Simulation and Evaluation of Climate Model CAS-ESM-C for Flow Field Modes in the Tropical Pacific Ocean in January

In this study, complex Empirical Orthogonal Function (CEOF) and wavelet analyses are applied to the 84-year simulation flow fields in January of the climate model CAS-ESM-C from 1922. The simulation results were compared with the actual situation and theoretical analysis solution to examine the simulation ability of the model for the upper equatorial ocean flow field. The main conclusions are as follows: (1) The variance contributions of the first three modes of the CEOF decomposition are 53.5%, 12.9%, and 9.5%, respectively. The cumulative variance contribution was 75.9%, which is higher than the actual situation. (2) The first and second eigenvector patterns are similar to the actual situation. The equator captures the flow fields, and the flow fields in the capture region are dominated by the partial latitudinal flow. The difference is that the equatorial capture area in this study is larger than the actual situation, and the longitudinal flow component, as well as the cross-equatorial flow, are also more obvious than that of the actual situation. (3) There is no linear trend in the real-time coefficient sequence of the first and second modes in this study, but this trend exists in the actual situation. The inter-annual and inter-decadal variations of the CEOF modes are similar to the actual situation. The inter-annual variation of 3–7 years in the first and second modes reflects ENSO (El Niño–Southern Oscillation). The inter-decadal variation of 22–23 years in the first mode is influenced by the North Pacific main climate modal PDO (Pacific Decadal Oscillation). The inter-decadal variation of 13 years in the second mode is influenced by the North Pacific secondary climate modal NPGO (North Pacific Gyre Oscillation). Both modes have an inter-decadal variation of 16 years, which may be related to the cross-flow in Indonesia. (4) The results in this paper show that the flow field is captured by the equator and zonal in the theoretical analytical solution. However, the flow field is pure zonal due to the absence of wind stress in the analytical solution. (5) The first (second) mode has dynamic SSTA (sea surface temperature anomaly) in the eastern (central) equatorial Pacific Ocean, which can be called the eastern (central) ENSO mode. The climate model performs well in simulating the upper flow field of the tropical Pacific Ocean.