Drop Shape and Dsd Retrieval with an X-band Dual Polarization Radar

There is a renewed interest in the use of X-band weather radars, due to specific advantages such as applications to rainfall estimation in light rain, monitoring of sensitive areas that are inadequately covered by operational radar networks as well as the radar network concept introduced by the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) (Chandrasekar et al. 2004). The use of X-band measurements has been made easier by the advances in attenuation correction techniques based on polarimetric measurements. The initial set of attenuation correction algorithms was built from differential propagation phase (Φdp) (Bringi et al. 1991). Among the new algorithms that have been proposed, one of the most popular is that of Testud et al. (2000), that adopts a final value constraint as used in space borne radar. One of the advantages of polarimetric radar measurements is the internal self-consistency (Scarchilli et al. 1996), that expresses the synergy of the radar measurements of reflectivity factor (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp). Recently, it has been employed in a technique for attenuation and differential attenuation correction (Gorgucci et al. 2006a; Gorgucci and Baldini 2007). The technique, enforcing self-consistency between Kdp, and corrected Zh and Zdr measurements, improves the estimate provided by the methods that use Φdp as a constraint. Many studies on dual polarization radars have shown that observations at S-band can be used to derive raindrop size distribution parameters (Gorgucci et al. 2002; Bringi et al. 2003; Brandes et al. 2003) and mean raindrop shape (Gorgucci et al. 2000; Moisseev et al. 2006; Gorgucci et al. 2006b). This paper takes the next steps, namely the retrieval of drop shape and drop size distribution parameters using attenuation corrected polarimetric radar measurements at X-band.