A government-sponsored scientific research project involved with dropsonde observations will significantly improve the accuracy of typhoon forecasts, further enhancing the effectiveness of disaster-prevention measures to be launched when typhoons strike Taiwan, according to the National Science Council.
The tragedy of losing lives and properties during typhoon seasons became more pronounced in the past few years, due to real-estate developments in densely populated areas.
Especially in September 2001, when Typhoon Nari swept the country, leaving the Taipei metropolitan area flooded for days, inaccurate weather forecasts were blamed by not only residents but also decisionmakers involved with taking emergency measures.
To improve the accuracy of typhoon forecasting, the council launched a three-year research project at a cost of NT$90 million last year August, focusing on "dropsonde observation" as the most important part of the typhoon-surveillance project.
"It's worthwhile, when compared with the huge financial losses caused by natural disasters triggered by typhoons," council Vice-Chairman Liao Chun-chen (廖俊臣) said at a press conference yesterday.
According to project coordinator Chun-Chieh Wu (吳俊傑), an atmospheric scientist at National Taiwan University, a G100 Astra SPX aircraft operated by Aerospace Industrial Development Corp (AIDC) has been equipped with the Airborne Vertical Atmosphere Profiling System, with which scientists can trace dropsondes thrown outside a typhoon at a height of 12,800m and measure the atmospheric state parameters during their descent.
By using Global Positioning System (GPS) receivers, specifications captured by dropsonde sensors, such as air pressure, temperature, humidity, wind speed and others, could be obtained immediately.
"The real-time data, which we scientists can use to picture the structure of a typhoon and predict its track, can be transferred to the Central Weather Bureau from the aircraft in seconds," Wu said.
Wu said the US' experience of flying synoptic surveillance missions around typhoons suggest that the observation produces a 10 to 30 percent reduction in track forecast errors involving hurricanes.
The project is co-hosted by Po-Hsiung Lin (林博雄), another National Taiwan University atmospheric scientist and Yeh Tien-chiang (葉天降), director of the bureau's Weather Forecast Center.
According to researchers, the best time to carry out the observation is 24 to 60 hours prior to the approach of a typhoon. The aircraft will spend five hours flying outside a typhoon to capture data by throwing 15 to 20 dropsondes.
The 450g disposable dropsondes, known as the RD93 GPS Dropsonde, is made by the Vaisala Group in Finland. Each one costs NT$3,000.
The project makes Taiwan only the second country in the world after the US working on typhoon surveillance involving dropsonde observations in this region of the northwest Pacific.
According to researchers, the US Navy, which terminated a similar observation project in 1987 in Guam, will resume observations this summer focusing on a more challenging task -- capturing data by flying into the eye of the typhoon.
Wu said that combining data from Taiwan and the US Navy would reveal the real face of a typhoon, a fascinating complex fluid mechanism still puzzling scientists.
Wu said that the data from the project would be shared with nearby countries such as Japan and the Phillipines.