Dual-Doppler and Polarimetric Radar Analysis of Hail Events in Germany

摘要

Understanding the life cycle of precipitating systems is important for better nowcasting of significant weather and for improving weather prediction models. Doppler and polarimetric weather radars have the ability to look simultaneously into the microphysics and dynamics of precipitation systems. In this work we make use of these powerful tools to perform a combined analysis of the dynamics and microphysics of precipitation systems, in order to better understand storm development. By using data from multiple Doppler radars, the 3D wind field may be retrieved. Simultaneously, the polarimetric capability of the radars allows the retrieval of hydrometeor types and microphysical processes. Therefore, we are able to identify the processes through which precipitation systems evolve by revealing the interdependence between storm dynamics and microphysics. Prominent examples of such interactions are the development of socalled Zdr columns, that are associated with storm updrafts, and consequent freezing and potential hail formation; or regions of riming that are difficult to spot from polarimetry alone, but which require an updraft for supply of supercooled water, which could be seen in the wind field retrievals; or the development of lightning through lifting of graupel in convective updrafts that cause vertical electric charge separation. In this work we apply the Dual-Doppler technique DDA to analyze two large hail events that occurred near the Bonn and Jülich radars: the 5^thJuly 2015 and 22 June 2017. The life cycle of these 2 systems will be examined to better understand the formation and growth of hail, from the perspective of dynamics and microphysics.