Abstract
The current study conducted numerical experiments using nonhydrostatic mesoscale meteorological model to evaluate and verify the mitigating effect of weather modification by cloud seeding on torrential rains. Based on simulated two heavy rain events in the Kitakyushu and Tokai regions of Japan, sensitivity analysis was performed by manipulating some conditions of cloud seeding implementation, i.e., area, height, time, etc., in incremental steps. Some standpoints of evaluation were introduced in the analysis to clarify whether and how far cloud seeding have a significant influence on precipitation systems. Results show that rainfall area and hourly rainfall, as well as maximum areal rainfall, can be decreased by cloud seeding, depending on the condition of its implementation, and that the number of cases with rainfall mitigation tends to be greater than that with rainfall promotion. It was also clarified that rainfall mitigation by cloud seeding can be attributed to the leeward migration and/or diffusion of precipitation particles with excessive increase of ice crystals in upper layers of the atmosphere.
