Lidar Exploration of Vertically Stratified Na Layers from 75 to 150 km
The region spanning the mesosphere, thermosphere, and ionosphere is a critical interface for the exchange of mass, energy, and momentum between Earth’s atmosphere and near-Earth space, yet it remains challenging to observe continuously. High-sensitivity resonance-fluorescence lidar provides a unique means of observing meteoric metal layers and investigating ion–neutral coupling processes across this region.
This talk presents results from 7 years of Na Doppler lidar observations collected over Boulder, Colorado, from 2011 to 2017. The observations reveal the regular occurrence of thermosphere-ionosphere Na (TINa) layers with coherent downward phase progression, as well as systematic nocturnal and seasonal variations. A year-round climatology extending from 75 to 150 km further reveals distinct annual and semiannual oscillations (AO & SAO) in Na density and volume mixing ratio across different altitude regimes.
A central finding of this work is that meteoric Na layers are vertically stratified into three related but distinct altitude regimes: the main Na layer (75–105 km), the Na transition layer (95–120 km), and the TINa layer (110–150 km). By combining high-sensitivity lidar observations with volume mixing ratio and normalized Na-density analyses, this research reveals the vertical structures, distinct temporal evolution, and seasonal variability of these layers across the 75–150 km region. Comparisons with modeled atmospheric tides, neutral winds, and WACCM-X-Na simulations further suggest that this vertical stratification reflects the changing roles of neutral transport, metallic-ion convergence, and ion-neutral chemistry with altitude.
These results establish lidar observations as a powerful means of resolving vertically stratified Na layers across the mesosphere, thermosphere, and ionosphere. By revealing how the main Na layer, transition layer, and TINa layer are organized and evolve together, this work provides new observational constraints on vertical transport and dynamical and chemical coupling in the coupled ionosphere-thermosphere-mesosphere (ITM) system.
Yingfei Chen recently earned his Ph.D. in Aerospace Engineering Sciences from the University of Colorado Boulder in August. He received his B.S. in 2019 from Wuhan University in China and his M.S. in 2021 from the Georgia Institute of Technology. His research focuses on high-sensitivity resonance-fluorescence lidar observations of meteoric metal layers, particularly thermosphere-ionosphere Na (TINa) layers, to investigate atmospheric dynamics and coupling processes in the mesosphere, thermosphere, and ionosphere.