| The El Ni(?)o-Southern Oscillation(ENSO)and the Indian Ocean Dipole(IOD)are two major climatic patterns in the tropical Pacific Ocean and Indian Ocean,respectively.The simulations for these two patterns are one of the key issues of climate model devel-opment.In particular,how much of the improvement of physical modules and the in-crease of resolution can improve the simulation results of ENSO and IOD will be im-portant scientific guidance for climate model development.This thesis use the current mainstream climate model CESM(Community Earth System Model,version 1.2.0),combined with the observations and reanalysis data,and systematically study the simula-tion of ENSO and IOD with different atmospheric modules and horizontal resolutions.In addition,the reasons for the differences between the models from the dynamic point of view are also be discussed.The results show that the atmospheric module and horizontal resolution have signif-icant influence on the simulation of ENSO.CAM5 makes the period of two types of El Ni(?)o events longer,and increase the magnitude of the change of the thermocline depth anomaly in the eastern Pacific El Ni(?)o(EP El Ni(?)o)events.All the coupled experiments can accurately simulate the phase locking of the central Pacific El Ni(?)o(CP El Ni(?)o)events,but the experiments with CAM4 atmospheric module(CPL4)cannot realistically simulate the phase locking of the EP El Ni(?)o events.The CAM5 and low resolution make the El Ni(?)o stronger.The coupled experiments can accurately simulate the development of SSTA in the EP El Ni(?)o events,but is not good in the CP El Ni(?)o events.The simula-tion result of the zonal advection term is bad,especially the zonal temperature gradient by the mean current has a direct impact on the simulation results of the CP El Ni(?)o events.The negative abnormal intensity of precipitation in the CPL4 experiments are larger than that of CPL5 when simulating the La Nina events.The high resolution is ben-eficial to the simulation for the change of thermocline depth in the La Nina events.High resolution makes the period shorter,and the period of CPL5(1°)is closest to the observa-tion.Low resolution and CAM5 atmospheric module can increase the intensity of the La Nina events.The remainder of the equation plays an important role in the development of SSTA for the CPL5 experiments.The ocean model(POP2)could effectively simulate various features of the IOD.The coupled experiments run at the higher resolution yielded more realistic IOD period and intensity than their counterparts at the low resolution.The coupled experiments using CAM5 generally showed a better simulation skill in the tropical Indian SST climatology and phase-locking than those using CAM4,but the wind anomalies were stronger and the IOD period were longer in the former experiments than in the latter.In all coupled ex-periments,the IOD intensity was much stronger than the observed intensity,which is at-tributable to wind-thermocline depth feedback and thermocline depth-subsurface temper-ature feedback.The CAMS physics seems beneficial for the simulation of summer rain-fall over the eastern equatorial Indian Ocean and the CAM4 physics tends to produce less biases over the western equatorial Indian Ocean,whereas the higher resolution tends to generate unrealistically strong meridional winds.The IOD-ENSO relationship was cap-tured reasonably well in coupled experiments,with improvements in CAM5 relative to CAM4.However,the teleconnection of the IOD-Indian summer monsoon and ENSO-Indian summer monsoon was not realistically simulated in all experiments.Some similarities are found between the simulation of ENSO and IOD in four cou-pled experiments with different setting.The strength of ENSO and IOD in the coupled experiments are almost greater than that observed.Among the coupled experiments,the strength in the experiments with lower resolution are greater than in that with higher res-olution,and the strength in CPL5 is greater than that in CPL4. |
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