A Three-Dimensional Simulation of the 10th August 2008 Storm Occurred Over Greece: AgI Seeding of Cell Merger by Using a Cloud Resolving Model

Abstract

A three-dimensional cloud resolving model is used to study the 10th of August intensive storm. This convective case occurred over north-central Greece and resembled similar characteristics of a cell merger, causing heavy rainfall, hailfall and high-frequency lightning. Three distinct numerical experiments have been performed. In the unseeded case, the structural and evolutionary properties of the reflectivity are analyzed, horizontally and vertically, in different simulation times. The 3-d numerical simulations suggest that the merger process occurred from two or three isolated single-cells, formed during their SW-NE motion. The merging process apparently alters the dynamical and microphysical properties through low and middle level forcing, increasing cloud diameters and cloud depths, enhancing convection, producing more graupel and ice particles and increasing radar reflectivity values. The resolved TITAN radar imageries depict a similar view of the storm structure, evolution and interactions of such merging processes. The model calculated maximum radar reflectivity values coincide with the recorded ones. For these specific cell mergers, two distinct seeding experiments were conducted, to find out the optimal seeding parameters, related to seeding criteria. Specific storm characteristics are demonstrated for the stages: before and after seeding, and before and after merging.