2018 Volume 74 Issue 1 Pages 45-53
The purposes of this research were to increase artificial rainfall and evaluate the area affected by artificial rainfall. The experiment involved the seeding of liquid carbon dioxide at a height of 2500 m with a seeding rate of 11.1 g/s for 6 min around Karatsu, Saga, Japan on Dec. 26, 2013. The height of the cloud increased significantly, and a virga was observed under the cloud bottom at 2100 m at 30 min after the seeding. The cloud top of the previous seeding cloud was at 3350 m, the cloud bottom was at 2100 m, and the cloud depth was 1250 m. The cloud top after 30 min was at 3500 m, the cloud bottom was at 2100 m, the cloud depth was 1400 m, and the depth had increased by 150 m. The wind direction and speed around the seeding time at 3050 m were WSW and 13.9 m/s, respectively. At 1 h after the seeding, artificial clouds around Fukutsu and Munakata were clearly recognized, and after 1 h 30 min the clouds were around Kitakyushu. The final distance affected by artificial clouds was over 100 km after 2 h. The artificial rainfall (precipitation) amounts at Munakata, Yahata, and Shimonoseki were estimated to be 1.0, 1.0, and 0.5 mm, respectively. The amounts of artificial and natural rainfall or water resources were both estimated to be 0.15 million tons each after 2 h. The estimation of artificial rainfall by radar echo and the surface rainfall agreed well with each other. The artificial rainfall was observed at a target region and the amount of rainfall ultimately increased.