Why are more and more strong typhoons coming earlier?

A strong typhoon is a tropical cyclone with great destructive power. The maximum wind force near the center of a strong typhoon reaches 14 to 15, and the maximum wind speed exceeds 110 knots (203.7 kilometers per hour). It is an extreme weather phenomenon that often causes extreme disasters such as strong winds, heavy rains, floods and storm surges, causing significant casualties, economic losses and social impacts.

The active season for strong typhoons is from June to November in the northern hemisphere and from December to April of the following year in the southern hemisphere. Taking my country as an example, strong typhoons occur most frequently in autumn in my country, but in recent years, more and more strong typhoons have occurred in midsummer, such as "Dusurui" on July 23, 2023, "Fireworks" on July 21, 2021, and "Haigebi" on August 3, 2020, which caused huge economic losses to Wenzhou, Zhejiang.

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Why have more and more strong typhoons occurred earlier in recent years? Have the seasonal characteristics of strong typhoons changed? What causes this phenomenon? Are the causes of this change related to human activities? These are all questions that scientists are concerned about. Although there have been a lot of studies on the changes in the seasonal characteristics of strong typhoons (including the number, intensity and life history of cyclones), their seasonal cycle changes are still poorly understood. Understanding these issues is of great significance for human society to strengthen its understanding of extreme weather, improve its prediction and forecasting capabilities, and take timely response measures.

Recently, a scientific research team composed of researchers from Tsinghua University, University of Hawaii, Southern University of Science and Technology and Ocean University of China has made new progress in the research field of seasonal cyclical changes of strong typhoons.

They analyzed satellite data from 1981 to 2017 and found that from 1980 to the present, the strong typhoon season around the world has occurred 3 days earlier every decade, with the early rates of strong typhoon seasons in the Northern Hemisphere and Southern Hemisphere being 3.7 days and 3.2 days earlier every decade, respectively. This seasonal shift may be related to ocean warming, which is mainly caused by greenhouse gas emissions.

The internationally renowned academic journal Nature reported the above research results online under the title "Seasonal Advance of Intense Tropical Cyclones in a Warming Climate".

In order to find out the reasons for the early occurrence of the strong typhoon season, the research team deeply explored the seasonal changes of atmospheric and oceanic factors that cause the rapid intensification of strong typhoons. The results showed that the early occurrence of the strong typhoon season is related to the early rise in sea surface temperature and ocean heat content, which is mainly caused by the increase in greenhouse gas emissions caused by human activities.

Understanding the changing trends of the strong typhoon season is very important for social management, disaster prevention and emergency preparedness. The early arrival of the strong typhoon season will bring unexpected challenges to human production and life. It will overlap with other weather phenomena that originally occurred frequently during this period (such as extreme rainfall weather), resulting in more complex extreme weather events.

In the future, we need to pay close attention to the impact of the early strong typhoon season on human production and life, and conduct further research to develop better protection strategies for people and regions that are more affected by the early strong typhoon season.

References

[1]https://www.nature.com/articles/s41586-023-06544-0?utm_medium=organic_social&utm_source=zhihu&utm_campaign=CONR_PF020_ENGM_AP_CNCM_002EA_weeklyS

This article is a work of Science Popularization China-Starry Sky Project

Produced by: Science Popularization Department of China Association for Science and Technology

Producer｜China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

Author: Zeng Xinyue, popular science creator

Review | Huangfu Jingliang Associate Researcher, Institute of Atmospheric Physics, Chinese Academy of Sciences