大气折射对我国近地面无线电视距的影响分析

在无线电视距工程应用中, 常用等效地球半径因子表征大气折射的影响.为深入分析我国不同区域大气折射对无线电视距的影响, 定义了一种无线电视距因子, 以表征无线电视距相对标准大气视距的变化.基于我国区域近地面65 m高度大气折射率梯度数据, 得到了不同时间概率下我国区域无线电视距因子的时空分布, 结合拉萨、重庆、厦门、渤海湾、西沙、乌鲁木齐典型地区无线电视距因子的时间概率分布和季节变化, 分析给出了我国区域无线电视距因子的时空分布特征.分析结果表明, 我国不同地域无线电视距存在显著的时空变化, 并可导致无线电系统最大覆盖区域的显著时空变化.这些结果可为我国不同区域无线电系统设计和覆盖性能评估等提供参考依据.

Effects of the atmospheric refraction on radio line-of-sight distance near the ground in China

In the engineering applications of radio line-of-sight distance, the effective earth radius factor is usually used to characterize the influence of the atmospheric refraction on radio wave propagation. For deeply analyzing the impact of the atmospheric refraction on radio line-of-sight propagation in different regions of China, a radio horizon distance factor is defined in this paper, which can be utilized to characterize the variations of the radio line-of-sight distance relative to the one of standard atmosphere. Based on the atmospheric refractivity gradient data in the lowest 65 m near the ground in China, the statistics of the radio line-of-sight distance factor are obtained in China with the annual and monthly values exceeded for different percentages of time, the characteristics of temporal and spatial variations are analyzed with the data mentioned above and interpolated in the typical area such as Lasa, Chongqing, Xiamen, Bohai Gulf, Xisha and Urumqi. The results show that there are significant temporal and spatial variations of the radio horizon distance factor in different areas of China, which may cause significant temporal and spatial variations of the coverage performance of radio systems. The results are very important for the design and coverage performance evaluation of radio systems used in different areas of China.