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

Abstract

This study aims to assess the connections between El Niño–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 Niño (La Niña) 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 for GuamTC 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.