Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) observations of tracer transport by inertially unstable circulations

The first mission of the Cryogenic Infrared Spectrometers and Telescopes fo r the Atmosphere (CRISTA) instrument obtained 7 days of nearly continuous h igh-resolution global data in the stratosphere and mesosphere during Novemb er 1994. During the later part of the mission, the temperature data near th e equatorial stratopause have stacked perturbations with short (similar to 10 km) vertical scales. These type of structures have been identified in pr evious studies arid are consistent with a low-latitude circulation respondi ng to inertial instability. The disturbances seen in CRISTA temperatures ha ve, in common with previous measurements, paired perturbations of opposite sign near the equator and in the subtropics of the winter hemisphere, a hor izontal location coincident with conditions of inertial instability, and th e simultaneous extension of a planetary wave from midlatitudes into the equ atorial region. The amplitude in the present case is smaller than previousl y documented. Concentrations of two trace species in the upper stratosphere (ozone and methane) show perturbations consistent with the predicted respo nse to an inertially unstable circulation, either through transport (methan e) or photochemical changes (ozone). A new finding is that the upper strato spheric dynamical features appear to be linked to a tropical Kelvin wave in the lower stratosphere. Motions associated with the Kelvin wave may affect or control the vertical scale of the unstable circulation cell that gives rise to the stacked temperature perturbations.