Effects of Equatorial Ocean Current Bias on Simulated El Nino Pattern in CMIP6 Models

This study utilized the Coupled Model Intercomparison Project Phase 6 (CMIP6) models to examine the simulations of equatorial ocean currents and explore their substantial influences on the systematic bias of westward-extended sea surface temperature anomalies (SSTA) pattern during El Nino. The results show that models simulate an excessive westward ocean current field over the equatorial central Pacific in the mean state. It tends to suppress the equatorial eastward ocean current anomalies with their maximum centering over the equatorial western Pacific in the El Nino developing phase. As a consequence, an overestimated zonal advective feedback toward the maritime continent exists, subsequently inducing the biased westward extension of SSTA pattern. Our results show that the mean-state performance of equatorial ocean currents plays a key role on simulations of El Nino evolution in CMIP6 models.

Automated summary

This study used CMIP6 models to investigate equatorial ocean currents and their influence on the biased westward extension of sea surface temperature anomalies (SSTA) during El Nino. The results show that the models simulate excessive westward ocean currents in the central equatorial Pacific, which suppresses the equatorial eastward ocean current anomalies in the El Nino developing phase. This leads to an overestimated zonal advective feedback and biases the westward extension of SSTA pattern.