An approach to the hydrometeors classification for thunderclouds based on the X-band dual-polarization Doppler weather radar

In order to understand the main hydrometeor types affecting the electrification within a thunderstorm, a fuzzy logic algorithm for the classification of hydrometeor based on X-band dual-polarization Doppler weather radar measurements is described. Four radar parameters, namely, horizontal reflectivity (ZH), differential reflectivity (ZDR), specific differential phase (KDP) and correlation coefficient (ρHV), have been used in the algorithm. Hydrometeor is classified into 11 types which have closed relationships with the non-inductive electrification mechanism. The thresholds of polarizatic parameters for the 11 hydrometeor types are obtained by refering to the research results of the hydrometeor classification using S-, C- and X-band dual-polarization weather radars. In addition, environment temperature is added to restrict the altitude range of every hydrometeor type. The hydrometeors of the two convection processes taking place on 24 July 2007 in northwestern China are identified based on this algorithm. Furthermore, the characteristics of the radar parameters, ground electric field and flash frequency are analyzed preliminarily. Compared with the 3-D thunderstorm electrical model, the results show that the hydrometeor types could be identified effectively. It implies the fuzzy sets of polarimetric parameters and temperature ranges determined are basically valid. The charge regions could be inferred roughly based on the characteristics of KDP. All of these results are helpful for further understanding of the electrication mechanism within a thunderstorm.