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摘要
Long-term simulations from the Community Earth System Model with the Whole Atmosphere Community Climate Model (CESM-WACCM) as its atmospheric component are used to investigate the asymmetry and the nonlinearity of the influences of El Nino-Southern Oscillation (ENSO) on the northern winter stratosphere. As in Part 1 of this study, four different types of ENSO are considered. The composite CESM-WACCM results first confirm the conclusions drawn from the observations, that the stratospheric polar jet responses to moderate El Nino and strong La Nina are stronger than those to strong El Nino and moderate La Nina. In association with the ENSO sea surface temperature (SST) patterns that are reproduced well in the model, the tropical rainfall response centers exhibit an asymmetric east-west shift between El Nino and La Nina, which directly leads to the nonlinear and asymmetric Pacific-North America responses in the extratropics. Accordingly, the strengthening (weakening) planetary wave response in the stratosphere during warm (cold) ENSO also exhibits nonlinear and asymmetric features. When the ENSO SST forcing is prescribed to be linear and symmetric in WACCM, the nonlinearity and asymmetry of the stratospheric responses to moderate ENSO reveal the dominant role of the inherent properties of the atmosphere. However, the absence of asymmetry and nonlinearity in the stratospheric responses to strong ENSO in our sensitivity experiments indicates that the asymmetry in SST forcing between strong El Nino and La Nina still plays an important role in the asymmetric and nonlinear influences of ENSO on the extratropics.
- 出版日期2016-8-16
- 单位中国科学院大学; 南京信息工程大学; 中国科学院大气物理研究所
