北太平洋副极地海洋锋四季变异特征及其与中纬度大气的联系

Seasonal variation characteristics of the subarctic front in North Pacific and its relationship with the mid-latitude atmosphere

中文关键词:  副极地海洋锋区，海温异常，四季变异，大气瞬变涡旋强迫，中纬度大气环流

英文关键词:Subarctic oceanic frontal zone, Sea temperature anomaly, Seasonal variability, Atmospheric transient eddy forcing, Mid-latitude atmospheric circulation

中文摘要:

      基于高分辨率海洋与大气再分析资料，结合统计分析与动力学诊断，阐释了北太平洋副极地海洋锋区（Subarctic Oceanic Frontal Zone, SAFZ）四季变异的特征及成因，揭示了与SAFZ四季异常相伴随的中纬度大气环流异常特征及其对应的动力学过程。结果表明，SAFZ从秋、冬到次年春季强度逐渐增强，夏季相对较弱。海温经向平流过程和海气界面净热通量交换过程是制约SAFZ强度季节变化的主要因子：前者对维持SAFZ秋、冬、春季强度较强起主导作用，后者对夏季SAFZ强度减弱起重要贡献。在不同季节，伴随SAFZ强度的变异，边界层湍流热通量发生变异，非绝热加热异常引起锋区上方低层气温经向梯度与大气斜压性异常，在大气瞬变涡旋涡度强迫主导的影响下，中纬度北太平洋及我国东部、东北部等地的上空伴随产生相当正压结构的大气位势高度场异常和风场异常。

英文摘要:

      Through statistical analysis and dynamical diagnosis, high-resolution oceanic and atmospheric reanalysis data are used to elucidate the characteristics and causes of seasonal variations of Subarctic Oceanic Frontal Zone (SAFZ) in the North Pacific, and to reveal the characteristics of mid-latitude atmospheric circulation anomalies associated with SAFZ’s seasonal variations and their corresponding dynamic processes. The results indicate that the SAFZ gradually strengthens from autumn and winter to the following spring, while being relatively weaker in summer. The meridional advection process of sea surface temperature (SST) and the net heat flux exchange process at the sea-air interface are the main factors constraining to the season variation of SAFZ’s intensity: The former factor plays a dominant role in maintaining a strong SAFZ during autumn, winter and spring, while the latter factor contributes significantly to the weakest SAFZ in summer. Accompanied by SAFZ’s intensity variabilities in different seasons, the boundary layer turbulence heat flux anomalies occur, and the diabatic heating anomalies lead to the anomalies of low-level atmospheric meridional temperature gradient and atmospheric baroclinicity above SAFZ. Due to the dominant influence of atmospheric transient eddy vorticity forcing, the equivalent barotropic structure anomalies of atmospheric geopotential height and wind field generate over the regions of mid-latitude North Pacific and Eastern and Northeastern China.