GPS无线电掩星后向传播方法

在大气多路径传播条件下,讨论了两种无线电信号的反演方法:几何光学方法和后向传播方法.当大气存在多路径效应时,采用几何光学方法反演大气参数会引入较大误差.后向传播方法将无线电信号从多路径区域反推至单路径区域,减少了大气多路径效应的影响.为了比较不同的反演方法,利用多相位屏模型,数值模拟了大气多路径条件下无线电信号在大气中...

Back propagation method for GPS radio occultation data

For determination of bending angle profiles from radio occultation in multipath areas, two methods, i.e., the geometric optics (GO) method and back propagation (BP) method, are compared and discussed. The GO method does not work well in multipath areas while in the BP method electromagnetic field can be back-propagated from multipath area to a single-ray area for reducing multipath effects. The atmospheric propagation of GPS signals under multipath conditions and their detection are simulated by using multiple-phase-screen model. Under the assumption of ideal signal, bending angles computed by the GO method and BP method are compared with corresponding solutions to Abel integral (true), the results reflect that the BP method is much closer to Abel integral in multipath area. About 15000 CHAMP radio occultations from March to July in 2007 are retrieved by the GO method and BP method, statistical comparisons of the retrieval refractivity profiles with that of ECMWF show that the average deviation and variance of fractional difference in refractivity retrieved by the BP method are generally smaller than that by the GO method in the lower troposphere of the southern hemisphere (30°S ~ 90°S), the tropics (30°S ~ 30°N), as well as the northern hemisphere (30°N ~ 90°N). The results confirm that the BP method can solve the problem of calculating bending angle profiles within multipath regions better than the GO method.