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Torrential rains in July nearly quadruple over 45 years

Yomiuri Shimbun file photo
Heavy damage from the flooding of the Kuma River is seen in Hitoyoshi, Kumamoto Prefecture, on July 4, 2020.

The frequency of torrential downpours in July increased 3.8 fold over the 45-year period up to 2020, the Meteorological Research Institute (MRI) has announced.

The MRI believes that global warming and other factors have caused elongated bands of precipitation, which bring heavy rain, to occur more often.

The institute examined cases involving rainfall of 130 millimeters or more within three hours — situations in which an elongated precipitation band is likely to have occurred — analyzing them as concentrated downpours.

It looked at data collected nationwide by the Automated Meteorological Data Acquisition System from 1976 to 2020, and found that the frequency of concentrated downpours increased 120% for one-year periods and 280% for the end of the rainy season in July.

A series of disasters caused by torrential downpours have occurred in July in recent years. Elongated bands of precipitation were observed in connection with heavy rains in western Japan in 2018, and with the heavy rain in the Kyushu region in 2020.

“The risk of heavy rain has increased even in areas where torrential rains did not occur in the past. We urge people to be aware of the danger,” said Teruyuki Kato, director of the MRI’s Typhoon and Severe Weather Research department.