Daytime Lidar Measurements of Na Density and Temperature in the MLT at McMurdo, Antarctica

For more than a decade, the ongoing McMurdo lidar campaign in Antarctica has produced numerous discoveries and results on topics such as gravity waves and thermospheric metal layers. These results primarily stem from Fe and Na lidar data collected at night, when low background noise allows high-fidelity temperature, wind, and species density measurements. However, the McMurdo lidar systems are also capable of daytime operation, and the retrieval of temperature, wind, and density measurements from daytime Na lidar data is highly desirable to extend the scientific scope of the McMurdo lidar campaign.

Daylight Na measurements are realized through the use of a Faraday anomalous dispersion optical filter (FADOF), which strongly attenuates background noise outside of a narrow passband centered on the D2a peak. The FADOF’s narrow passband results in frequency dependent receiver filtering, which needs to be compensated to accurately extract temperature, radial wind, and Na density from raw photon counts. Through consideration of this and other factors, this work aims to retrieve temperature and species density from daytime Na lidar measurements at McMurdo. These results will be compared to simultaneous Fe lidar observations to examine similarities and differences in MLT metal layer densities/mixing ratios and behaviors.