New winds and temperature observations across turbopause (~100-120 km) by the upgraded Na lidar at Utah State University.

Abstract:

The atmosphere across the turbopause (100 km ~ 120 km) plays critical role in various dynamic and ion-neutral coupling processes in the upper atmosphere, while it is also the least explored the region in the atmosphere. Except for some instantaneous rocket measurements, this part of the atmosphere is inaccessible for most of the remote sensing instruments. Recently, when utilizing ~ 5 m² Rayleigh lidar receiver, a Na temperature/wind lidar at Utah State University are able to extend its range of temperature and wind measurements up to ~ 120 km consistently during summer. These new measurements have revealed long lasting vertical wind perturbations (as much as more than 15 m/s) across turbopause region, even when the lidar data are binned hourly to smooth out the small-scale short period perturbations. Although such large vertical wind perturbations have been reported in high latitude region, most likely due to strong geomagnetic activities there, this is the first report on such feature in middle latitude during geomagnetic quiet time. This unique feature is quite distinct to those in the mesosphere where the magnitude of these perturbations are close to zero, implicating dramatic change of neutral atmosphere across turbopause. The simultaneous temperature observations also indicate considerable temperature perturbations. In this paper, we report these new Na lidar observations in the lower thermosphere during the summer of 2018 and 2020, and try to understand the mechanism and its implication to the lower thermosphere dynamics.