(A) study on the characteristics of radio duct propagation in Korean coastal region

Abstract

This dissertation proposes simple methods to estimate an abnormal radio wave propagation, which can transmit electromagnetic energy with almost no propagation loss, using easily obtainable surface meteorological data. The proposed estimation methods were verified by analyzing the relationships between various individual meteorological parameters and their gradients; for example, the relationship between the monthly refractivity gradient and the monthly surface refractivity, that between the monthly surface refractivity and the individual monthly meteorological parameter, etc. Radio wave propagation around the earth is determined by the refractive index structure of the atmosphere through which the radio wave travels. Thus, fully understanding of the refractive index structure within the radio path is of fundamental importance in studying radio wave propagation. One of the most important factors affecting radio wave propagation is the vertical refractivity gradient and its statistical characteristics. In this study, the radiosonde datasets were collected and analyzed to establish the statistical characteristics of vertical refractivity and atmospheric parameters in Korea. The analysis results show that the formation of a radio duct $(\It{N^{``}} <-157 N/km or \It{M^{``}} < 0 M/km)$ strongly depends on the variations in humidity, and a radio duct can be formed at temperatures in excess of $-5.1\degC$ which agrees with the measurement results rather well $(-4.4\degC)$. However, radiosonde data is usually coarse because it is collected at a fixed position and only twice daily; hence it does not accurately represent the meteorological characteristics. On the other hand, surface meteorological parameters such as surface refractivity, temperature, humidity, and pressure can be obtained more easily from the ground weather stations. Therefore if the correlation between the refractivity gradient and surface refractivity can be established, the refractivity gradient...