Studies On Atmospheric Refractivity Profile Model And Radio Wave Refractive Error Correction Method

The time delay and path bending of the radio wave propagation, caused by atmospheric refraction, is one of the key restricting factors in improving the precision of radio wave orientation and velocity measurement systems. Apparently, the atmospheric refractivity profile model and radio wave refractive error correction method should be further studied, and some new results are developed in this thesis by using the local radiosonde data, in which the main achievements are as follows:Several existing meteorologic models have been compared using the historical radiosonde data in Qingdao and Beijing from 1986 to 1995, and the results show that the Hopfield refractivity profile model has the best agreement with the actual refractivity profiles of troposphere.Based upon the Hopfield refractivity profile model, the new models are developed, where the temperature lapse rateβand the empirical constantλ—partial pressure of water vapor and the total air pressure, are regressed by using the radiosonde data in Qingdao and Beijing. The regression relations between the parameters in the model and the surface temperature are employed in the new models. The analysis with historical radiosonde data shows that the new model obtain better prediction precision of the refractivity profile than the old ones.Using the newly established refractivity profile model, four typically examples in spring, summer, autumn, and winter are selected, and their range and elevation angle errors are analysed by using ray tracing method, in which it is shown that the bending error can not be ignored when the elevation angle is below 5°, especially in the high precision measure system. Besides, the trend of refractive error along with variety of elevation angle at lower elevation angles are different from that at higher ones. Based on the above analysis and using the historical radiosonde data in Qingdao, semi-empirical refraction correction methods are established, which respectively adapt to lower and higher elevation angle. Its validity is also verified by using the experimental measurement data from Xi'an Satellite Control Centre, in which the new method can obtain good agreement with the ray tracing method, and it is better than the ITU-R(International Telecommunication Union-Radiocommunication) method at lower elevation angle.