A Dynamical Downscaling Framework for Tropical Cyclone Activity Over the Western North Pacific

Abstract

Due to the limited theoretical framework for tropical cyclone (TC) formation, the current downscaling strategies for TC activity face challenges in accurately capturing climate variations in TC genesis and the subsequent track and intensity in the western North Pacific (WNP). In this study, we introduce the recently developed dynamical genesis potential index (DGPI) into a new downscaling framework for TC activity in the WNP. Our findings indicate that the framework effectively reproduces the mean spatial distribution of TC genesis and track frequency, along with the frequency distribution of TC intensity. It also demonstrates strong skill in simulating variations in TC genesis, track, and intensity related to the El Niño-Southern Oscillation. Additionally, the temporal evolution of TC genesis frequency, track frequency, peak intensity, and power dissipation index in the WNP from 1979 to 2022 aligns closely with observations, showing significant correlation coefficients of 0.67, 0.75, 0.61, and 0.65, respectively. These results confirm the robustness of the downscaling framework in capturing both the mean and temporal features of TC activity in the WNP. Furthermore, an initial application to historical CMIP6 simulations suggests that climate change has contributed significantly to the poleward shift in TC activity from 1900 to 2014, driven by an El Niño-like sea surface temperature warming pattern. Given that this downscaling system relies solely on large-scale conditions and operates independently of historical observations, it offers a promising approach for investigating TC behavior in eras lacking reliable observations and in future warming scenarios.