu m CO2 band is improved.