Special Structures Of Mid-upper Atmospheric Metal Layers And Their Formation Mechanisms Based On Fluorescence Lidar

The study of atmospheric metal layers have made a lot of progress after decades of development, but there are still many problems need to be resolved. Under the premise of atmospheric ions changing into metal atoms, how do we accurately extract kinetics parameters from the change of atmospheric of metal layers? How do the atmospheric sporadic metal atoms(Ns) form? We do not know whether there is a metal source and what is the corresponding trigger mechanism of Ns in the high altitude. Although the mechanism of Es metal ions converting to atomic proposed by Plane has been increasingly dominant, not all of the sodium atoms are formed entirely by the phenomenon of Es. What the specific chemical processes of atmospheric metal atom and ions are? How much the corresponding chemical reaction coefficient is? It has very important significance for the accurate estimate of the chemical reaction process and the model simulation. From the probe point of view, the sodium lidars are maily used both at home and abroad, only existing a small number of iron, potassium and calcium lidar, and these lidars rarely do routine observation, so the probe means are so single, not providing sufficient data for scientific explorations, severely limiting the study of atmospheric metal layer and the upper atmosphere.This paper describes individual characteristics of sporadic sodium layers(Nas) at three sites near 120°E meridian chain. From higher to lower latitudes, the occurrence rate of sporadic sodium layer at each station are 1 event/17 h(Beijing 40.2°N), 1 event /8 h(Wuhan 30.5°N) and 1 event/5 h(Haikou 19.5°N), respectively. The average occurrence of the sporadic sodium layers exhibit increasing trend with the decreasing latitude. The mean peak height of sporadic sodium layers at Beijing and Haikou is about 95 km, about 2 km higher than that at Wuhan; full width at half maximum(FWHM) of the sporadic sodium layer is more narrow with decreasing latitude; the distribution of strength factors at each station showed similar trends; the average duration of sporadic sodium layers at Haikou is the longest one. Night distribution trends of the occurrence of sporadic sodium layers are different in every season. Typically, the occurrence of sporadic sodium layers at each station was relatively large in the summer months. But at Haikou, sporadic sodium layer does not exhibit such a sudden change of seasons, its maximal rate occurred at 1-2 months. At Beijing and Wuhan, sporadic sodium layers and sporadic E layer had good seasonal correlation, but the correlation at Haikou was poorer, the average occurrence of sporadic E layer was higher than that at other two sites. The relationship between sporadic E layer and atmospheric wind indicated that the formation of low-latitude sporadic sodium layers is also affected by the tidal wind and wind shear. Mechanism of low latitude sporadic sodium layer is worth exploring deeply.Based on the upgrading Na-K lidar at Yanqing, Beijing, we first explored in detail some of the basic properties of sporadic potassium layers(Ks), and made a comparison of potassium and sodium layers at Beijing. We selected data sounding sodium and potassium layer from May 2013 to April 2014 and from November 2010 to December 2011. The average occurrence of sporadic potassium layer was about 2.9 % and that of sporadic sodium layer are about 5.9 %. Ks and Nas presented completely different seasonal variations. The maximal ccurrence of sporadic sodium layer located at 6-7 months, the minimum in 1-2 months. But the maximal rate of sporadic potassium layer occured in 1-2 months. The seasonal variation of sporadic sodium layer was similar with other mid-latitude observatories. However, seasonal variation of Nas was not only different with Ks, but also different with the Arecibo station observed trends of Ks. Most Ks peak heights were located at about 93 km, which was about 2 km lower than that of Nas. The mean FWHM of Ks was 0.9 km, which was narrower than that of Nas(1.7 km). The mean strength factor of Ks was also slightly larger than Nas; the duration of Ks and Nas events are similar. However, the Ks asending time was longer than its descending time, Nas showed opposite situation. Ks average peak density was about 1/10 of Nas, but there were two high density of Ks events(> 1000 cm-3), which can be compared with the magnitude of sodium layer, previous report showed that K density was in the range of 15-300 cm-3, so it is the first time observing such great potassium layer density. In the examples of sporadic potassium and sodium layer simultaneously appeared, potassium layer tend to take longer time to reach the greatest peak density. The characteristics of potassium and sodium layer layer will facilitate studies of mechanism of the metal layer.The sporadic sodium layers at Haikou had its own peculiarities. Based on about two years of observation lidar data at Haikou, we found six C-Nas events. These events had weak correlation with Es, wave breaking and KH instability. C-Nas was closely related with atmospheric wind: firstly, there is an increased density of sodium cloud, with horizontal scale of about 50 km and the vertical height range of about 10 km, then wind shear disturbance affected on the sodium cloud, so the C-type structure appeared on lidar height-time plots.