Jump in Fuji sightings since ’60s points to cleaner, drier air: school survey


Mount Fuji has become far more visible from Tokyo than half a century ago, possibly because the air around the capital has become cleaner and drier, a long-term survey by schools in Tokyo says.

Using a fixed point in the city of Musashino, western Tokyo, the observatory staff at Seikei junior high and high schools were able to see the 3,776-meter volcano on 126 days last year, or nearly six times more than in 1965, when it was viewable for 22 days, said Atsushi Miyashita, a teacher who joined the climate observation staff in 1990.

Since 1963, Seikei’s staff have been checking whether Mount Fuji is visible with the naked eye at 9 a.m. each day from the roof of a 25-meter school building some 80 km northeast of the iconic volcano. About 50 teachers and assistants have been involved in the project to date.

“I’ve never imagined that such a drastic change (in visibility) would occur,” Miyashita, 53, said.

Tokyo generated severe air pollution during the nation’s 20-year growth spurt that ended in the early 1970s, but that has been reduced markedly thanks to tightened emission controls.

The substantial improvement in visibility can also be attributed to drier air caused by the “heat island” effect. According to the Meteorological Agency, the humidity in central Tokyo has fallen to about 60 percent compared with 70 percent around 1960.

Miyashita, together with assistant teacher Saiki Mishima, 28, will present the outcome of the half-century survey at a meeting of the Meteorological Society of Japan to be held in Tokyo starting May 15.

Besides Mount Fuji, Seikei’s climate staff were able to see Mount Tsukuba in Ibaraki Prefecture on 100 days last year, although the mountain, about 70 km from the observatory, had been nearly unviewable till the early ’90s.