Large amplitude perturbations in mesospheric OH Meinel and 87-Km Na lidar temperatures around the autumnal equinox

Here we report the observation of a large perturbation in mesospheric temperature that occurs shortly after the autumnal equinox in close association with the penetration of planetary-wave energy from the troposphere into the mesosphere.

This perturbation has been observed on three occasions and exhibits a departure of up to ~25-30 K from the nominal seasonal trend during a disturbed period of ~2 weeks. Such behavior represents a dramatic transient departure from the seasonal trend expected on the basis of current empirical models. These novel results coupled with a recent TIME-GCM modeling study [Liu et al., 2000] provide important insight into the role of planetary waves in mesospheric variability during the equinox periods.