HIGHLY VIBRATIONALLY EXCITED OXYGEN AS A POTENTIAL SOURCE OF OZONE IN THE UPPER-STRATOSPHERE AND MESOSPHERE

ONE of the main problems in atmospheric chemistry in recent years has been the discrepancy between theoretical model calculations of ozone concentrations and observations in the upper stratosphere and mesosphere 1. It has been suggested 2 that the photolysis of vibrationally excited oxygen could provide an extra source of ozone and new laboratory data now allows us to test this hypothesis in two ways. First, by including the proposed mechanism in a numerical model of the atmosphere, we find that the production of odd oxygen is enhanced and that the calculated ozone concentrations are significantly increased so that they agree well with observations. Second, we present a comparison between satellite observations of the daytime enhancement in the 6.9-mu-m emission from water vapour and theoretical calculations, which yields indirect evidence for the presence of vibrationally excited oxygen in the upper stratosphere and mesosphere; a significant fraction of which appears to be due to relaxation of very high vibrational levels. Both these tests demonstrate that the proposed mechanism may indeed account for most of the discrepancy between model results and observations.