Application of Wigner distribution function for analysis of radio occultations

We present the Wigner distribution function (WDF) as an alternative to radio holographic (RH) analysis in the interpretation of radio occultation (RO) observations of the Earth's atmosphere. RH analysis is widely used in RO retrieval to isolate signal from noise and to identify atmospheric multipath. The same task is performed by WDF which also maps a 1-D wave function to 2-D time-frequency phase space and which has maxima located at the ray manifold. Unlike the standard RH technique based on the spectrum analysis in small sliding apertures, WDF is given by a global integral transform, which allows for a higher resolution. We present a tomographic derivation of the WDF and discuss its properties. Examples of analysis of simulations and COSMIC RO data show that WDF allows for a much sharper localization of the details of bending angle profiles as compared to the standard RH analysis in sliding apertures. Both WDF and RH allow for identification of multivalued bending angle profiles arising in the presence of strong horizontal gradients and may introduce a negative bias into bending angle retrieval.