太平洋中纬度不同区域气旋式暖涡和反气旋式冷涡的结构研究

STRUCTURES OF“ABNORMAL”EDDIES IN DIFFERENT REGIONS OF THE MID-LATITUDE PACIFIC OCEAN

作为海洋中重要的物理现象,气旋(反气旋)中尺度涡通常被认为会在海表产生冷(暖)异常,但海洋中还存在着相当数量具有“异常”海表温度的涡旋,即气旋式暖涡和反气旋式冷涡,为研究这一类“异常”涡旋的结构特征,利用2000~2020年的卫星遥感数据和Argo剖面数据,对太平洋及四个中纬度特征区域的常规涡旋(气旋式冷涡、反气旋式暖涡)和“异常”涡旋进行了表面和垂直温度异常结构的合成和对比分析。结果表明:(1)太平洋区域约有11%的反气旋涡为反气旋式暖涡,约9%的气旋涡为气旋式冷涡,“异常”温度层存在于50 m以浅;“异常”涡旋在归一化涡旋半径内具有与常规涡旋相反的海表面温度异常合成结构,且引起的异常大小要弱于常规涡旋;(2)黑潮延伸体区域“异常”涡旋的海表面温度异常结构为偶极子模态,与常规涡旋及其他三个区域涡旋差别最大。在垂向上,不同区域“异常”涡旋的结构差异主要体现在“异常”温度层的厚度、核心深度和强度上;(3)具有次表层强化特征的“异常”涡旋,可能主要由涡旋抽吸和涡致Ekman抽吸诱导形成;具有表层强化特征的“异常”涡旋可能主要由涡致Ekman抽吸诱导形成。此外,涡旋的水平搅拌机制在一些区域也起到了比较重要的作用。上述研究结果对于理解海洋“异常”涡旋现象、分析其生成和动力机制有一定的参考价值和科学意义。

As a crucial physical phenomenon in the ocean,cyclonic(anticyclonic)eddies are generally thought to generate cold(warm)sea surface anomaly.However,there are a considerable number of eddies with“abnormal”sea surface temperature,which called anticyclonic cold eddies and cyclonic warm eddies.This study focus on the structural characteristics of the“abnormal”eddies,based on satellite remote sensing data and Argo profile data from 2000 to 2020,the composite structure of temperature anomalies of normal eddies(cyclonic cold eddies,anticyclonic warm eddies)and“abnormal”eddies in the Pacific Ocean and four mid-latitude characteristic regions were analyzed in a comparative manner.Results show that first,about 11%of the anticyclonic eddies in the Pacific Ocean are anticyclonic warm eddies,and about 9%of the cyclonic eddies are cyclonic cold eddies,and the“abnormal”temperature layer exists in the depth shallower than 50 m.The synthetic structure of sea surface temperature anomalies of“abnormal”eddies is the opposite of the normal eddies within the normalized eddy radius,and the degree of temperature anomalies is weaker than that of the normal eddies.Secondly,the sea surface temperature anomalies of the“abnormal”eddies in the Kuroshio Extension region have dipole modes,which is the most different from those of the normal eddies and the other three regional eddies.In vertical direction,the structural differences of the“abnormal”eddies in different regions are shown mainly in the thickness,core depth,and strength of the“abnormal”temperature layer.Thirdly,the“abnormal”eddies with subsurface strengthening characteristics may be formed mainly by eddy pumping and eddy-induced Ekman pumping;and the“abnormal”eddies with surface strengthening characteristics may be formed by mainly eddy-induced Ekman pumping.Lastly,horizontal eddy stirring plays an important role in some regions.This study provides a reference in scientific significance for understanding the phenomenon of“abnormal”eddies and analyzing their generation and dynamical mechanisms.