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 for the Atmosphere (CRISTA) instrument obtained 7 days of nearly continuous high-resolution global data in the stratosphere and mesosphere during November 1994. During the later part of the mission, the temperature data near the equatorial stratopause have stacked perturbations with short (∼10 km) vertical scales. These type of structures have been identified in previous studies and are consistent with a low-latitude circulation responding to inertial instability. The disturbances seen in CRISTA temperatures have, in common with previous measurements, paired perturbations of opposite sign near the equator and in the subtropics of the winter hemisphere, a horizontal location coincident with conditions of inertial instability, and the simultaneous extension of a planetary wave from midlatitudes into the equatorial region. The amplitude in the present case is smaller than previously documented. Concentrations of two trace species in the upper stratosphere (ozone and methane) show perturbations consistent with the predicted response to an inertially unstable circulation, either through transport (methane) or photochemical changes (ozone). A new finding is that the upper stratospheric 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.