热带西太平洋北赤道逆流区涡旋统计分析
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摘要
随着海洋技术的发展,中尺度的海洋过程越来越多的被揭示,中尺度涡旋作为重要的中尺度海洋过程,已经被大量的研究。但对于热带西北太平洋海区,中尺度涡旋特征的空间分布、季节变化以及移动规律等方面的研究还有所欠缺。本文使用Chelton提供的涡旋数据集,统计分析了热带西北太平洋海区涡旋特征的空间分布,发现以往研究较少的北赤道逆流(North Equatorial Countercurrent,NECC)区(A海区,120°~180°E,4°~6°N)较临近海域生成涡旋数量更多,涡旋半径、振幅、生命周期及非线性强度更大,移动距离更远,并且A海区涡旋经向移动距离服从伽马分布。涡旋在靠近西边界的区域更易向南移动,而在西边界以东的区域更易向北移动。A海区涡旋的生成数量具有明显的季节变化,主要受到流场剪切强度的影响。同时ENSO会对该区涡旋生成产生影响,其影响机制需要进一步的研究。
With the development of ocean technology,more and more mesoscale ocean processes have been revealed.Mesoscale eddies are an important mesoscale ocean process that has been the subject of much research in recent decades.However,research on the spatial distribution,seasonal variation,and movement characteristics of mesoscale eddies in the northwestern Pacific is lacking.In this paper,we statistically analyzed the spatial distribution of eddies in the northwestern tropical Pacific using the eddy dataset provided by Chelton.We found that more eddies are generated in the North Equatorial Countercurrent(NECC) area(A zone,120°–180°E,4°–6°N) where less research effort has been focused.Moreover,the eddy radii,amplitudes,lifecycles,and nonlinear intensities are larger,the movement distances are farther,and the meridional eddy movement distances obey a gamma distribution in the A zone.Most eddies move southward in the region close to the western boundary,and most move northward far away from the western boundary.The quantity of eddies generated in the A zone exhibits obvious seasonal variation,which is mainly affected by the shear intensity of the currents.At the same time,eddy formation is affected by the ENSO in this area,and its mechanism requires further study.
With the development of ocean technology,more and more mesoscale ocean processes have been revealed.Mesoscale eddies are an important mesoscale ocean process that has been the subject of much research in recent decades.However,research on the spatial distribution,seasonal variation,and movement characteristics of mesoscale eddies in the northwestern Pacific is lacking.In this paper,we statistically analyzed the spatial distribution of eddies in the northwestern tropical Pacific using the eddy dataset provided by Chelton.We found that more eddies are generated in the North Equatorial Countercurrent(NECC) area(A zone,120°–180°E,4°–6°N) where less research effort has been focused.Moreover,the eddy radii,amplitudes,lifecycles,and nonlinear intensities are larger,the movement distances are farther,and the meridional eddy movement distances obey a gamma distribution in the A zone.Most eddies move southward in the region close to the western boundary,and most move northward far away from the western boundary.The quantity of eddies generated in the A zone exhibits obvious seasonal variation,which is mainly affected by the shear intensity of the currents.At the same time,eddy formation is affected by the ENSO in this area,and its mechanism requires further study.
引文
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[13]Chen X,Qiu B,Chen S,et al.Seasonal eddy kinetic energy modulations along the North Equatorial Countercurrent in the western Pacific[J].Journal of Geophysical Research Oceans,2015,120(9):6351-6362.
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[16]Hsin Y C,Qiu B.Seasonal fluctuations of the surface North Equatorial Countercurrent(NECC)across the Pacific basin[J].Journal of Geophysical Research Oceans,2012,117(C6):6001.
[17]Chelton D B,Schlax M G,Samelson R M.Global observations of nonlinear mesoscale eddies[J].Progress in Oceanography,2011,91(2):167-216.
[18]Pedlosky J.Geophysical fluid dynamics[M].2nd ed.New York:Springer-Verlag,1987:710.
[19]Melnichenko O,Hacker P,Maximenko N,et al.Optimum interpolation analysis of Aquarius sea surface salinity[J].Journal of Geophysical Research Oceans,2016,121(1):602-616.
[2]Lukas R,Yamagata T,Mccreary J P.Pacific low-latitude western boundary currents and the Indonesian throughflow[J].Journal of Geophysical Research Atmospheres,1996,1011(C5):12209-12216.
[3]Hu D,Wu L,Cai W,et al.Pacific western boundary currents and their roles in climate[J].Nature,2015,522(7556):299-308.
[4]Qu T,Lukas R.The Bifurcation of the North Equatorial Current in the Pacific[J].Journal of Physical Oceanography,2003,33(1):5-18.
[5]Wang F,Song L,Li Y,et al.Semi annually alternating exchange of intermediate waters east of the Philippines[J].Geophysical Research Letters,2016,43(13):7059-7065.
[6]Lee S K.On the structure of supercritical western boundary currents[J].Dynamics of Atmospheres&Oceans,2001,33(4):303-319.
[7]Wyrtki K.The thermohaline circulation in relation to the general circulation in the oceans[J].Deep Sea Research,1961,8(1):39-64.
[8]Lukas R,Firing E,Hacker P,et al.Observations of the Mindanao Current during the western equatorial Pacific Ocean circulation study[J].Journal of Geophysical Research Atmospheres,1991,96(C4):7089-7104.
[9]Zhao J,Li Y,Wang F.Dynamical responses of the west Pacific North Equatorial Countercurrent(NECC)system to El Ni?o events[J].Journal of Geophysical Research Oceans,2013,118(6):2828-2844.
[10]Zhao J,Li Y,Wang F.Seasonal variation of the surface North Equatorial Countercurrent(NECC)in the western Pacific Ocean[J].Chinese Journal of Oceanology and Limnology,2016,34(6):1332-1346.
[11]Heron S F,Metzger E J,Skirving W J.Seasonal variations of the ocean surface circulation in the vicinity of Palau[J].Journal of Oceanography,2006,62(4):413-426.
[12]Chen L,Jia Y,Liu Q.Mesoscale eddies in the Mindanao Dome region[J].Journal of Oceanography,2014,71(1):133-140.
[13]Chen X,Qiu B,Chen S,et al.Seasonal eddy kinetic energy modulations along the North Equatorial Countercurrent in the western Pacific[J].Journal of Geophysical Research Oceans,2015,120(9):6351-6362.
[14]Early J J,Samelson R M,Chelton D B.The Evolution and Propagation of Quasigeostrophic Ocean Eddies[J].Journal of Physical Oceanography,2011,41(8):1535-1555.
[15]Zhang Z,Wang W,Qiu B.Oceanic mass transport by mesoscale eddies[J].Science,2014,345(6194):322-324.
[16]Hsin Y C,Qiu B.Seasonal fluctuations of the surface North Equatorial Countercurrent(NECC)across the Pacific basin[J].Journal of Geophysical Research Oceans,2012,117(C6):6001.
[17]Chelton D B,Schlax M G,Samelson R M.Global observations of nonlinear mesoscale eddies[J].Progress in Oceanography,2011,91(2):167-216.
[18]Pedlosky J.Geophysical fluid dynamics[M].2nd ed.New York:Springer-Verlag,1987:710.
[19]Melnichenko O,Hacker P,Maximenko N,et al.Optimum interpolation analysis of Aquarius sea surface salinity[J].Journal of Geophysical Research Oceans,2016,121(1):602-616.