Weather forecasters use their personal judgment to tweak the results of computerized weather modeling and then draw weather maps by hand.
A notice on the wall of the Taipei Metro’s Ximen Station declares: “Flood Depth Record of Typhoon Nari, Sept. 17, 2001.” Below the notice is a line marked “540 cm.” This high-water mark reminds us of the destructive power of typhoons. Unfortunately, Taiwan is well acquainted with natural disasters. In 2009, Typhoon Morakot caused landslides that buried Kaohsiung’s Xiaolin Village, and killed a total of nearly 700 people across our island. In 1996, Typhoon Herb caused coastal flooding in Central and Southern Taiwan, washed out a portion of the Alishan Highway’s roadbed, and extinguished more than 50 lives. In 1999, the powerful Jiji Earthquake destroyed thousands of buildings and killed more than 2,400 people.
These were only the worst of the natural disasters to strike Taiwan in the last 30 years: we also contend with multiple less-severe typhoons and earthquakes every year. This “annual training” provides us with unusual insight into natural disasters and has taught us to coexist with them. As the saying goes, long illness makes the patient a good doctor. Taiwan’s frequent typhoons and earthquakes have honed our disaster response capabilities and provided us with valuable experience that we can share with other nations.
Located in the Northwest Pacific typhoon corridor and on the seismically active Ring of Fire, Taiwan is struck by many tropical cyclones and earthquakes. According to the Ministry of the Interior, typhoons have been Taiwan’s most frequently occurring natural disaster of the last 50 years, followed by flooding and earthquakes.
Figures from the Central Weather Bureau (CWB) show an average of three to five typhoons making landfall on Taiwan every year. We also experience roughly 100 earthquakes per day, and an average of 2.8 quakes of magnitude 6.0 or greater every year. These compound natural disasters have had a profound impact on Taiwanese society, and have spurred government, industry and academia to further their understanding of natural disasters in hopes of developing better methods for predicting and providing alerts about them.
The “wind chaser” project
Roughly two-thirds of Taiwan sits above 900 meters of elevation. We also have more than 250 mountains that rise above 3,000 meters. This is important because, as Professor Huang Jr-chuan of the National Taiwan University (NTU) Department of Geography explains, the complex ways typhoons interact with tall mountains complicate weather and typhoon forecasting.
Professor Wu Chun-chieh of NTU’s Department of Atmospheric Sciences has been conducting aerial observations since 2003, using GPS dropsondes to advance understanding of typhoon dynamics and improve the accuracy of typhoon track forecasting. His work has propelled Taiwan into a leading role in Northwest Pacific and East Asian typhoon research.
The CWB has improved its own observation techniques over the last decade, in part by installing regional rainfall radar systems in urban areas to gather highly accurate data on local low-altitude rainfall.
The CWB’s “octagon” contains all kinds of traditional and modern earthquake detection equipment.
Typhoon response
Huang Treng-shi, deputy director of the CWB’s Weather Forecast Center, says that Taiwan’s current advanced weather data integration system knits together data from satellites, radar, ground-based observations, and precipitation measurements.
The center initiates its typhoon warning procedures the day before a typhoon’s periphery reaches Taiwan’s coastal waters, which helps both the government and the public respond appropriately to the impending threat through measures such as positioning pumps in flood zones, evacuating residents from landslide-prone areas in the mountains, closing roads and urban floodgates, and, for members of the public, ensuring they have adequate food and water supplies, and securing items that might fall from buildings. One to two hours before landfall, the CWB uses the Public Warning System to send alerts to the mobile phones of citizens in the areas at the greatest risk of storm damage, urging them to take shelter.
While Japan, Korea, Taiwan and the Philippines are all prone to typhoon strikes, Taiwan is the only one among them to have an officially defined system of “typhoon holidays.” When a typhoon is forecast to bring average wind speeds of at least Force 7 on the Beaufort scale (50 km/h) or gusts of at least Force 10 (89 km/h) to a given area, the relevant city and county governments can declare a holiday from work and school. Encouraging the public to stay at home reduces the risk that people will come to harm in a storm.
Nowadays, the CWB is able to offer precise, highly localized weather forecasts, which helps avoid unnecessary declarations of typhoon holidays. Huang says that whereas the CWB used to provide weather forecasts focused on Taiwan’s 22 counties and municipalities, it now offers forecasts down to the scale of its 368 townships and municipal districts, and provides forecasts for some 1,000 locations. In fact, the bureau’s current technology can accurately predict the weather three to six hours ahead for areas as small as three kilometers across.
Taiwan’s weather forecasting challenge
Taiwan’s typhoon track forecasting is on par with that of technologically advanced nations such as Japan and the US. Huang explains that accurately predicting the intensity of wind and rain, the timing of their arrival, and the damage they will cause, are critical challenges.
Taiwan has become something of an international weather laboratory as a result of the number of typhoons we face every year and the comprehensiveness of our ground-based radar observation network and infrastructure. Last year, the CWB carried out a joint experiment on the measurement of violent rainfall with US and Japanese researchers. It has also long provided assistance to the Philippines in the areas of typhoon forecasting and radar and data-processing systems. More recently, the bureau has strengthened its cooperation with New Southbound Policy partner nations by sharing its experience in typhoon preparedness and response.
