Impact Of Coupled Model Horizontal Resolution On ENSO Simulation And Its Climate Effects Based On HighResMIP-PRIMAVERA Projec

ENSO(El Ni(?)o/Southern Oscillation)is the strongest signal of interannual variability in the Earth’s climate system,and its main features and teleconnections have been widely studied by numerous scholars.In order to investigate the impact of model horizontal resolution on the simulation of ENSO and its climate effects,this study uses six sets of model data provided by the High Res MIP-PRIMAVERA project,which only change the horizontal resolution,as well as commonly used observation and reanalysis data,to discuss the impact of model horizontal resolution on ENSO’s main features(such as its period,phase locking,and sea surface temperature anomalies)and climate effects(such as western North Pacific tropical cyclones,winter temperature and precipitation in eastern China).The main conclusions are as follows:(1)Increasing the horizontal resolution of coupled models helps improve the simulation of the 2-7 year main period and phase locking of ENSO.The improvement in phase locking simulation is mainly due to the high-resolution(HR)model’s simulation of SST anomaly amplitude during the developing and mature phases of ENSO being closer to observations.(2)During the El Ni(?)o developing phase,the HR models exhibit more significant and eastward-shifted SST anomalies compared to the low-resolution(LR)models,leading to a cooler western and warmer central Pacific along the equator and showing a dipole SST anomaly difference(opposite in La Ni(?)a years).This difference in SST anomalies between HR and LR models is due to the smaller cold tongue bias in the HR models.As a result,the convective anomalies associated with El Ni(?)o are more eastward-shifted,and further coupled with the ocean-atmosphere feedback process,ultimately leading to spatial distribution differences in dipole SST anomalies between HR and LR models.The spatial distribution differences of this dipole SST anomaly,as well as the differences in convective and diabatic heating anomalies,can trigger dipole large-scale circulation anomalies in the east-west direction in the convective and low-level of the western North Pacific.This leads to dipole differences in the density of western North Pacific tropical cyclone(WNP TC)genesis,making the HR model more consistent with observations in reproducing the impact of ENSO on WNP TC.(3)The impact of model resolution on SST anomalies during the mature phase of ENSO is similar to that during the developing phase.Compared to the LR models,the HR models exhibits more eastward-shifted SST anomalies and larger SST anomaly amplitudes,resulting in a dipole SST anomaly difference in the western and central-eastern equatorial Pacific.The smoother thermocline slope and warmer climatological SST in the equatorial central-eastern Pacific in the HR models are the reasons for the stronger ENSO amplitude and the westwardshifted center.(4)Both HR and LR models can reproduce the observed increase in winter temperatures and precipitation in the eastern coastal China to some extent and the increase in precipitation in the southeastern China caused by ENSO during its mature phase.However,the HR models show stronger and wider temperature and precipitation anomalies caused by ENSO.This is mainly due to the stronger cold sea temperature anomalies in the western equatorial Pacific in the HR models,leading to a stronger anticyclonic circulation anomaly in the convective and lower layers of the western North Pacific.This causes stronger southward flows on the west side of the anticyclone to transport more warm and humid air to the eastern China,resulting in stronger and wider temperature and precipitation anomalies.