A Japanese research team has succeeded in producing artificial rain for two consecutive years, proving the effectiveness of spraying liquid carbonic acid onto the bottoms of clouds.
The researchers from Kyushu University and Fukuoka University will report on their experiments with inducing artificial rainfall in February 2012 and March 2013 around the Izu Islands at a meeting of the Meteorological Society of Japan in Tokyo on May 15.
“Artificial rain cannot be created after drought comes following sunny days. More-than-usual rain can be produced during the rainy season and stored in dams if scarce rainfall is forecast for summertime,” said Taichi Maki, an emeritus professor at Kyushu University.
In the experiment March 14, planes were used to spray carbonic acid onto the bottoms of clouds about 1,400 meters thick situated north of Miyake Island and northeast of Mikura Island, about 180 km south of Tokyo. The clouds were sprayed for 10 minutes each.
As a result, the clouds along the 50-km-long, 2-km-wide flight path disappeared and caused rain. According to radar and meteorological satellite observations, the experiment directly caused an estimated 120,000 tons of precipitation.
Two hours later, the clouds vanished in a wider area about 50 km in diameter. An estimated 2 million tons of rain fell during the period, based on an assumption that 1 mm fell per hour.
About 5 grams per second of liquid carbonic acid at a temperature of 90 degrees below zero was sprayed. One gram is believed to have created some 10 trillion ice crystals, which grew into the snow particles that caused the rain.
The method of using liquid carbonic acid was invented by Norihiko Fukuda, an emeritus professor at the University of Utah who died in 2010. He conducted his first successful experiment near the island of Ikinoshima in Nagasaki Prefecture, in 1999.
Researchers have been accumulating data ever since. For practical application, permission needs to be obtained from the family of Fukuda and the University of Utah, which own the patents for the method.