The paper presents the profiles of mesospheric carbon dioxide content determined in the height range 60-90 km from the outgoing limb radiation measured in November 1994 with the CRISTA satellite instrument in the CO2 15-μm band. The satellite data are interpreted by a combined method with allowance for the effect of nonlocal thermodynamic equilibrium. This method lies in simultaneously retrieving the profiles for the kinetic temperature, pressure, carbon dioxide content, and vibrational temperatures of the lower vibrational states of the four most abundant isotopic modifications of CO2 molecules. The carbon dioxide mesospheric vertical profiles are analyzed on the basis of about 300 atmospheric scans (all radiation spectra measured in the range from the minimum to the maximum tangent height) measured over the latitude belt 50° S-65° N. It is shown that a decrease in the carbon dioxide volume mixing ratio with height begins, on the average, at a height of 70-75 km. This height is significantly lower than that predicted from numerical models of the upper atmosphere. However, this result is in complete agreement with the carbon dioxide retrieval data obtained from the CRISTA instrument measurements on the basis of a distinctly different approach, which is based on radiation measurements in the 4.3-μm band and numerical simulation of the nonequilibrium populations of CO2 vibrational states. This agreement indicates that our results are highly reliable. However, some events of CO2 uniform mixing up to a height of about 85 km were also revealed. The mean profiles of the carbon dioxide volume mixing ratio measured for the middle latitudes of both hemispheres differ from each other at a height of 90 km by no more than 40 ppmv. The mean latitude gradients of the CO2 volume mixing ratio in the middle and upper mesosphere reach 4.8 ppmv per 10°. The CO2 concentration decreases from southern (spring) toward northern latitudes (fall).
|Number of pages||11|
|Journal||Izvestiya - Atmospheric and Ocean Physics|
|State||Published - 1 May 2003|
Scopus subject areas
- Atmospheric Science