Evaluation of Tropical Cyclone Simulations by the High-Resolution Climate System Model FGOALS-f3-H and the Role of Air–Sea Feedbacks in the Western North Pacific

This study evaluates the performance of a high-resolution climate model FGOALS-f3-H in simulating tropical cyclones (TCs) over the western North Pacific (WNP), with focus on comparing differences between coupled and atmosphere-only simulations. TC climatology, variability, and environmental factors are evaluated. The results show that (1) both simulations reproduce basic TC characteristics, though notable biases from model deficiencies and air–sea coupling remain. The coupled model shows an asymmetric response of surface heat fluxes (SHF) to TC-induced sea surface temperature (SST) cooling depending on TC intensity, which reduces (slightly increases) SHF for intense (weak) TCs. This results in less precipitation, more diffuse warm cores, and weaker winds for intense TCs, but more precipitation for weak TCs. The asymmetric response also makes more realistic TC intensity distributions and wind–pressure relations (WPR) in the coupled model, although both models overestimate total TC numbers and concentrate in producing medium-intensity TCs. (2) For TC frequency and genesis, both models show profound overestimation in the eastern WNP, and the coupled model has stronger overestimation, which can be explained by the impacts of warm climatological SST biases that enhance TC-favorable environmental factors related with eastward-shifted western Pacific tropical easterly jet (WPTEJ) and weakened subtropical high (WPSH), among which relative humidity and vertical wind shear dominate the genesis potential index (GPI) biases. (3) Both models cannot capture comparable correlations with El Niño–Southern Oscillation (ENSO), but the atmosphere-only model can capture the correlation with eastern Indian Ocean SST, showing better interannual variability. The coupled model can capture the interannual modulation of the upper-ocean heat content (OHC), although it simulates poorer interannual variations and unrealistic TC–ENSO response. These findings highlight that air–sea coupling corrects TC intensity-related biases, but worsens TC locations and variability due to common tropical biases in coupled models.