Artificial Cloud Seeding Using Liquid Carbon Dioxide: Comparisons of Experimental Data and Numerical Analyses

Abstract

n artificial seeding experiment was carried out over the Genkai Sea, Japan, using liquid carbon dioxide. The seeded cloud was followed by an aircraft and radar at Kyushu University. A radar-echo intensity of 19 dBZ was formed in the seeded cloud where no radar echo was observed previously. The results of the experiment are analyzed using a numerical model [Weather Research and Forecasting Model (WRF), version 3.1] to evaluate the effects of the artificial seeding. The numerically simulated radar echo has a slightly stronger intensity and wider area than that observed. The results of the experiments were similar to those produced by the numerical model, however. Evaporation of cloud liquid water; growth of snow particles that is due to deposition, autoconversion, aggregation, and collection; and convection caused by released latent heat are shown in the numerical results as effects of the seeding experiment. The falling snow particles cause downward flow, which is compensated for by upward flow that causes the formation of new cloud liquid water as a secondary effect of seeding, although this secondary effect is confirmed only in the numerical results.