The rainfall estimates RDP based on the specific differential phase shift KDP are unaffected by errors in radar calibration and attenuation along the path.
However, due to the signal fluctuations the estimates RDP can be very noisy at low and moderate rain rates. In order to improve the accuracy of the rainfall estimates KDP is to be estimated over a long path. In this way an error due to the reflectivity gradients, which could occur along a long path, can be introduced. In this paper we have analyzed two cases of reflectivity gradients along the path filled with rain; the first one, where the reflectivity varies linearly on dB scale that can be used to approximate regions with a steady increase or decrease of dBZ, and the other
corresponding to sharp reflectivity gradient within the measurement cell, where an intense rainshaft is located adjacent in range to weak-echo regions. In both cases the
error structure is discussed and the sensitivity of the normalized bias in KDP-based rainfall estimates is evaluated from a theoretical viewpoint and by simulation
