The occurrence of seedable clouds in the warm season for mitigating water shortage problems

Water shortages have recently become a serious problem for many cities in Japan. Since 2006, Japanese Cloud-seeding Experiments for Precipitation Augmentation (JCSEPA) have been conducted in Japan for mitigating water shortages in summer. Initially, to determine the intensive observation area, we identified areas with frequent droughts where potential clouds for seeding appeared frequently from 1994 to 2008 using Geostationary Meteorological Satellite (GMS) and ground observation data. In this study, the water shortage period was defined as the period when water supplies were limited and a seedable cloud was defined as a cloud that did not bring heavy rainfall. The Sikoku area was identified as a candidate for observations. On comparing months with and without water shortages, the total rainfall was small in the water shortage months, while the occurrence of clouds did not differ. For convenience, the precipitation efficiency was defined as the ratio of the areal rainfall rate to the occurrence of clouds. The clouds in the months of water shortage had a low efficiency of precipitation. Nevertheless, potentially seedable clouds existed in the period of water shortage.