Numerical Simulation of the Ground-based Cloud Seeding Experiments Using AgI Module

The Weather Research and Forecast model coupled with AgI (Silver Iodide) module was used to investigate the effect of the cloud seeding on enhancing the precipitation. AgI module was considered for estimating emission, advection, diffusion and ice nucleation processes which include the condensation freezing (CDF), contact freezing (CNF) and deposition (DEP) as a heterogeneous nucleation. Nucleation ability of AgI for the immersion freezing is weaker than the other processes so that this study ignored the immersion freezing. This model was performed for the ground-based cloud seeding experiment in mountainous area (Daegwallyeong site) in east side of South Korea. The input data and the boundary conditions of model were improved using KLAPS (Korea Local Analysis and Prediction System) reanalysis data which have 5 km resolution. Four cloud seeding experiments were simulated on January 4 (2 times), March 5 (1 time) and April 3 (1 time) in 2014 with 1 km resolution. The seeding material (AgI) was assigned into one grid points in mountainous area (Daegwallyeong) and diffused by wind in the simulations. The first ice nucleation processes occurred 40~50 minutes after seeding in all experiments. Generated sequence charts of nucleation processes for AgI follow as: January cases - DEP > CNF > CDF (1st and 2nd experiment, T < -3°C) March case - CNF > DEP > CDF (T < -3°C) April case - Not generated of ice nucleation processes for AgI due to high temperature (T > 0°C). The weather condition has influenced on the success of cloud seeding experiment. These simulation results illustrate the suitable weather conditions (Temperature, Cloud water amount, Wind, Updraft velocity etc.) and the seeding time for a successful snow (precipitation) enhancement at the target area.

Acknowledgement : This work was supported by the Advanced Research on Applied Meteorology of National Institute of Meteorological Research (NIMR) funded by the Korea Meteorological Administration (KMA).