Characteristics of Sporadic E Layer Over and Around Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau (QTP) is located at the roof of the world. Since its unique geography, the spatial-temporal characteristics of sporadic E layer (Es) over and around there could be hints of the coupling between upper and lower atmosphere. It also plays an important role on radio propagation at high frequency (HF) and very HF (VHF) band. In this letter, the intensity and spatial distribution of Es over the QTP, and the response to solar activity are studied. With the bonus of the Chinese ionosonde network for more than 60 years, some conclusions are arrived at firstly for the QTP: 1) the diurnal and seasonal variations of Es layer are significant. The intensity and critical frequency are the highest at 11:00 and 12:00 local time (LT) in summer, while the lowest at sunrise in winter; 2) it is found that the Es intensity is negatively correlated with the solar cycle. In 2020, the solar minimum of 200 years, Es intensity is obvious higher than other years; and 3) the Es intensity positively correlates with the terrain. Es intensity in the southeast is higher than northwest of the Plateau significantly.