Surface refractive index field estimation from multiple radars

Abstract

Retrieval of surface layer refractivity via the method of Fabry et al. (1997) is considered. A mathematical framework is constructed, and signal processing algorithms are derived that facilitate refractivity retrieval from the returns from multiple radars viewing a common geographical area. In particular, an approximate discrete model is derived to relate the measured phases to the surface layer refractivity fields, and a modified least squares estimation algorithm is then proposed for the resulting, often ill‐conditioned, inversion problem. Because the measurement technique is subject to modulo 2π uncertainties which impact retrievals, a novel algorithm which jointly estimates the unwrapped phases and refractive index (RI) field is also provided. Numerical results indicate the effectiveness of the derived algorithms in both the single‐ and multiple‐radar cases, as well as clearly establishing that having multiple views of the same geographical area from separate radars provides for significant improvement of the RI field estimates.