Two Methods for Sounding the Wet Refractivity Profile by GPS

The water vapor in the atmosphere plays a very important role on the variation of the atmospheric refractivity, which has a great influence on the applications of remote sensing. During recent years, new techniques have been developed to retrieve the water vapor by global positioning systems (GPS). This paper uses tomographic and downward looking radio occultation (RO) methods to retrieve the wet refractivity profile. Results from both approaches are compared with the radiosonde. It suggests that the RO method can recover the wet refractivity profile with a much higher vertical resolution, but a smaller coverage in height, compared with the tomographic method. Profiles from both methods agree well with a similar accuracy of 5-7 N (refractivity unit) when compared with the observation from the radiosonde. The two approaches complement each other in water vapor profiling, which gives great potential for the application to meteorology and remote sensing.