The radio propagation affected by variation of refractive index

Affected by the medium, radio wave shows different characteristics when transmitting in space. All of the earth-space transmitting are influenced by the unionized atmosphere (especially troposphere) for its large density, high humidity, violently changed temperature and humidity, which can be seen from refractive index. By analyzing the radiosonde data from Wuhan (30.5°N, 114.4°E) weather bureau, we find out the variation of the tropospheric refractive index, which reached the extremum in summer and winter. There also exist a weaker difference between the morning and the evening. The gradient of refractive index showed similar variation and the visual distance violently changed with refractive index, especially when the elevation angle is lesser.