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Reexamination of the Relationship between Tropical Cyclone Size and Intensity over the Western North Pacific

Abstract

This study reexamines the correlation between the size and intensity of tropical cyclones (TCs) over the western North Pacific from the perspective of individual TCs, rather than the previous large-sample framework mixing up all TC records. Statistics show that the positive size-intensity correlation based on individual TCs is relatively high. However, this correlation is obscured by mixing large samples. The weakened correlation based on all TC records is primarily due to the diversity in the size change relative to the same intensity change among TCs, which can be quantitatively measured by the linear regression coefficient (RC) of size against intensity. To further explore the factors that cause the variability in RCs that weakens the size-intensity correlation when considering all TC records, the TCs from 2001 to 2020 are classified into two groups according to their RC magnitudes, within which the high-RC TCs have a larger size expansion than the low-RC TCs given the same intensity change. Two key mechanisms responsible for the RC differences are proposed. First, the high-RC TCs are generally located at higher latitudes than the low-RC TCs, resulting in higher planetary vorticity and thus higher planetary angular momentum import at low levels. Second, the high-RC TCs are susceptible to stronger environmental vertical wind shear, leading to more prolific outer convection than the low-RC TCs. The positive feedback between outer diabatic heating and boundary layer inflow favors the inward import of absolute angular momentum in the outer region, thereby contributing to a larger size expansion in the high-RC TCs.

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Acknowledgements

This study is supported by the National Natural Science Foundation of China (Grant Nos. 41975071, 42175073) and the open project of the Shanghai Typhoon Institute, China Meteorological Administration (TFJJ202003).

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Correspondence to Guanghua Chen.

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Article Highlights

• In most tropical cyclones, size and intensity correlate well, especially during the development stage.

• Changing size-intensity relationships from storm to storm impairs the overall size-intensity correlation based on a mixture of all TC records.

• Genesis latitude and environmental vertical wind shear are two major factors affecting the relationship between the size and intensity of a tropical cyclone.

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Chen, K., Chen, G. & Shi, D. Reexamination of the Relationship between Tropical Cyclone Size and Intensity over the Western North Pacific. Adv. Atmos. Sci. (2022). https://doi.org/10.1007/s00376-022-1450-6

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  • DOI: https://doi.org/10.1007/s00376-022-1450-6

Key words

  • tropical cyclone
  • size and intensity
  • composite analysis
  • absolute angular momentum flux budget