The Dvorak technique has been widely used by operational warning centres around the world as a major analysis tool to determine the intensity of a tropical cyclone(TC).However,there exist noticeable differences in the...The Dvorak technique has been widely used by operational warning centres around the world as a major analysis tool to determine the intensity of a tropical cyclone(TC).However,there exist noticeable differences in the application of the technique among different warning centres.In particular,the weakening rules in the technique that governs the determination of TC intensity during the TC weakening stage constitute one such difference and are the subject of review in this paper.Three options to modify the weakening rules are introduced and evaluated based on verification against the best-track datasets from various centres.展开更多
Typhoon Morakot hit Taiwan in August 2009 and brought torrential rain and high death toll to the region. The registered maximum cumulative rainfall depth approached the world record of the greatest point rainfall. In ...Typhoon Morakot hit Taiwan in August 2009 and brought torrential rain and high death toll to the region. The registered maximum cumulative rainfall depth approached the world record of the greatest point rainfall. In this paper, the risk of experiencing rain episodes of similar severity in Hong Kong was assessed using the Advanced Research WRF(Weather Research and Forecast) model to simulate a direct hit of Typhoon Morakot to the city. A number of numerical experiments were conducted by transplanting the vortex of Morakot and the associated environmental conditions to the South China Sea to study the amount of rainfall that could fall in Hong Kong. The results revealed that the difference in the topography between Taiwan and Hong Kong alone accounted for more than 60% of the total rainfall registered in Taiwan. The enormous land mass of China to the north of Hong Kong would also weaken Morakot rapidly upon its landfall over the south China coast, causing a shift in its track and redistribution of rainfall, and a further reduction of the rainfall amount that Hong Kong would receive. Despite that, some experiments suggested that Hong Kong could receive nearly 800 mm of rainfall in 24 hours, a figure that would break the historical record of 697.1 mm set in 1889 in Hong Kong.展开更多
文摘The Dvorak technique has been widely used by operational warning centres around the world as a major analysis tool to determine the intensity of a tropical cyclone(TC).However,there exist noticeable differences in the application of the technique among different warning centres.In particular,the weakening rules in the technique that governs the determination of TC intensity during the TC weakening stage constitute one such difference and are the subject of review in this paper.Three options to modify the weakening rules are introduced and evaluated based on verification against the best-track datasets from various centres.
文摘Typhoon Morakot hit Taiwan in August 2009 and brought torrential rain and high death toll to the region. The registered maximum cumulative rainfall depth approached the world record of the greatest point rainfall. In this paper, the risk of experiencing rain episodes of similar severity in Hong Kong was assessed using the Advanced Research WRF(Weather Research and Forecast) model to simulate a direct hit of Typhoon Morakot to the city. A number of numerical experiments were conducted by transplanting the vortex of Morakot and the associated environmental conditions to the South China Sea to study the amount of rainfall that could fall in Hong Kong. The results revealed that the difference in the topography between Taiwan and Hong Kong alone accounted for more than 60% of the total rainfall registered in Taiwan. The enormous land mass of China to the north of Hong Kong would also weaken Morakot rapidly upon its landfall over the south China coast, causing a shift in its track and redistribution of rainfall, and a further reduction of the rainfall amount that Hong Kong would receive. Despite that, some experiments suggested that Hong Kong could receive nearly 800 mm of rainfall in 24 hours, a figure that would break the historical record of 697.1 mm set in 1889 in Hong Kong.