“Long illness makes a good doctor. We should be proud of Taiwan’s typhoon disaster management experience.” Huang says that the government does a good job disseminating typhoon information to the public, and that it has good typhoon response procedures in place. He feels that other nations could learn from them, citing the speed with which we typically reopen damaged roadways after a disaster, and how soon after Typhoon Nari we were able to restart the Metro system and raise the height of flood protection at its station entrances.
Chen Kuo-chang, director of the CWB’s Seismological Center, says that though we can issue alerts when earthquakes occur, the quakes themselves are difficult to predict. Nonetheless, the CWB’s cooperation with academia to find earthquake precursors represents a big step forward in quake prediction.
100 quakes a day
Earthquakes are another big worry for those of us who live in Taiwan.
Our island sits on the Pacific Ring of Fire, which is the planet’s most geologically active region and home to more than 85% of its earthquakes and volcanic activity. Chen Kuo-chang, director of the CWB’s Seismological Center, explains that Taiwan’s many earthquakes are caused by the convergence of the Eurasian Plate and the Philippine Sea Plate. “Taiwan is a world leader in earthquake frequency.”
According to the CWB, Taiwan averages 100 earthquakes per day, but the majority are small tremors that mostly go unfelt. An earthquake needs to have a magnitude of at least 3.5, and generally at least 4.5, to be felt by people near its epicenter. While Taiwan averages just 2.8 earthquakes of magnitude 6.0 or above per year, we saw a dozen of that size in 2022, the most in a year since 1999’s Jiji Earthquake.
National earthquake alerts
People worry a great deal about earthquakes. Is it possible to predict them? Chen says that while earthquake prediction technology is still a work in progress, we have already developed the means to provide alerts. By integrating monitoring instruments with other technology, upon detecting seismic waves the system is able to rapidly estimate the extent of the area that will be affected by the earthquake and the quake’s destructive power, and then issue an alert, giving people several seconds to take appropriate action before the shaking reaches them.
In 2016, a large earthquake centered in the Meinong District of Kaohsiung caused the collapse of a residential building in Tainan. The event prompted academia and the CWB to jointly develop an automated system for locating earthquakes that is capable of pinpointing a quake’s epicenter within a few seconds of its onset. The system then estimates the quake’s size and intensity across Taiwan, and passes this information to the earthquake rapid alert system for distribution. In the event of an earthquake of magnitude 5.0 or more, or a prediction that any locality will experience a seismic intensity of 4 or greater, the system is able to send out cellphone alerts to the public in the affected cities and counties within ten seconds. Chen says that with the automated location system already more than 60% accurate, the CWB hopes to reduce the notification time to seven seconds in 2023 and to five seconds in the future. “Meeting the five-second challenge would make our earthquake alerts the quickest in the world, faster even than in Japan.”
Last year, Professor Yen Horng-yuan and his team in the Earth Sciences Department at National Central University achieved a breakthrough in earthquake prediction by collating geoelectric, geomagnetic and ionospheric data on earthquakes of magnitude 6 or greater occurring between 2013 and 2018. Big-data analysis revealed corresponding anomalies that show promise as quake predictors. The CWB is planning a project for next year that will look further into the topic of detectable earthquake precursors.
More than 70% of Taiwan’s earthquakes occur off the coast of Yilan and Hualien. Chen explains that this area is a subduction zone at the edge of the Eurasian Plate, and is geologically complex, with a number of fracture zones. The Manila Trench, which runs from near Fangshan, Pingtung County, down to the Philippines, also has the potential to generate large earthquakes and tsunamis. Taiwan has therefore installed observation stations on the seafloor that are connected via submarine cables that run from Toucheng in Yilan to Fangshan, and southward from Fangshan along the eastern edge of the Manila Trench. This system has reduced the time it takes to calculate the parameters of an offshore earthquake from 35 seconds to just 20-some seconds and enabled the CWB to provide tsunami warnings. To date, only Taiwan, Japan and the US have established this kind of undersea monitoring network.
When a magnitude 7.8 earthquake on the Turkey–Syria border in February 2023 brought down tens of thousands of buildings and killed more than 50,000 people, the earthquake resistance of buildings became a hot topic once again.
Chang Wen-yen, dean of the National Dong Hwa University College of Environmental Studies and Oceanography and a research fellow with the Institute of Earth Sciences at Academia Sinica, says that the damage caused by earthquakes depends on the seismic resistance of old buildings. In addition to replacing such buildings or making them more earthquake-proof, we could further reduce earthquake harms by conducting non-destructive testing of the homes of disadvantaged residents, and perhaps providing them with grants to purchase or lease earthquake-resistant furniture.
“Can a butterfly flapping its wings in Brazil cause a tornado in Texas?” Dubbed the “butterfly effect” by American meteorologist Edward Norton Lorenz (it is an expression of “chaos theory”), the term highlights the idea that small events or phenomena can cause large, connected reactions to ripple through dynamic systems. The concept also helps remind us that the natural world is complex in ways that extend beyond the limits of scientific understanding. If we wish to thrive in spite of natural disasters, we can never cease our efforts to enhance community resilience.
For more pictures, please click 《Hard-Earned Knowledge: Taiwan’s Typhoon and Earthquake Response Experience》
