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Disasters on the radar

Kobe University Professor Satoru Oishi stays minutes ahead of the next natural disaster, whatever it may be

Satoru Oishi knows disasters. A professor and certified weather forecaster at Kobe University’s Research Center for Urban Safety and Security, Oishi has studied everything from flash floods to volcanoes, mudslides, avalanches and lightning strikes. And with every new project, he makes it just a little bit safer to navigate the planet.

“Ultimately, I would like to help reduce the damage associated with disasters by using my knowledge of civil engineering and meteorology,” says Oishi, who has developed the world’s smallest and lightest weather forecasting device and a method for timing rescue efforts on active volcanos. Most recently, Oishi’s team has developed the fundamental mechanism of a lightning predictor, which they plan to present at the 2016 spring meeting of the Meteorological Society of Japan.

Right as rain

Central to Oishi’s work is radar, a technology used to determine the location and speed of nearby objects by scanning an area with radio waves and measuring the reflected waves. The use of radar is so ubiquitous in meteorology that most television weather reports display radar maps in the background. Continual improvements to radar technology by researchers such as Oishi are vital for the timely prediction of severe storms and other climate phenomena.

Oishi had been presenting his work on weather radar applications at a faculty showcase meeting in September 2010 when he was approached by Yoshiaki Takechi, an engineer with the marine electronics company Furuno Electric. Takechi and his team were developing maritime navigation systems, and were confronted by the major problem of ‘noisy’ signal arising from rain.

Oishi’s team worked with Furuno to build the world’s smallest and lightest rainfall monitoring system. The weather radar filled a space of just one cubic meter and weighed only 130 kilograms, with an observation range of 50 kilometers. Ice particles in the atmosphere above 4,000 meters act as the ‘seeds’ for rain. Using their radar device, the team could estimate the number of ice particles in the atmosphere to predict rainfall 10 to 20 minutes in advance — crucial information for disaster management, where some preparedness for flash floods or unexpected mudslides can mean the difference between life and death.

Volcanic eruptions

In October 2010, while researching floods in Indonesia, Oishi escaped a violent volcanic eruption of Mount Merapi. More than 300 people died in the initial and subsequent explosions, and many more would have been killed if not for search and rescue efforts. Three years later, Oishi was approached by Masato Iguchi, a professor of volcanology at Kyoto University, to collaborate on developing applications for radar technology — a proposition Oishi readily accepted.

A volcano’s eruption is accompanied by the release of plumes of ash and fragments of rock collectively called tephra. This tephra settles on the hillsides of volcanoes as unstable sediment. Severe rainfall can turn tephra into dangerous mudflows, landslides or even avalanches. Oishi and Iguchi wanted to develop a quick and reliable system for detecting unstable tephra to help authorities assess whether a disaster site is sufficiently safe to send rescue teams.

A volcano is said to be ‘inflated’ before an eruption, and to ‘shrink’ soon after. Oishi and Iguchi used a newly developed radar with a smaller detection range but higher temporal resolution to measure the amount of tephra discharged from a mountain by calculating its volume before and after an eruption (1). Oishi is still able to see the beauty in these calculations: “It makes me realize that the Earth is alive.”

The importance of this research was reinforced a bit closer to home in 2014, when Mount On-take, the second largest volcano in Japan, erupted suddenly one Sunday afternoon, resulting in 57 deaths. Recently, more volcanoes along the Pacific Ring of Fire have become active, with eruptions last year from four separate mountains.

Large plumes of ash and rock account for the ‘shrinking’ of volcanoes after an eruption, as seen in the 2013 release of Mount Sakurajima in Japan’s southern island of Kyushu.
Credit: © Richard Roscoe/Stocktrek Images/Getty Images


Professor OISHI Satoru (Research Center for Urban Safety and Security)

1.Oishi, S., Iida, M., Muranishi, M., Ogawa, M., Hapsari, R. I. & Iguchi, M. Mechanism of Volcanic Tephra Falling Detected by X-Band Multi-Parameter Radar. Journal of Disaster Research 11, 43–52 (2016).