A C-band fully self-consistent methodology to correct attenuation and differential attenuation

Although is not a major error source at C-band, attenuation may degrade the radar measurement to a considerable degree in situations like a precipitation event in the radar shadow of a strong convective cell, or may affect precipitation accumulation estimates at distances far from the radar site. For C-band radars, attenuation can be corrected using different methods depending on the type of measurements involved. The early attenuation correction procedures were based on iterative approaches without bounds and were unstable (Aydin et al. 1989). Studying the relation between differential phase (Φdp) and cumulative attenuation as well as differential attenuation at S-, C-, and X-band frequencies, Bringi et al. (1990) explored a simple attenuation correction procedure based on linear relations between Φdp and cumulative path attenuation and differential attenuation. More recently, the cumulative attenuation estimate provided by cumulative differential phase was used as a constraint to obtain the profile of specific attenuation have been proposed (Testud et al., 2000). In the latter two techniques, a constant coefficient is used to convert Φdp to cumulative attenuation. Alternatives techniques, employing empirical adjustment to the conversion coefficient, were also suggested (Smyth and Illingworth 1999, Bringi et al. 2001). One of the advantages of polarimetric radar measurements in rain is their internal self-consistency. The self-consistency principle (Scarchilli et al. 1996) takes advantage of the synergy among the radar measurements, namely reflectivity factor (Zh), differential reflectivity (Zdr), and specific differential propagation phase (Kdp) and has been proven as a powerful tool in several applications. Gorgucci et al. (2006) applied it in a methododology for attenuation and differential attenuation correction at X-band. This paper presents an advance of this methodology and evaluates it both using C-band profiles generated from S-band radar measurements collected by the NCAR S-Pol radar and C-band radar data collected by the Polar 55C radar over the region of Rome region (Italy).