Stage-dependence of Tropical Cyclone Seeds and Their Future Change

Seminar by Dr. Jung-Eun Chu from City University of HongKong

22 May 2023
KST 10:30 – 11:30

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

Tropical cyclones (TCs), the generic name for typhoons, are among the most destructive natural hazards. It is important to understand how climate change affects TC frequency, to minimize human and economic losses. However, the origin of the TCs from the initial precursory vortex, called a TC seed, and their survival rate (i.e., the proportion that successfully develops into TCs) are not well understood. Key challenges are mainly due to a lack of consensus in TC seed definition and a lack of computing resources for TC modeling. This study aims to meet the above challenges, through the following tasks: (1) to identify the representation of TC seeds and survival rate based on three different stages: early-, intermediate- and mature-stage definitions; (2) to investigate the contribution of TC seeds and survival rate to future changes in TC genesis using a high-resolution fully-coupled Community Earth System Model (CESM) simulations. Experiments with fixed CO2 concentrations under present-day, doubling, and quadrupling conditions with an atmospheric resolution of 0.25° and an ocean resolution of 0.1° were used. Our results show that the spatial distributions of the TC seeds and survival rate are largely depends on the different stages of the seed definition. TC seeds defined by early-stage definition show more equatorward distribution with a strong connection to vertical velocity, while those defined by intermediate- and mature-stage are located 2-5° poleward. In response to greenhouse gas warming, TC seeds obtained by all three definitions exhibit a statistically significant reduction in the frequency of TC seeds while survival rate remains unchanged. This study is the first to examine the sensitivity of TC seeds and survival rate to various stages of the definition and their future change using the highest resolution fully coupled model global warming simulations.