Simulated Connections between ENSO and Tropical Cyclones near Guam in a High-Resolution GFDL Coupled Climate Model: Implications for Seasonal Forecasting

This study aims to assess the connections between El Nino-Southern Oscillation (ENSO) and tropical cyclones near Guam (GuamTCs) using the state-of-the-art Geophysical Fluid Dynamics Laboratory (GFDL) Forecast-Oriented Low Ocean Resolution version of CM2.5 (FLOR). In observations, more (fewer) GuamTCs occur in El Nino (LaNina) years, and the ENSO-GuamTC connections arise from TC genesis locations in ENSO phases. The observed ENSO-GuamTC connections are realistically simulated in the two control experiments that use two versions of FLOR: the standard version and another with flux adjustments (FLOR-FA). The ENSO-GuamTC connections in FLOR-FA are closer to observations than those in FLOR because of a better representation of TC genesis during ENSO phases. The physical mechanisms underlying the observed ENSO-GuamTC connections are further supported in the long-term control experiments with FLOR and FLOR-FA. The ENSO-GuamTC connections in sea surface temperature (SST)-and sea surface salinity (SSS)-restoring experiments with FLOR 1990 strongly resemble the observations, suggesting the ENSO-GuamTC connections arise substantially from the forcing of SST. The prediction skill of FLOR-FA forGuamTC frequency is quite promising in terms of correlation and root-mean-square error and is higher than that of FLOR for the period 1980-2014. This study shows the capability of global climate models (FLOR and FLOR-FA) in simulating the linkage between ENSO and TC activity near a highly localized region (i.e., Guam) and in predicting the frequency of TCs at the subbasin scale.