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2021.08.17

[SPORTS X] World First! Heavy Rainfall Becomes Detectable in People-Friendly Tokyo 2020 Innovation

Do you know it is said that instances of so-called “guerilla rain” have increased recently in Japan? As the name suggests, this is localized, heavy rain that falls unexpectedly, and it was previously difficult to predict accurately even in weather forecasts. However, with the hosting of the Tokyo 2020 Olympic and Paralympic Games as an impetus, the latest weather radar has been developed to make it possible to detect these downpours. What benefits does the Guerilla Rain and Tornado Advance Prediction Project, an innovation promoted by the Cabinet Office, have for us?

What are the first cross-ministerial initiatives in science, technology, and innovation for the 2020 Tokyo Olympics and Paralympics?




Tokyo was determined as the venue for the 2020 Olympic and Paralympic Games in 2013, but carrying out a large international event safely and smoothly in a metropolis with a population of over 14 million was not expected to be easy. The Cabinet Office therefore brought together experts in various fields and related institutions, such as in Tokyo, to hold a meeting of the Task Force on Science, Technology, and Innovation for the 2020 Tokyo Olympics and Paralympics in 2016. Nine projects were launched for the success of the Tokyo 2020 Olympic and Paralympic Games.

One among them was the Guerilla Rain and Tornado Advance Prediction Project described in this article. Because many athletes, staff, and spectators gather in the venues for the Olympic and Paralympic Games, the goal of the project was to make predictions with time to spare to guide visitors appropriately and ensure safety even in the event that a heavy downpour or a tornado occurred on the day of a match.

Grasping the structure of rain clouds in only 30 seconds guarantees time to take precautions and find shelter


From materials from the Task Force on Science, Technology, and Innovation for the 2020 Tokyo Olympics and Paralympics (third meeting)


The three-dimensional parabolic weather radar used in conventional weather observation measured rainfall distribution over an interval of several minutes by rotating mechanically. However, the cumulonimbus clouds that cause guerilla rain may develop in a short span of approximately 10 minutes, so it was not unusual for rain to have already started falling at the time the prediction was made.

In contrast, the multi-parameter phased array weather radar (MP-PAWR) developed in this project makes full use of functions such as simultaneous observation in more than 10 directions to grasp the structural arrangement of rain clouds in only 30 seconds. It is the world’s first working-model weather radar that makes it possible to detect rapidly developing cumulonimbus clouds. Thanks to this, previously impossible forecasting including detection of guerilla rain 20 minutes before it occurs and prediction of strong winds and lightning 30 minutes in advance have become possible, guaranteeing enough time to take precautions and find shelter.

This project was headed by the national Cross-Ministerial Strategic Innovation Promotion Program (SIP), for realizing innovation that surpasses the boundaries of government department categories and traditional fields. Until now, weather concerns were for the Japan Meteorological Agency, disaster preparedness concerns were for the Fire and Disaster Management Agency, and so on, with a fixed department for each specialization. This program was started to promote such cross-ministerial initiatives. The Guerilla Rain and Tornado Advance Prediction Project featured in this article has advanced world-first innovations through the cooperation of various organizations and companies including the Ministry of Land, Infrastructure, Transport and Tourism; the National Research Institute for Earth Science and Disaster Resilience; the National Institute of Information and Communications Technology; the Japan Weather Association; Osaka University; and Toshiba Corporation.

How does this apply to our lives? Quick predictions using an app




Unfortunately, most of the Tokyo 2020 Olympic and Paralympic Games events have barred spectators because of the COVID-19 pandemic. Opportunities to use this device at game venues may therefore be scarce. However, this innovation holds potential to be of great use in our lives in the future.

At present, the generally available smartphone application “tenki.jp Tokyo Weather Radar” is still limited to the scope of the Greater Tokyo Area, but it can predict guerilla rain sooner than other resources. If you know, for example, that there will be a sudden downpour in the vicinity of your transfer station on your return home, you can avoid getting rained on by changing your route or traveling at a different time.

In addition, event promoters will be able to obtain information about guerilla rain in advance to guide attendees safely. Wheelchair users, people who walk with a cane, and people pushing strollers who have difficulty using an umbrella can also reduce the risk of encountering unexpected heavy rain. Furthermore, if the application coordinates transit systems such as Metropolitan Expressway and subways to distribute information to local governments, it will also be able to avert accidents and disasters before they occur.

Significant innovation occurred in Japan and made our lives dramatically more convenient when the country hosted the Tokyo 1964 Olympic and Paralympic Games, too. For example, the shinkansen began service. Whereas travel between Tokyo and Osaka previously took six and a half hours, the opening of the shinkansen shortened it to four hours. Further progress of technological innovation has now cut that time to less than two and a half hours. Perhaps it can be said that, in addition to these innovations that make life convenient and comfortable, the 2020 Olympic and Paralympic Games are distinctive for their many people-friendly innovations. We are steadily approaching a society where everyone, including the elderly, those with small children in tow, and wheelchair users, can travel and live their lives with peace of mind.

text by Kaori Hamanaka(Parasapo Lab)
photo by Shutterstock

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