Improving radar refractivity retrieval by considering the change in the refractivity profile and the varying altitudes of ground targets

However, the technique as originally developed makes some simplistic assumptions about the heights of ground targets (HT) and the vertical gradient of refractivity (dN/dH). In reality, the field of target phases used for refractivity retrieval is noisy because of varying terrain and introduces estimation biases.

To obtain a refractivity map at a constant height above terrain, a 2D horizontal refractivity field at the radar height must be computed and corrected for altitude using an average dN/dH. This is achieved by theoretically clarifying the interpretation of the measured phase considering the varying and the temporal change of dN/dH. Evolving dN/dH causes systematic refractivity biases, as it affects the beam trajectory, the associated target range, and the refractivity field sampled between selected targets of different heights.