Variations in Rainfall Structure of Western North Pacific Landfalling Tropical Cyclones in the Warming Climates

Observations and climate projections suggest a larger increase in tropical cyclone (TC)-induced rainfall than that can be explained by the Clausius-Clapeyron relationship of 7% increase in vapor content for each 1 degrees C degree rise in temperature. However, these studies using diverse data sources and methods over various periods show inconsistencies regarding the location of this increase - whether in the TC inner core or outer regions - and offer differing explanations for the reported trends. This study uses the Pseudo-global warming methodology on simulations of 117 western North Pacific TCs making landfall in Southeast Asia to investigate changes in TC rainfall structure by the end of the century under the SSP2-4.5 and SSP3-7.0 scenarios. Specifically, it tests the sensitivity of changing trends to various analysis methods used in previous studies and identifies the underlying physical mechanisms driving these changes. The findings indicate an amplified increase in rainfall in the TC inner core across all future scenarios, along with potentially decreased rainfall in the outer region under certain future climate conditions. Among TC categories, Supertyphoons exhibit the most significant increased rainfall across future states. Changes in TC primary and secondary circulations, TC structure, and the convergence of heat and moisture are the main factors shaping future rainfall patterns, outweighing the effects of changes in atmospheric and convective stability. Tropical cyclone (TC)-related rainfall is increasing with global warming. Typically, a 1 degrees C increase in temperature leads to about a 7% increase in the atmosphere's water vapor holding capacity. However, the rise in TC rainfall outpaces this rate. Observations indicate this enhanced increase occurs in the TC outer region due to greater environmental moisture. Contrarily, modeling future projections suggest this concentrates in the inner core due to intensified TCs. This study analyzes a large data set of 819 simulations from 117 TCs making landfall in Southeast Asia to capture changes in future rainfall patterns under two contemporary climate change scenarios. Our findings reveal that the enhanced increase occurs in the TC inner core in all future states, while rainfall in the outer region decreases under specific climate conditions. Supertyphoons generate the heaviest rainfall, with minimal variations observed across climate scenarios. Variations of all dynamic and thermodynamic factors closely tied to TC rainfall are investigated to provide a comprehensive picture of the physics behind the changes. The interplay between TC dynamics (e.g., primary and secondary circulations), TC structure, and thermodynamic conditions (e.g., convergence of moisture, and temperatures), plays a critical role in the changing behaviors of TC rainfall. Rainfall increases in the cyclone's inner core across all future states but decreases in the outer region under specific states Variations in cyclone circulations, structure, convergence of moisture and heat in future climates drive rainfall changing patterns Supertyphoons cause the heaviest rainfall compared to other categories, with slight variations noted across climate conditions