A numerical study of winter orographic seeding experiments in Korea using the Weather Research and Forecasting model

Abstract

Ice nucleation processes by silver iodide were parameterized and implemented into the Weather Research and Forecasting model to perform winter orographic cloud seeding experiment in an eastern mountainous region of the Korean Peninsula. Cloud seeding at a mountain site resulted in production of ice crystals, mostly by deposition and condensation freezing nucleation of seeding material and depletion of water drops by ice crystals themselves and by snow and graupel particles grown from these ice crystals but importantly precipitation increased over the target area to the west of the seeding site. Sensitivity test showed that increasing the release rate of seeding material led to enhanced precipitation. Interestingly, dominant ice crystal nucleation mode was different for different aerosol concentrations: deposition and condensation freezing nucleation were dominantly responsible for ice crystal formation for maritime aerosol type (i.e., low concentration) while the dominant mode was contact freezing nucleation for continental aerosol type (i.e., high concentration). When seeding material was released at a low-altitude site (i.e., upslope of mountain), it was not successfully transported upward to the target area but instead dispersed along the direction of the mountain ridges by the barrier jets.