摘要:利用1981~2013年NOAA（美国国家大气海洋管理局）海温资料和NCEP（美国环境预报中心）大气再分析资料，采用经验正交函数（EOF）分解方法对850 hPa瞬变高度场进行分解发现：850 hPa瞬变高度场经验正交函数分解的前两模态表征同一发展型波动的传播特征，该波动在日本以西形成然后向东发展，沿东偏北移动，在日界线附近发展达到最强，之后迅速向东北衰弱直至消亡，本文将其定义为西部型天气尺度涡旋（WSE）。合成分析表明，西部型天气尺度涡旋的强弱变化与北太平洋大范围的海温、副极地海洋锋异常存在密切联系，当西部型天气尺度涡旋活动偏强时，北太平洋北部和中部的海温显著偏冷，副热带地区海温显著偏暖，副极地海洋锋大大增强。同时，西部型天气尺度涡旋的强度与大气环流异常存在明显的协同变化，表现为西部型天气尺度涡旋偏强对应于阿留申低压增强且位置偏东，中纬度上空纬向西风增强。海洋和大气环流的这种变化增强了西北太平洋上空大气的斜压性，使得有效位能向扰动动能的转换增加，从而有利于西部型天气尺度涡旋的发展。
关键词:天气尺度涡旋/
海洋锋/
大气环流/
协同变化
Abstract:Based on NOAA (National Oceanic and Atmospheric Administration) sea surface temperature (SST) dataset and NCEP (National Center for Environmental Prediction) reanalysis dataset during 1981-2013, the synoptic-scale transient geopotential height at 850 hPa is decomposed by using EOF (empirical orthogonal function). The results show that the first two leading EOF modes represent the propagation characteristics of the same developing synoptic-scale eddy. The synoptic-scale eddy forms to the west of Japan and develops while it moves along the northeast path. It reaches the strongest near the dateline and then weakens rapidly along its northeastward moving and eventually disappears. This eddy is defined as WSE (western synoptic-scale eddy) in the present study. The composite results show that the intensity of the WSE is closely linked with the SST and subpolar oceanic front anomalies in the North Pacific. When the WSE is strong, the SST is significantly colder in the northern and central North Pacific and warmer in the subtropical zone, and the subpolar oceanic front is robust. At the same time, the variation of the WSE is significantly coordinated with the atmospheric circulation anomaly. Corresponding to the strong WSE, the Aleutian-Low strengthens and shifts eastward, and the zonal westerly wind in the mid-latitude zone enhances. The above variations of oceanic and atmospheric circulations increase the atmospheric baroclinicity over the northwestern Pacific, leading to enhanced conversion from available potential energy to perturbation kinetic energy that is favorable for the WSE development.
Key words:Synoptic-scale eddy/
Oceanic front/
Atmospheric circulation/
Coordinated variation
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