Lidar Observations of the Upper Atmospheric Nickel Layer at Beijing (40∘N,116∘E)

Ni atoms, produced in the Earth's upper atmosphere by meteoric ablation, are challenging to measure by lidar because the Ni atom density is low, the resonance scattering cross section is relatively small, and the transitions occur in the near-UV around 340 nm where absorption by the stratospheric ozone layer starts to become significant. A new Ni lidar has been designed and deployed at Yanqing station (40∘N,116∘E) Beijing, China over the period from 3 April 2019 to 31 December 2019. The combination of a frequency-doubled near-IR laser and narrow bandwidth filters enables stable and continuous operation. From 25 nights of measurements, the Ni peak density ranges from 98 to 460 cm−3 with the peak altitude between 80 and 88 km; the average peak density is 258±115cm−3. The average column abundances of Nickel varied between 1.52×108 and 6.0×108 cm−2 between mid-summer and mid-winter. An experiment was also carried out using the Ni lidar to determine the spectroscopic branching ratios from the excited Ni(3F4) state into 3 lower states; very close agreement with the literature values were obtained.