TOKYO -- New technology utilizing broadcasting airwaves to quickly and precisely predict torrential rain and tornadoes is being tested in the Tokyo metropolitan area, providing hope for earlier warnings of such weather.

Industry, government and academic bodies including the National Institute of Information and Communications Technology (NICT) based in the Tokyo suburban city of Koganei led the development of the technology. It combines a new type of weather radar and terrestrial digital radio waves to estimate the amount of water vapor in the air that can become rain. Developers aim to put it into practical use before 2020 Tokyo Olympics and Paralympics, hoping it will contribute to the smooth operation of the games.

With conventional radars, heavy rainfall could not be predicted until the last minute. Localized downpours, dubbed "guerrilla rainstorms," occur when water vapor rises 4 to 6 kilometers from the ground to the upper atmosphere with the ascending air current. When cooled, these vapors condense into bigger droplets and descend to the lower atmosphere, often falling to the ground as rain in about 10 minutes. However, existing radars could only scan the lower atmosphere and it also took 5 to 10 minutes to analyze the collected data.

Developers say the new "multi parameter phased array weather radar" (MP-PAWR) being tested can predict torrential downpours and tornadoes 20 to 30 minutes before they occur. This is because it has a flat antenna that emits radio waves over a wider range than the rotating bowl-shaped antennas used in traditional radars. It is a combination of an MP radar that enables observation of the size of raindrops, and a phased array radar that provides 3-D scans of the structure of clouds in about 30 seconds.

Together with this radar, terrestrial radio waves are used to estimate the amount of water vapor to further enhance the accuracy of predictions. NICT officials noticed such waves traveled seventeen-trillionths of a second slower when the amount of water vapor in the air increased by 1 percent. Officials say a closer estimate of the timing of heavy rain can be obtained by incorporating the shift in the amount of water vapor in the air in weather forecasts.

The first experiments started last year. "We hope to put the technology, directly linked to the lives of people, into practical use as soon as possible," one NICT official commented. The official also cited a day-to-day benefit of the technology: People could "bring the laundry inside before it rains."

(Japanese original by Kazuki Mogami, City News Department)