Experimental Investigation of X-band Polarimetric Algorithm for Drop Size Distribution Retrieval

The goal of this study is to try to understand the relative accuracy of X-band DSD retrieval compared to those on S-band radar observation. However, the measured X-band polarization observation are biased by absorption due to the intervening rain medium and atmospheric gauses. Hence, it is imperative that X-band observations require attenuation correction. This paper investigates attenuation correction for X-band dual-polarization radar (XPOL) reflectivity and differential reflectivity in precipitation based on algorithms that use propagation phase measurements. Using the joint observations of XPOL/S-POL measurements and attenuation-correction schemes are evaluated. The study further explores sensitivity of attenuation correction to the raindrop axis ratio, temperature of water drop, and changes in DSD. In addition, comparison between various techniques for estimating raindrop size distribution (DSD) model parameters from the attenuation corrected X-band polarization radar data is presented. The DSD model is assumed to be a three parameter “normalized” gamma distribution. Coincident X-band (XPOL) and S-band (S-POL) dual-polarization radar measurements that where collected during the International H₂O Experiment (IHOP), as well as the coincident XPOL measurements over a 2D-video disdrometer from the Ionian Surface Rainfall Experiment (ISREX) are used to assess the X-band based DSD retrieval.