Middle atmosphere Kelvin waves observed in cryogenic infrared spectrometers and telescopes for the atmosphere (CRISTA) 1 and 2 temperature and trace species

Abstract

A number of tropical perturbations that have all the characteristics of Kelvin waves are identified in temperature measurements from the two flights of the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument. The background wind conditions during the two flights were quite different due to the different phases of the quasi-biennial oscillation (QBO), and there were differences in the Kelvin waves observed. During each flight, there were several different zonal wave numbers and/or frequencies present simultaneously. The observed waves conform well to theory. In particular, lower-frequency waves are confined to the lower stratosphere, while higherfrequency waves appear in the upper stratosphere and mesosphere; the waves are centered on the equator; and the frequency and structure satisfy the dispersion relation. Wave signals also appear in several stratospheric trace species: O3, CFC-11 (CFCl3), HNO3, N2O, and CH4. The sense of the correlation of these trace species perturbations with temperature (negative for CFC-11, N2O, and CH4; positive for lower stratospheric HNO3 and O3) confirms that vertical velocity is responsible for the perturbations. There is a shift in the relative phases as photochemical processes become more important with increasing altitude. Upper stratospheric ozone correlates negatively with temperature due to temperature-dependent reaction rates that destroy ozone.