New research has revealed that the observed average moving speed (or translation speed) of tropical cyclones making landfall over the coast of China dropped by 11% between 1961 and 2017. These slow-moving tropical cyclones brought about 20% more local total rainfall on average when compared with fast-moving ones, resulting in greater flood risks in the region.
The study also found that the occurrence of tropical cyclones with lower moving speeds and higher total rainfalls became more frequent after 1990 in the Pearl River Delta. The discovery offers invaluable insights that will enable the development of better flood management and adaptation strategies in the coastal region of China which is under threat due to tropical cyclones.
Over 400 tropical cyclones under study
The research team led by Dr Li Jianfeng, Assistant Professor of the Department of Geography at HKBU, studied 406 tropical cyclones which made landfall and lasted for more than two days over the coast of China, and specifically the Pearl River Delta where Hong Kong is located, between 1961 and 2017. The study, which started in 2018, aimed to investigate the trend of tropical cyclones’ moving speeds and its correlation with the volume of rainfall in the long run.
The research team analysed track data of the 406 tropical cyclones from the International Best Track Archive for Climate Stewardship (IBTrACS) and numerical simulations of eight Global Climate Models (GCMs) developed by meteorological and modelling centres around the world. IBTrACS is one of the most commonly used datasets for tropical cyclone studies, while GCMs are important tools for scientific communities to investigate and project climate behaviour.
Tropical cyclone’s moving speed correlates negatively with local rainfall volume
The team found that the observed moving speed of the tropical cyclones underwent a significant drop of 11%, decreasing from 21 km per hour in 1961 to 18.6 km per hour in 2017. The simulated moving speed also showed a drop of 10%, decreasing from 21.2 km per hour to 19.1 km per hour during the same period.
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Materials provided by Hong Kong Baptist University. Note: Content may be edited for style and length.