Origin of outer tropical cyclone rainbands

• Published in: Nature communications Vol. 14; no. 1; p. 7061
• Main Authors: Yu, Cheng-Ku, Lin, Che-Yu, Pun, Chi-Hang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03.11.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 704/106/35/823; 704/4111; Cyclones; Dominance; Humanities and Social Sciences; multidisciplinary; Precipitation; Science; Science (multidisciplinary); Tropical cyclones
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-42896-x

Outer tropical cyclone rainbands (TCRs) are a concentrated region of heavy precipitation and hazardous weather within tropical cyclones (TCs). Outer TCRs pose considerable risk to human societies, but their origin remains unresolved. Here, we identify a total of 1029 outer TCRs at their formative stage from 95 TCs and present a large collection of radar observations in order to establish a robust foundation of the natural diversity of rainband origin. The results show the dominance of outer origin for the observed outer TCRs, in distinct contrast to theoretical modeling works of outer TCRs, which propose inner-origin scenarios. Our analysis also suggests that squall-line dynamics are a common, but not the sole, mechanism responsible for outer TCR formation. The nature of preexisting outer precipitation is found to be an important factor to influence the squall-line and non-squall-line outer TCR initiation. Convectively active, hazardous rainbands within tropical cyclones are shown to originate primarily from outside the inner core of the cyclone. This outer-origin dominance is partly attributed to squall-line processes and deserves future attention.