Effects of cloud seeding on precipitation and seasonal case analyses based on long-term numerical simulations

This study quantitatively analyzes the effects of cloud seeding on precipitation and seasonal variations over the Boryeong Dam region, which has the lowest dam storage in South Korea, based on a 1-year numerical simulation for 2021. The Morrison microphysics scheme in the Weather Research and Forecasting (WRF) model was modified to estimate differences in precipitation between simulations with seeding materials (AgI and CaCl2; SEED) and without them (UNSD). The effect of cloud seeding on increasing precipitation or artificial rainfall (AR) between the two simulations was highest in August (average 0.21 mm; 31% of the SEED-simulated monthly mean) and lowest in January (average 0.003 mm; 30%). This large AR may be attributed to a combination of abundant moisture from the summer monsoon climate and enhanced cloud droplet growth resulting from cloud seeding. In the analysis of seasonal representative cases, cloud seeding demonstrated more pronounced effects in spring and summer, with mean 180-min accumulated AR values of 0.46 and 0.43 mm, respectively, within the study area. In the spring, where an actual flight experiment was conducted, the simulated mean 180-min accumulated AR (1.41 mm) in the flight experiment area was close to the observed value (1.61 mm) for the same area. Additionally, cloud seeding promoted the hygroscopic growth of water vapor, thereby reducing the cloud water mixing ratio and increasing the rain water mixing ratio. Seasonal cross-sectional analysis further highlighted the impact of cloud seeding on changes in these two mixing ratios, with the most pronounced effects observed in spring and summer.