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 HF and 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 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. (3) The Es intensity positively correlates with the terrain. Es intensity in the southeast is higher than northwest of the Plateau significantly.

The interest in the use of spaceborne synthetic aperture radar (SAR) for collecting earth bio/geophysical information and detecting foliage-obscured targets has been increased. However, the signals are inevitably affected by the ionosphere, particularly at very high frequency and ultrahigh frequency. Thus, it is crucial to understand the potential effects of the ionosphere on SAR systems. In this paper, three possible contributions are made to analyze these effects. First, for analyzing range resolution, in addition to linear and quadratic phase errors due to the background ionosphere, the cubic phase error is considered. The expected mean electron density inferred from the International Reference Ionosphere is used. Second, for analyzing azimuthal resolution, the effects of ionospheric irregularities are evaluated under the conditions of oblique incidence and anisotropic irregularities. The model is presented on the basis of the multiple phase screen (MPS) method. Compared with the previous model, the MPS method can give results in good agreement with both weak and strong scattering theories. Finally, based on the theory of moment equation, range resolution degradation caused by the multiple scattering is also studied in the case of anisotropic irregularities. By using the range Doppler algorithm, a number of degraded point responses due to these ionospheric effects are shown, and then, some evaluation results are listed.