运用中国160站月平均气温和NCEP/NCAR 再分析数据, 在结合近30年中国1月地面气温年际异常变化可能机理基础上, 分析了2008年1月气温异常变化的原因。结果表明: 2008年1月中国大范围气温异常偏低, 其异常变化与同期北大西洋西风急流及其相联系的北大西洋涛动遥相关环流异常有密切的关系。北大西洋急流加强东扩, 北大西洋涛动正异常, 从北大西洋经欧亚中高纬到中国北方出现波状环流异常, 贝加尔湖南侧气压偏高, 冷空气活动偏强, 是中国1月气温偏低的主要环流因子。进一步分析发现, 2008年1月中国低温还受到了平流层的影响。平流层环流异常开始于2007年9月, 对流层从2007年12月开始, 两者都在2008年1月达到最强。从平流层环流显著异常的波源区有异常的波作用量向西向下传播, 在北大西洋东部到西欧上空平流层和对流层的波向量耦合, 导致对流层该地区上空高压脊扰动加强, 扰动向北的经向热输送异常偏强, 锋区向北扩展, 相应急流异常偏北东扩; 通过波流相互作用, 扰动能量向下游频散, 引起相应遥相关环流异常, 导致2008年1月中国低温。
In terms of the monthly NCEP/NCAR data and the 160 site temperature data from the National Climate Center (NCC), the main causes of anomalously low surface air temperature in January 2008 over China are investigated on the basis of the possible mechanism of typical episodes occurring in recent 30 years. Results show that the January surface air temperature in 2008 is lower than normal in most part of China, which is linked closely to the teleconnection circulation anomaly associated with the North Atlantic Oscillation (NAO) and the jet stream over the North Atlantic. The main circulation causes for the lower temperature is that the jet stream becomes strong and expands to the East Atlantic with positive NAO as a wave train circulation anomaly pattern appearing from the North Atlantic to East Asian area, and higher pressure occurs to the south of Baikal, indicating that the cold air is stronger than normal. The circulation anomalies in the troposphere are influenced by those from the stratosphere. The circulation anomalies in the stratosphere occurred earlier in September 2007 than those in the troposphere appearing in December 2007. And both of them became strongest in January 2008. Anomalous wave fluxes propagate from the wave source in the stratosphere over East Asia downward and westward, and in the upper troposphere over the North Atlantic there is a remarkable convergence of wave fluxes, leading to enhancing of the ridge there with stronger northward heat transportation and the related front zone shifting, and the jet stream anomalously developing and easterly expanding. Thereby anomalous disturbance energy will disperse downwards by wave-flow interaction and induce teleconnection circulation anomalies, resulting in the lower temperature episode of 2008 in China.