Impact of Anthropogenic Warming on Tropical Cyclone Translation speed and Intensity over East Asia

Abstract

Tropical cyclones (TCs) that move slowly over East Asia can produce devastating and prolonged impacts, yet the dominance of anthropogenic warming in modulating TC translation speed (TCTS) remain unclear. This study investigates the causes of the recent slowdown of autumn TCs over East Asia and assesses how future warming will alter TC motion and intensity by combining observational analyses with targeted numerical experiments. Using JTWC best-track data, we first examine seasonal TCTS and steering flow (STR) over the western North Pacific and East Asia, focusing on the 25–35°N band where many landfalling TCs affect East China, the Korean Peninsula, and Japan. After the late- 1990s shift to a predominantly negative phase of the Pacific Decadal Oscillation (PDO), the autumn mean flow over East Asia weakened, particularly in its zonal component, and the zonal components of both TCTS and STR exhibited significant decreasing trends and slower motion in 25–35°N. Linear regression analysis shows that removing the influence of PDO and other climate modes markedly reduces these trends, leaving no statistically significant residual signal attributable to anthropogenic warming. To corroborate this result, we perform Pseudo Natural Cooling (PNC) experiments with the WRF model for 21 TCs that move northward into East Asia, using CMIP6 historical and DAMIP hist- nat simulations to remove anthropogenic warming from the present climate. Differences in intensity and TCTS between the PNC and control experiments remain below ~2% and tracks are nearly identical, supporting the conclusion that current anthropogenic warming does not yet exert a dominant influence on East Asian TCTS. Future changes are investigated with pseudo-global-warming (PGW) experiments, in which thermodynamic forcings derived from 23 CMIP6 models under multiple SSP scenarios are imposed on the same 21 TC cases. In warmer climates, TCs become substantially stronger and wetter owing to enhanced surface latent heat flux, increased inner-core latent heating, and a deeper warm core, while the meridional temperature gradient and mid-latitude westerlies to the north of the storm weaken. As a result, the STR and TCTS both decrease, with the slowdown dominated by a reduction in the zonal (westerly) components in the mid-latitudes. Additional resolution-sensitivity experiments (9–3 km moving nest versus 9 km single domain) show that stronger TCs with higher inertial stability exhibit a additional slowdown consistent with an enhanced beta effect, but this contribution is secondary to the deceleration of the large-scale environmental flow. Overall, the recent observed slowdown of autumn TCs over East Asia is primarily linked to PDO-driven circulation changes, however, the anthropogenic warming is not yet dominant to control the TCTS over East Asia. The future anthropogenic warming is projected to produce more intense, wetter, and more slowly moving TCs in the mid-latitudes, amplifying the risk of prolonged TC hazards over East Asia.