Artificial rainfall experiment by seeding of liquid carbon dioxide above the Izu islands of Tokyo on December 15-16 in 2013

An artificial rainfall technique of liquid carbon dioxide (LCD) was used in experiments operated on Nii, Miyake and Mikura Islands in the Izu Islands of Tokyo in Japan on December 15-16, 2013. On Dec. 15, rain particles or graupel pellets struck the aircraft front window and virga or rain was observed under a cloud from the aircraft on the east leewardside of the seeded area under the condition of thin cloud of 760 m in depth until 30 minutes. On Dec. 16, rain or graupel struck the aircraft front window at 15 minutes after seeding and virga or rain under the cloud was observed at 37 minutes after the seeding under the condition of a thinner cloud of 610 m in depth. On Dec. 15, rain was recognized along the route of the seeding and a line-type trail of cloud disappeared was visibly recognized with an average width of 2 km. The development and disappearance of clouds were evaluated using satellite images near Mikura Island. On Dec. 16, a cloud developed immediately after the seeding and a line-type cloud running in the NNE-SSW direction was recognized on the satellite image. The cloud developed decreased in scale due to rain and the cloud disappeared was also recognized on a satellite image near Nii Island. On Dec. 15, an analysis showed the existence of following local effects of the seeding; the development of clouds at 700 hPa level higher than the seeding height, the appearance of rain at 850 hPa level around the seeding height, rainfall (virga) and a drastic increase in relative humidity at 925 hPa level lower than the seeding height, and finally the occurrence of artificial rains that were clarified by the upper weather maps based on meso scale model (MSM). The artificial rainfall experiments were succeeded.