Comparative Study of the Es Layer between the Plateau and Plain Regions in China

The lower atmosphere forcing plays an important role in forming the sporadic E (Es) layer in the ionosphere. In this study, a comparative study of the Es layer recorded by ionosondes at the middle latitude regions was carried out between the plateau and plain regions in China. The two ionosonde stations (Zhangye, 39.21°N, 100.54°E and Beijing, 40.25°N, 116.25°E) are located at the Qinghai–Tibet Plateau and North China Plain, respectively. The data during the year 2018 were used to reveal the characteristics of the Es layer. The occurrence probability, the critical frequency (foEs) and the base virtual height (h’Es) were considered in this study. Results show that: (1) The diurnal and seasonal variations of the occurrence probability between these two regions are similar. The maximum occurrence probability is at noontime and in the summer season. However, the Es at Zhangye occurred more frequently than Beijing at nighttime and in winter to early spring. (2) Similar to previous studies, the maximum value of foEs at Beijing mainly occurred in summer. Interestingly, the maximum value is in winter at Zhangye station. (3) The characteristics of the anomaly of the Es layer at Zhangye are mostly consistent with the characteristics of atmospheric gravity waves in the Qinghai–Tibet Plateau. Therefore, compared with observations at Beijing, the anomalies of the Es layer at Zhangye (at night and in winter to spring) might be attributed to gravity waves in the lower atmosphere over the Qinghai–Tibet Plateau.