Abstract:Solar forcing has an important impact on the formation and evolution of the Earth's climate.Under the influence of quasi-11-year solar cycle,the global climate changes with heterogeneity.The details of the response of the tropical Pacific sea surface temperature (SST) to solar 11-year variability and how it amplifies this response are important matters of discussion.Sunspot numbers (SSN) are used to represent the intensity of solar forcing.When the SSN increases,then the solar forcing strengthens.Positive and negative Niño3 indices are used to characterize the El Niño-like and La Niña-like SSTs.Bootstrap methods are used to verify the statistical significance of each signal.Next,based on the historical experiment from 24 CMIP5 (Coupled Model Intercomparison Project Phase 5),this paper evaluates the ability of models to simulate the observed significant La Niña-like SST anomalies in the tropical Pacific,which is stimulated by quasi-11-year solar cycle.By analyzing the reanalysis data,the “bottom-up” mechanism explains that the significant La Niña-like SST anomalies in the eastern tropical Pacific are likelier to occur in years with high solar activity.The results illustrate that two fifths of the CMIP5 models can effectively demonstrate the negative SST anomalies in the tropical eastern Pacific during the high solar forcing,which are segmented into the La Niña-like group.Meanwhile,another three fifths of the models can even simulate the opposite signal,which are known as the El Niño-like group.In order to explore the different simulation capabilities of the CMIP5 models,this paper analyzes the “bottom-up” mechanism in the model.The “bottom-up” mechanism is divided into two processes:evaporation process and thermostat process.The results show that whether or not the models can simulate the La Niña-like SST response depends on the strength of the thermostat process,and the thermostat process in La Niña-like group is stronger.However,it is observed that the evaporation process is not a key factor.