【気候科学】全世界で熱帯低気圧の移動速度が低下している

The translation speed of tropical cyclones - the speed at which they move across the planet - has slowed by about 10% over the past 70 years, finds a paper in this week’s Nature. The paper also reports a significant slowdown of tropical cyclones over certain land areas, which consequently leads to an increased potential for storm-related devastation.

Global warming is projected to increase the severity of the strongest tropical cyclones, but warming may bring other, potentially even more serious, effects, such as the general weakening of summertime tropical atmospheric circulation. In addition to circulation changes, anthropogenic warming causes increases in atmospheric water-vapour capacity, which is expected to increase precipitation rates. Rain rates near the centres of tropical cyclones are also expected to increase along with increasing global temperatures.

James Kossin assesses the tropical cyclone record and shows that their translation speed has slowed by about 10% globally from 1949 to 2016, with more extreme slowdowns over some land areas. The author finds a significant slowdown of 30% and 20%, respectively, over land areas affected by western North Pacific and North Atlantic tropical cyclones, and a significant 19% slowdown is found over the Australian region. He concludes that even independent of changes in storm severity, tropical cyclones are staying over a given area for longer periods, with an increased potential for extreme rainfall and storm-induced damages.