摘要:本文利用日本第二次全球大气再分析项目（JRA-55）提供的逐日积雪深度数据、欧洲中期天气预报中心（ECMWF）提供的全球再分析数据及Hadley海温数据分析了春季欧亚大陆积雪异常模态及其与北大西洋海温的遥相关关系，并通过模式模拟分析验证。结果表明：春季欧亚大陆雪深前两种模态差异显著，分别表现为东、西区域同向变化及反向变化两种非对称形态。其中，同期北大西洋“三极子型”海温模态与“马鞍型”海温模态分别与雪深第一、第二模态具有显著相关关系，这两种海温模态下对应的北半球中高纬波动作用通量分别呈丝绸之路（SRP）型和欧亚波列（EU）型两种传播特征，对中高纬西风气流的位置、强度产生了不同影响，进而对欧亚雪深分布产生遥相关作用。通过局地多尺度能量涡度分析法（Localized Multiscale Energy and Vorticity Analysis，简称MSE-VA）表明，北大西洋源区有自下向上的动能传输，另外，西风急流出口的平均动能转化增加，使得高层动能累积并向外辐散，从而对下游产生遥相关作用。通过CAM5.1模式模拟研究了北大西洋“三极子型”和“马鞍型”两种海温模态下的波作用通量传播特征，结果较好地验证了来自北大西洋的波动作用通量传播呈“SRP”型和“EU”型两种特征，对应的降雪分布表明两种模态下气候场要素的变化与对应雪深模态的分布特征一致。
关键词:春季欧亚积雪/
北大西洋海温/
三极子型/
马鞍型/
能量分析
Abstract:On the basis of the daily snow depth (SD) data provided by the Japanese 55-year Reanalysis project, the global reanalysis data from the European Centre for Medium-Range Weather Forecasts and sea temperature data from Hadley Center (Hadley), this study analyzes the asymmetric modes of the spring SD anomaly in Eurasia and its teleconnection with the North Atlantic sea surface temperature (SST). Results are verified by numerical simulation analysis. Significant differences are found between the first two spring SD modes over the Eurasian continent that are represented as two asymmetric forms in this study: the first mode features a zonal uniform distribution, and the second displays an obvious west–east contrast distribution. North Atlantic “tri-polar” and “saddle” SST modes have a significant correlation with the first and second SD modes, respectively. Corresponding to the two SST modes, the wave activity fluxes in the mid-high latitudes over the northern hemisphere are characterized by two kinds of propagation characteristics: Silk Road pattern (SRP) and Eurasian teleconnection pattern (EU), both of which have different effects on the position and intensity of the westerly air flow in middle–high latitudes, and thus exert different remote influences on the SD distribution in Eurasia. The localized multiscale energy and vorticity analysis shows that the kinetic energy (KE) of source region in the North Atlantic has a transform process from bottom to top. In addition, the average KE conversions enhance over the exit region of the westerly jet, benefiting high-level KE accumulation and outward divergence and creating remote effects on downstream areas. The CAM5.1 model simulation is used to study the effects of the two SST modes on the propagation characteristics of wave activity fluxes. Simulation results verify the observation results well. SST modes may be responsible for the SRP and EU propagation characteristics of wave activity fluxes. Meanwhile, changes in the climatic field elements of the two SST modes are consistent with the distribution characteristics of the corresponding SD modes.
Key words:Spring Eurasian snow depth/
North Atlantic sea surface temperature/
North Atlantic tri-pole/
North Atlantic saddle/
Energy analysis
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