The Tropical Pacific Interannual Variability Simulated with LASG/IAP Climate System Model FGOALS_gl

The authors evaluate the performance of the fast coupled version of LASG/IAP climate system model FGOALS_gl on simulating the interannual variability in the tropical Pacific. Compared with the observations, the main characteristics of the interannual variability in the tropical Pacific Ocean is reasonably reproduced. Nonetheless, the coupled model also shows clear biases. The amplitude of El Niño－Southern Oscillation (ENSO) is overestimated. The model also fails in simulating the irregularity of ENSO cycle. The overestimation of ENSO amplitude is mainly caused by the weaker climate mean trade wind and the associated mean state bias of the ocean. The phase locking of ENSO appears in boreal spring and summer in the model, which is attributed to the bias of sea surface temperature (SST) annual cycle in the tropical Pacific Ocean. The observed eastward propagation of SST anomalies is not evident in the model, and this is related to the simulated single developing mode of ENSO (SST-mode). The negative feedback of ENSO is explained by the “Recharge－Discharge Oscillator” theory, in which the change of the equatorial Pacific Ocean heat content acts as an important transitioner for ENSO. The sea level pressure anomalies feature a Southern Oscillation (SO)－like pattern in boreal winter associated with El Niño events, and the corresponding geopotential height at 200 hPa exhibits a Pacific－North America (PNA) teleconnection pattern.