On the relationship between atomic oxygen and vertical shifts between OH Meinel bands originating from different vibrational levels

Abstract

OH Meinel emissions from different vibrational levels are known to occur at slightly different altitudes in the terrestrial airglow. Earlier model studies suggested quenching by atomic oxygen to be a principal cause of these vertical shifts. Here we employ the tropical mesopause region—characterized by pronounced semiannual variations—as a natural laboratory to test the hypothesis that vertical shifts between different OH Meinel bands are a consequence of quenching by atomic oxygen. Nighttime satellite measurements of OH(3–1) and OH(6–2) volume emission rate profiles and atomic oxygen with Scanning Imaging Absorption Spectrometer for Atmospheric Chartography on Envisat are used for this purpose. Upper mesospheric atomic oxygen profiles are retrieved from measurements of the O(1S–1D) green line emission. The results demonstrate that vertical shifts between the OH bands investigated are indeed correlated with the amount of atomic oxygen in the upper mesosphere, corroborating the hypothesis.