Future Tropical Cyclones in the Western North Pacific under Global Warming Trend: Track-Cluster Analysis

Abstract This study investigates how tropical cyclones (TCs) in the western North Pacific (WNP) respond to the global warming trend using TC-track clustering analysis and data from a modified High Resolution Atmospheric Model (HiRAM). The dataset includes four future projections driven by different CMIP5-based warming patterns of sea surface temperatures (SSTs), incorporating inter-annual SST variability aligned with the present-day simulation. Under the RCP8.5 scenario, WNP TCs are projected to undergo the following changes across all the six categorized clusters and four projections in the late 21 st century: fewer TCs, the distribution of TC lifetime maximum intensity (LMI) extending toward higher intensity, and enhanced mean intensification rates. Inter-cluster and inter-ensemble variations exist in projected changes of other TC parameters. For instance, two clusters demonstrate a substantial and statistically meaningful increase in the mean LMI, resulting from enhanced mean intensification rates and nearly-unchanged mean intensifying durations. One of these two clusters compromises stronger TCs affecting a wide range of coastal regions, with characteristics well replicated in the HiRAM present-day simulation. Our calculations of the seasonal-mean ventilation index suggest either less-supportive or mostly-unchanged environmental favorability for WNP TC development under the warming scenario. This contrasts with the projected enhancement of TC intensification rates across all clusters, and does not comprehensively explain the dramatic reduction of HiRAM TCs. The main text also delves into changes in the geographic distribution of TC occurrence, genesis and LMI, and the interplay between each TC parameter and environmental favorability for TC development under the imposed global warming trend.