[Press Release] Wind patterns off the Philippines−Taiwan influence tropical cyclone formation

A group of researchers led by Dr. Yu-Lin Chang from the Application Laboratory of Japan Agency for Marine-Earth Science and Technology (JAMSTEC) analyzed a combination of observed and reanalyzed atmospheric and oceanic data, demonstrating that the distribution of tropical cyclone formation is influenced by the Philippines−Taiwan Oscillation (PTO). The PTO involves a north-south oscillation in wind patterns off the Philippines and Taiwan inter-annually, which happens to be the tropical cyclone formation region in the Western Pacific Ocean. The relation was found between the differences in horizontal wind vorticity (PTO index) and the occurrence of tropical cyclone formation in the same area between years 1979 and 2014. The results showed that when the PTO index is positive (i.e. when the trade wind weakens, the wind off the Philippines strengthens in an anticlockwise direction and the wind off Taiwan strengthens in a clockwise direction), tropical cyclones form more frequently south of 18°N. Conversely, when the PTO index is negative (i.e. when the anticlockwise wind off the Philippines and the clockwise wind off Taiwan both weaken), tropical cyclones form more frequently north of 18°N. Furthermore, when the PTO index is positive, the number of tropical cyclones that approach Japan increases.

The above results were published in Scientific Reports on November 29, 2018 (JST).

Title: Philippines−Taiwan Oscillations and its connection to tropical cyclone frequency in the western North Pacific Ocean
Authors: Yu-Lin K. Chang1, Yasumasa Miyazawa1, Tsubasa Kodaira2, Swadhin K. Behera1
Affiliations: 1. JAMSTEC 2. The University of Tokyo

Please read the following press release for more details.

Press Release (November 29, 2018): http://www.jamstec.go.jp/e/about/press_release/20181129/

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