An improved hydrometeor identification method for X-band dual-polarization radar and its application for one summer Hailstorm over Northern China.

Currently, high-resolution severe storm observations obtained by vehicle-mounted mobile X-band dual-polarization radar (X-pol) are widely used in severe storm structure and dynamics studies; however, the identification of hailstones based on X-pol is still rare, leading to the limited application of X-pol in identifying hydrometeors in the microphysical processes of severe storms. Based on previous works, this study constructs an improved X-pol hydrometeor identification (HID) method for hailstorms; the hydrometeor categories include a rain-hail mixtures (RH) category indicating hailstones are melting or experiencing wet growth, and the correlation coefficient between horizontally and vertically polarized echoes (ρ HV) is used to locate the local mixed phase region in storms to avoid misclassifications of hydrometeors resulted by environmental temperature in this local mixed phase region. The improved HID method can see liquid water information above the melting layer; it provides a possibility to observe the microphysical process of hailstones wet growth above the melting layer. Furthermore, this improved HID method was utilized to study the high spatiotemporal resolution data collected by the Institute of Atmospheric Physics of Chinese Academy of Sciences (IAP) X-pol for one summer hailstorm over northern China. The results indicate that the identified RH is consistent with the surface hail record of National weather observatory of China Meteorological Administration (CMA), the specific differential phase (K DP) column is more sensitive than the differential reflectivity (Z DR) column for indicating the updraft zone movement, and we considered that the relative position between the key area of hail (KAH, where above the Z DR column, Z DR ~ −2 to 0 dB, Z H ~ ≥ 50 dB Z) and the updraft zone (indicated by the Z DR , K DP column) will determine the evolution of hail. Furthermore, high-density graupels (HDGs) in the upper layer of the KAH may be the source of RH embryos, and these HDGs collect liquid droplets from the liquid water-rich (LWR) area located behind the KAH to form a large number of RH in the lower layer of the KAH. These characteristics are important for hailstone forecasting and warnings. • Constructing an improved X-band dual-polarization radar (X-pol) hydrometeor identification (HID) method for hailstorms. • This improved method showed its superiority in observing liquid water information above the melting layer within storms. • The results reveal how the polarization parameters of X-pol indicate the generation and extinction of hail. [ABSTRACT FROM AUTHOR]