台湾东北海域夏季冷穹及上升流的数值模拟
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摘要
夏季,黑潮在台湾东北向东海陆架的入侵表现为黑潮次表层水的强烈涌升,并在陆架上形成明显的冷穹。本研究利用ROMS(Regional Ocean Modeling System)模式,模拟了夏季黑潮入侵所形成的冷穹及上升流的三维结构,并讨论了上升流形成的动力机制。结果表明,冷穹中心在50m以上的深度位于25.5°N,122.5°E附近,最大降温5℃以上;在50m以下的深度,冷穹的中心位于台湾岛北缘。表层黑潮在台湾北缘不存在明显入侵,在陆坡东向转向附近则以气旋式环流入侵至陆架以上。此外,上升流主要位于陆坡坡度最大的区域,且黑潮次表层水的涌升存在两个较为明显的路径,分别位于台湾岛以北的100m与200m等深线之间以及东向转向的陆坡区域。在上层,平流作用是上升流产生的主要机制;而在近底层,平流作用与底摩擦都对上升流有贡献。
The Kuroshio on-shelf intrusion northeast of Taiwan manifests as the subsurface Kuroshio water upwelling and a "cold dome" structure in summer.Using ROMS(Regional Ocean Modeling System)model,the three-dimensional structure of the cold dome and the circulation along with upwelling induced by Kuroshio intrusion were analyzed,and the mechanisms of the formation of upwelling were also discussed.Model results show that the center of the cold dome is located near 25.5°N,122.5°E in the layers upper of 50 m with maximum 5 ℃cooling,and close to the north end of Taiwan Island in the layers lower of 50 m.The result of current structures show that Kuroshio surface intrusion is not obvious at the north end of Taiwan Island.A cyclonic circulation exists near the region where the shelf break turns eastward.Upwelling mainly occurs near the large slope of shelf break,with two obvious routes of the subsurface water upwelled onto the shelf.One of the routes is north of the Taiwan Island and between the isobaths of 100 m and 200m,while the other one is near the region where the shelf break turns eastward.In the upper layer,the advection term is the main dynamical factor of the upwelling.While in the near-bottom layer,both the advection and bottom friction terms contribute to the upwelling.
The Kuroshio on-shelf intrusion northeast of Taiwan manifests as the subsurface Kuroshio water upwelling and a "cold dome" structure in summer.Using ROMS(Regional Ocean Modeling System)model,the three-dimensional structure of the cold dome and the circulation along with upwelling induced by Kuroshio intrusion were analyzed,and the mechanisms of the formation of upwelling were also discussed.Model results show that the center of the cold dome is located near 25.5°N,122.5°E in the layers upper of 50 m with maximum 5 ℃cooling,and close to the north end of Taiwan Island in the layers lower of 50 m.The result of current structures show that Kuroshio surface intrusion is not obvious at the north end of Taiwan Island.A cyclonic circulation exists near the region where the shelf break turns eastward.Upwelling mainly occurs near the large slope of shelf break,with two obvious routes of the subsurface water upwelled onto the shelf.One of the routes is north of the Taiwan Island and between the isobaths of 100 m and 200m,while the other one is near the region where the shelf break turns eastward.In the upper layer,the advection term is the main dynamical factor of the upwelling.While in the near-bottom layer,both the advection and bottom friction terms contribute to the upwelling.
引文
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[24]CHASSIGNET E P,HURLBURT H E,SMEDSTAD O M,et al.The HYCOM(hybrid coordinate ocean model)data assimilative system[J].Journal of Marine Systems,2007,65(1):60-83.
[25]CHAO S Y.Circulation of the East China Sea,a numerical study[J].Journal of the Oceanographical Society of Japan,1990,46(6):273-295.
[26]CHEN H T,YAN X H,SHAW P T,et al.A numerical simulation of wind stress and topographic effects on the Kuroshio current path near Taiwan[J].J Phys Oceanogr,1996,26(9):1 769-1 802.
[27]PASCUAL A,GOMIS D,HANEY R L,et al.A quasigeostrophic analysis of a meander in the Palamos Canyon:Vertical velocity,geopotential tendency,and a relocation technique[J].Journal of Physical Oceanography,2004,34(10):2 274-2 287.
[28]HUTHNANCE J M.Circulation,exchange and water masses at the ocean margin:The role of physical processes at the shelf edge[J].Progress in Oceanography,1995,35(4):353-431.
[29]YANG D,YIN B,LIU Z,et al.Numerical study on the pattern and origins of Kuroshio branches in the bottom water of southern East China Sea in summer[J].Journal of Geophysical Research:Oceans,2012,117(C2):C02014.
[30]PEDLOSKY J.Geophysical fluid dynamics[M].New York:Springer,1979.
[31]OKE P R,MIDDLETON J H.Topographically induced upwelling off Eastern Australia[J].Journal of Physical Oceanography,2000,30(3):512-531.
[2]SU Ji-lan,PAN Yu-qiu.Preliminary study on the circulation dynamics of the shelf north of Taiwan[J].Acta Oceanologica Sinica,1989,11(1):1-14.苏纪兰,潘玉球.台湾以北陆架环流动力学初步研究[J].海洋学报,1989,11(1):1-14.
[3]HSUEH Y,CHERN C S,WANG J.Blocking of the Kuroshio by the continental shelf Northeast of Taiwan[J].Journal of Geophysical Research,1993,98(C7):12 351-12 359.
[4]LIU X,DONG C,CHEN D,et al.The pattern and variability of winter Kuroshio intrusion northeast of Taiwan[J].Journal Geophysical Research,2014,119(8):5 380-5 394.
