Impacts of Model Resolution on Responses of Western North Pacific Tropical Cyclones to ENSO in the HighResMIP-PRIMAVERA Ensemble

Abstract

The El Niño/Southern Oscillation (ENSO) is the major driver of interannual variations in the western North Pacific (WNP) tropical cyclones (TCs). Realistic reproduction of ENSO-WNPTC teleconnection in coupled models (CGCMs) is thus crucial for improved seasonal-to-interannual prediction of WNPTC activity. Here, basing on the outputs of six pairs of high-resolution (HR) and low-resolution (LR) CGCMs participating the HighResMIP-PRIMAVERA project, we showed that both HR and LR models can reproduce well the increased/decreased TC genesis and track in the southeastern WNP but the decreased/increased in the northwestern WNP in the developing years of El Niño/La Niña, but the HR models outperform the LR by simulating higher anomalous amplitudes closer to the observed. The better performance of HR than LR models is on one hand due to the generally increased frequency and variability of TCs in the HR models. On the other hand, the teleconnection of El Niño/La Niña to the WNP shows a dipole circulation difference between the HR and LR models with an anomalous cyclone/anticyclone in the southeastern WNP and anticyclone/cyclone in the northwestern WNP, which enhances the dipole TC genesis and track anomalies in the HR compared to the LR models. The teleconnection difference stems from the location differences in the ENSO-related SST and convection anomalies in the tropical Pacific, which may be ultimately linked to the reduced cold tongue biases in the HR compared to the LR models.