Projected Changes in Extratropical Cyclone Activity Under Climate Change Scenario in East Asia

Abstract

Understanding the projected changes in extratropical cyclone (ETC) activity under climate change scenarios is essential for anticipating regional climate impacts and developing effective adaptation strategies. This study investigated how the ETC activity over East Asia responds to future climate conditions by dynamically downscaling simulations from the UK Earth System Model (UKESM6), which is part of Coupled Model Intercomparison Project Phase 6 (CMIP6), using four regional climate models (RCMs): GRIMs, WRF, RegCM, and CCLM. To robustly assess the changes in ETC characteristics, both Eulerian bandpass filtering and Lagrangian cyclone tracking methods were employed under four Shared Socioeconomic Pathway scenarios: SSP1‐2.6, SSP2‐4.5, SSP3‐7.0, and SSP5‐8.5. The results highlight the added value of RCMs in significantly reducing the biases present in UKESM6 over complex terrain, primarily owing to the improved representation of high‐resolution topography and the associated dynamical processes. Distinct trends emerged between the land and ocean regions: ETC activity over land showed limited changes regardless of the emission scenario intensity, whereas oceanic ETC activity significantly declined under intensified warming scenarios (SSP3‐7.0 and SSP5‐8.5). Disentangling ETC‐related intensity changes from cyclone passage frequency also revealed that similar bulk ETC changes can arise from different combinations of these contributions depending on the scenario, highlighting the scenario‐dependent responses of oceanic and inland ETC activity. Overall, the results indicate that future ETC changes over East Asia are strongly scenario dependent, with relatively weak inland changes but a more robust weakening over the marine storm‐track region under stronger warming.