[5]LIU X,CHEN D,DONG C,et al.Variation of the Kuroshio intrusion pathways northeast of Taiwan using the Lagrangian method[J].Science China:Earth Sciences,2016,59(2):268-280.
[6]TSENG W Y.On Copepoda of the family candaciidae in the northeast of sea-waters of Taiwan[C]//Proceeding of the 2nd CSKSymposium.Tokyo,1972:245-259.
[7]YIN F.Preliminary study of cold water mass near N.N.E.of Taiwan[J].Acta Oceanographica Taiwanica,1973,3(1):157-180.
[8]FAN K L.On upwelling off northeastern shore of Taiwan[J].Acta Oceanographica Taiwanica,1980,11(1):105-117.
[9]CHERN C S,WANG J.On the mixing of waters at a northern offshore area of Taiwan,Terrestrial[J].Atmospheric and Oceanic Sciences,1990(1):297-306.
[10]TANG T Y,TAI J H,YANG Y J.The flow pattern north of Taiwan and the migration of the Kuroshio[J].Continental Shelf Research,2000,20(4):349-371.
[11]WU C R,LU H F,CHAO S Y.A numerical study on the formation of upwelling off northeast Taiwan[J].Journal Geophysical Research,2008,113(C8):328-340.DOI:10.1029/2007JC004697.
[12]JAN S,CHEN C C,TSAI Y L,et al.Mean structure and variability of the cold dome northeast of Taiwan[J].Oceanography,2011,24(4):100-109.
[13]LIANG Xiang-san,SU Ji-lan.A two-layer model for the circulation of the East China Sea[J].Donghai Marine Science,1994,12(1):1-20.梁湘三,苏纪兰.东海环流的一个两层模式[J].东海海洋,1994,12(1):1-20.
[14]SU Ji-lan.A review of circulation dynamics of the coastal oceans near China[J].Acta Oceanologica Sinica,2001,23(4):1-16.苏纪兰.中国近海的环流动力机制研究[J].海洋学报,2001,23(4):1-16.
[15]GUO X,MIYAZAWA Y,YAMAGATA T.The Kuroshio onshore intrusion along the shelf break of the East China Sea:The Origin of the Tsushima Warm Current[J].Journal of Physical Oceanography,2006,36(12):2 205-2 231.
[16]CHANG Y L,WU C R,OEY L Y.Bimodal behavior of the seasonal upwelling off the northeastern coast of Taiwan[J].Journal of Geophysical Research:Oceans,2009,114(C3):C03027.
[17]SHCHEPETKIN A,MCWILLIAMS J.A method for computing horizontal pressure-gradient force in an oceanic model with a nonaligned vertical coordinate[J].Journal of Geophysical Research,2003,108(C3):3 090.
[18]SHCHEPETKIN A,MCWILLIAMS J.The Regional Ocean Modeling System:A split-explicit,free-surface,topography following coordinates ocean model[J].Ocean Modelling,2005,9(4):347-404.
[19]DONG C,IDICA E,MCWILLIAMS J.Circulation and multiple-scale variability in the Southern California Bight[J].Progress in Oceanography,2009,82(3):168-190,DOI:10.1016/j.pocean.2009.07005.
[20]YANG D,YIN B,LIU Z,et al.Numerical study of the ocean circulation on the East China Sea shelf and a Kuroshio bottom branch northeast of Taiwan in summer[J].Journal of Geophysical Research:Oceans,2011,116(C5):C05015.
[21]MELLOR G,YAMADA T.Development of a turbulence closure model for geophysical fluid problems[J].Review of Geophysical Space Physics,1982,20(4):851-875.
[22]RICCIARDULLI L,WENTZ F.Reprocessed QuikSCAT(V04)Wind Vectors with Ku-2011Geophysical Model Function,technical report number 043011[R].CA,USA:Remote Sensing Systems Technical Report,2011:8.
[23]Da SILVA A M,YOUNG C C,LEVITUS S.Atlas of surface marine data 1994,Vol.4:Anomalies of fresh water fluxes[M]//BROWN R H,BAKER D J,WINOKUR R S.NOAAAtlas NESDIS9.Washington DC:U.S.Dept.of Commerce,1994:308.
[24]CHASSIGNET E P,HURLBURT H E,SMEDSTAD O M,et al.The HYCOM(hybrid coordinate ocean model)data assimilative system[J].Journal of Marine Systems,2007,65(1):60-83.
[25]CHAO S Y.Circulation of the East China Sea,a numerical study[J].Journal of the Oceanographical Society of Japan,1990,46(6):273-295.
[26]CHEN H T,YAN X H,SHAW P T,et al.A numerical simulation of wind stress and topographic effects on the Kuroshio current path near Taiwan[J].J Phys Oceanogr,1996,26(9):1 769-1 802.
[27]PASCUAL A,GOMIS D,HANEY R L,et al.A quasigeostrophic analysis of a meander in the Palamos Canyon:Vertical velocity,geopotential tendency,and a relocation technique[J].Journal of Physical Oceanography,2004,34(10):2 274-2 287.
[28]HUTHNANCE J M.Circulation,exchange and water masses at the ocean margin:The role of physical processes at the shelf edge[J].Progress in Oceanography,1995,35(4):353-431.
[29]YANG D,YIN B,LIU Z,et al.Numerical study on the pattern and origins of Kuroshio branches in the bottom water of southern East China Sea in summer[J].Journal of Geophysical Research:Oceans,2012,117(C2):C02014.
[30]PEDLOSKY J.Geophysical fluid dynamics[M].New York:Springer,1979.
[31]OKE P R,MIDDLETON J H.Topographically induced upwelling off Eastern Australia[J].Journal of Physical Oceanography,2000,30(3):512-531.