Investigation of Tropical Cyclone Landfall Frequency over East Asia in Present Climate and Future Projection by HiRAMs and HighResMIP GCMs

The atmospheric general circulation models (AGCMs) and coupled general circulation models (CGCMs) from High Resolution Model Intercomparison Project (HighResMIP) are adopted to investigate the ability of models to simulate the tropical cyclone (TC) landfall frequency over East Asia (including the South China Sea [SCS], Taiwan and coastal areas of East China [TWCN] and Japan [JP]) in the present period (1979-2008) and future projection (2021-2050) under the Shared Socioeconomic Pathways 5–8.5 (SSP5-8.5) scenarios. The results revealed that the AGCMs and CGCMs realistically captured TC genesis counts, track frequency, and tracks associated with TCs striking the JP. However, fewer TCs were steered toward the TWCN and SCS in both simulations because of the low-level cyclonic circulation anomaly induced by the overestimation of monsoon trough, which substantially modified steering flow. This overestimation primarily resulted from different factors in individual runs, including the overestimation of sea surface temperature (SST)-precipitation relationship in the Atmospheric Model Intercomparison Project (AMIP) type simulation in AGCMs, and the El Nino-like SST anomaly in CGCMs.

The total TC landfall numbers over East Asia are projected to decrease by 5.7% (4.2%) in AGCMs (CGCMs) during the period 2021-2050. Among the regions, the reduction in TC landfall frequency is relatively consistent and significant only in the SCS, with a 10.1% decrease in AGCMs and an 8.7% decrease in CGCMs, respectively. The landfall change over East Asia is insignificant because the TC genesis frequency and steering flows remain almost unchanged from the present period to the near future.