Title: Finite-amplitude Rossby waves and summertime heavy rainfall events

[Abstract]
A potential-vorticity-based theory of finite-amplitude Rossby waves (Prof. Noboru Nakamura’s theory) is presented in comparison with traditional linear theory and other finite-amplitude theories. The PV-based finite-amplitude theory is applied to understand summertime long-lasting heavy rainfall events (HPEs) in South Korea. From 29-year (1996–2024) column water vapors and precipitation data, we found that quasi-stationary atmospheric rivers (QSARs) are associated with the long-lasting HPEs. The dynamical mechanisms of the HPEs related to QSARs are investigated using local PV based finite-amplitude wave activity (LWA) using the ERA-5 reanalysis data. Data analysis indicates that downstream amplification of the LWA occurred 1–2 weeks before summer long-duration HPEs over South Korea. These results suggest that the LWA offers the potential to be used in forecasting summertime long-lasting HPEs in South Korea. Further potential application of the LWA will be discussed.