By Institute of Atmospheric Physics, Chinese Academy of Sciences
November 25, 2022
Landfalling North Atlantic tropical cyclones (TCs) cause considerable financial damage to human civilization. TC intensity is the kinetic energy of a TC, which essentially comes from the energy in ocean heat content due to the fact that energy is conserved. Amongst all TCs, the peak strengths of strong TCs are the most related to the ocean heat content, especially that of the extratropical North Atlantic.
Understood also as typhoons or tropical cyclones, tropical cyclones are amongst the most harmful weather condition phenomena..
Where does that energy originated from?
Landfalling North Atlantic tropical cyclones (TCs) cause considerable financial damage to human civilization. Between 1900 and 2017, 197 North Atlantic TCs triggered 206 landfalls in the continental United States, leading to about US$ 2 trillion in damages. As natural weather catastrophes, TCs have substantial damaging power proportional to their strength.
Why do TCs have such effective harmful energy? Kerry Emanuels earlier research study on TC intensity recommended the “heat engine” concept, which discussed the strength of a TC from the viewpoint of the energy cycle and highlighted the reality that the energy stems from the warm ocean.
Schematic illustration of the oceanic thermal forcing of North Atlantic cyclones. Credit: Zhenxi Zhang.
Following this concept, Professor Zhenxi Zhang of Chinas Inner Mongolia University of Technology and Professor Wen Zhou of Chinas Fudan University investigated the spatial characteristics of the energy-driving North Atlantic TCs. Their findings were recently published in the journal Atmospheric and Oceanic Science Letters.
TC intensity is the kinetic energy of a TC, which basically comes from the energy in ocean heat content since energy is saved. Amongst all TCs, the peak intensities of strong TCs are the most associated to the ocean heat content, especially that of the extratropical North Atlantic. For that reason, the ocean heat material in this ocean region is the limiting element of strong TC peak intensity.
Coastal upwelling off northwest Africa and southern Europe can impact subsurface ocean temperature levels in the extratropical North Atlantic. “Therefore, the peak strength of strong TCs is likewise directly correlated with the water temperature level in these 2 upwelling regions on an interdecadal timescale”, concludes Professor Zhou.
Reference: “Oceanic thermal forcing of North Atlantic tropical cyclones” by Zhenxi Zhang and Wen Zhou, 8 September 2022, Atmospheric and Oceanic Science Letters.DOI: 10.1016/ j.aosl.2022.100286.
