北大西洋地区气候准20年周期的观测和模拟分析

北大西洋地区除了存在约70 a周期的AMO（Atlantic Multidecadal Oscillation，北大西洋年代际振荡）之外，历史长期气候记录中英格兰温度（Central England Temperature，CET）与格陵兰冰芯净雪累计率还存在显著的20 a周期波动。本研究利用CCSM4（Community Climate System Model version 4）耦合模式工业革命前控制试验（piControl）结果中的海表面温度（Sea Surface Temperature，SST），通过10～50 a带通滤波与扩展经验正交函数（Extended Empirical Orthogonal Function，EEOF）分解，得到在北大西洋副极地海区存在准20 a振荡的逆时针旋转模态。此周期与其临近地区的CET、格陵兰冰芯净雪累计率的准20 a振荡周期相吻合，说明这种北大西洋副极地海区准20 a振荡的海洋模态与其临近地区的大气准20 a振荡之间可能存在相应的联系。进一步利用CAM4（the Community Atmosphere Model version4）大气模式，以北大西洋副极地海区准20 a振荡SST旋转模态为强迫场进行敏感性试验，进一步验证了这种联系。

Observation and simulation analysis on climatic variability with quasi-20-year period in subpolar North Atlantic

Besides the well-known AMO (Atlantic Multidecadal Oscillation) with a period of 70 years in North Atlantic, longterm climatic records such as Central England Temperature (CET) and net snow accumulation from Greenland ice core also show a distinctive 20-year oscillation. The counterclockwise rotational mode of SST dipole in subpolar North Atlantic is obtained based on extended empirical orthogonal function (EEOF) method with 10-50-year bandpassed SST from piControl simulation of Community Climate System Model version 4 (CCSM4). The rotational mode of SST dipole shows quasi-20-year period which is consistent with the period of the surface air temperature (SAT) over England and Greenland. It may be possible to infer that the rotational mode of SST dipole with 20-year period can affect the climatic variability in the vicinity. The realtionship is verified by the sensitive experiments with the community atmosphere model version 4 (CAM4) which is forced by the rotational mode of SST dipole with quasi-20-year period.