Lidar Observations of Thermosphere-Ionosphere Na (TINa) Layers at two nearby stations in North China

The metal layers in the Earth’s upper atmosphere have received growing attention in recent years because of the discovery of the Thermosphere-Ionosphere metal (TIMt) Layers by lidar. In the reports of lidar detection TIMt Layers, the highest metal atom layer is Thermosphere-Ionosphere Na (TINa) Layers observed at Yanqing station (40.42°N, 116.02°E, Xun et al., 2019), while the Ca+ Ions Transport From ∼80 to 300 km were also observed at Yanqing station (Jiao et al., 2022). According to their morphological characteristics and occurrence frequency, and referring to the previous reports, the TINa layers observed at mid-latitude can be mainly classified into the following four types: lower thermosphere sporadic Na layers, dawn thermosphere-ionosphere Na layers, midnight thermosphere-ionosphere Na layers and mid-latitude thermosphere-ionosphere Na layers (Mid-TINa). Moreover, there are rare reports of the small scale horizontal distributions of TiNa layers. In 2014, another Na lidar was developed at Pingquan station(41.0°N, 118.7°E), which is about 250 km away from Yanqing station. By analysis data of these two lidar, the occurrence frequency, distribution, and morphological characteristics of four types TINa layers are studied.