Study reveals the mechanisms causing an equatorward shift in the lifetime maximum intensity locations of North Atlantic tropical cyclones

The lifetime maximum intensity (LMI) location of a tropical cyclone (TC) is the location where the cyclone reaches its strongest intensity. In a new study, scientists investigate the mechanisms by which the Atlantic Multidecadal Oscillation, a decades-long temperature variation in the Atlantic Ocean, is causing shifts in the LMI locations of North Atlantic cyclones. Their findings can help foresee future changes in the locations and patterns of TCs.

Title: Latitudinal Shift in Lifetime Maximum Intensity Location of North Atlantic Cyclones

Caption: A new study shows that the Atlantic Multidecadal Oscillation, along with changes in the track-related patterns of tropical cyclones, can cause a shift in the locations where the cyclones attain maximum intensity.

Credit: Korea Maritime & Ocean University

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Tropical cyclones (TCs) are extremely destructive weather events imperiling coastal communities. Long-term climatological changes can significantly alter the intensity and course of TCs, possibly making them more dangerous. A key factor for studying the activity of TCs and their societal impact is its lifetime maximum intensity (LMI) location, which is where a TC attains the strongest intensity of its lifetime.

The LMI locations of TCs over most oceans have migrated poleward in the past three decades. However, the LMI locations of North Atlantic TCs have shifted toward the Equator. A major influence in this shift is the Atlantic Multidecadal Oscillation (AMO)―a natural variability in sea surface temperatures (SST) in the North Atlantic Ocean spanning several decades. It is characterized by two phases: cold and warm. But there is limited research on how the AMO affects LMI location migration in the North Atlantic.

To further this understanding, a multi-university research team led by the Korea Maritime and Ocean University (KMOU), explored the shift in LMI latitude (Φ_LMI) in North Atlantic during peak hurricane season (August-October) between 1948 to 2018. Their research was made available online on 21 February 2022 and was published in Volume 49, Issue 5 of Geophysical Research Letters on 16 March 2022. “We designed a metric to evaluate how AMO-related variations in dominant track patterns (track Φ_LMI) and pure changes in the same track pattern (pure Φ_LMI) influence the total Φ_LMI migration. Based on this, we analyzed the annual mean variation in the LMI location,” explains Prof. Hyeong-Seog Kim of KMOU, who is the lead author of this study.

The team found that the total Φ_LMI shift is significantly affected by AMO, track Φ_LMI, and pure Φ_LMI. Changes in the AMO phase and related parameters, such as SST, potential intensity of TCs, and vertical wind shear, play a key role in causing track Φ_LMI and pure Φ_LMI variations. This, in turn, affects the location of origin and frequency of North Atlantic TCs, ultimately causing a shift in total Φ_LMI.

Consequently, during the warm phase of AMO, there is an increase in the frequency of TCs originating in the tropics and a decrease in cyclones originating in the subtropics. This results in a marked shift in the total Φ_LMI towards the equator. Conversely, during the cold phase, there is a poleward shift in the total Φ_LMI.

Expanding on these findings, Prof. Kim says, “Under the current warm AMO phase, the LMI locations of TCs have shifted equatorward in recent decades. Given the land-sea distribution in the Atlantic, this implies that TCs reach their LMI away from the land―potentially less destructive near the coasts. However, a poleward shift during the cold phase, likely to occur in the near future, combined with the effects of global warming, could mean that TCs last longer and cause far more damage on land.”

An improved understanding about the behavior of TCs is crucial, both from a scientific and socioeconomic perspective. This research provides insight into the shifting trends in North Atlantic TCs, which allows more foresight into the activity of future cyclones to enable better adaptation planning for coastal communities.

Reference

*Corresponding author’s email: dsrpark@knu.ac.kr 

About National Korea Maritime & Ocean University 

South Korea’s most prestigious university for maritime studies, transportation science and engineering, the National Korea Maritime & Ocean University is located on an island in Busan. The university was established in 1945 and since then has merged with other universities to currently being the only post-secondary institution that specializes in maritime sciences and engineering. It has four colleges that offer both undergraduate and graduate courses.  

Website: http://www.kmou.ac.kr/english/main.do

About the author

Prof. Hyeong-Seog Kim is an Associate Professor at the Ocean Science and Technology School, Korea Maritime and Ocean University. He has a PhD in Earth and Environmental Sciences from Seoul National University. Since the time of his PhD, he has been interested in the changes in tropical cyclone activity related to climate change and continues to study this relationship. He developed the objective clustering techniques applicable to tropical cyclone tracks. This technique has been applied in various ways to analyze and predict tropical cyclone activity. Previously, Prof. Kim completed his postdoctoral training at the Hurricane Research Group in Princeton University and the NOAA/Geophysical Fluid Dynamics Laboratory.