Morphology of nighttime ion, potassium and sodium layers in the meteor zone above Arecibo

We use over ten years' incoherent scatter radar (ISR) data and several years of potassium and sodium resonance lidar data to study the morphologies of ion, potassium, and sodium layering activities in the mesopause region above Arecibo, Puerto Rico. A tidal effect is clearly seen in the layer trajectories of all three species. Semidiurnal ion layer tidal structure is observed in the spring, summer, and fall at above 105 km altitude. Below 100 km altitude, the most consistent ion layers occur at 95 km altitude at 1800 local time (LT) during most time of the year except in the summer. The strongest ion layers occur around sunset hours at 106 km altitude in the summer. Although both potassium and sodium are alkaline metals, their layers exhibit very different characteristics. Throughout the mesopause region, sodium layer trajectories are always downward throughout the year, in response to the diurnal tide in this region. The tidal effect on the potassium layers can be seen mostly in the 90-95 km altitude region. While the mesopause height does not appear to be related to the seasonal variations of the potassium layers centroid height, it does appear to have great influence on that of the sodium layers. The potassium layer abundance is highest in the summer and a secondary peak occurs in the winter. The semiannual variation of the potassium layer abundance may provide an important clue to a better understanding of the potassium chemistry.