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题名: 北太平洋低纬度西边界流的时空特征和变异规律研究
作者: 李琦
学位类别: 博士
答辩日期: 2009-05-25
授予单位: 中国科学院海洋研究所
授予地点: 海洋研究所
关键词: 北太平洋 ; 低纬度西边界流 ; 北赤道流分叉 ; ENSO
中文摘要: 北太平洋低纬度西边界流连接着太平洋热带环流和副热带环流,对于世界大洋经向质量、热量和盐量输送起着重要的作用,对北赤道流(NEC)、源区黑潮(KC)和棉兰老流(MC)的时空特征和变异规律进行研究,对认识北太平洋西边界流海洋在全球气候系统中的作用具有重要的理论和实践意义。 本文利用1957-2006年共50年的涡解高分辨率OFES(OGCM for the Earth Simulator)海洋模式资料,对北太平洋低纬度西边界流的时空特征和变异规律进行了分析,结果表明: (1)涡解高分辨率的OFES模式数据结果较SODA能更好地刻画NMK流系三维空间结构的分布特征;黑潮源区涡结构的变化,MUC、 LUC及NEC下的东向流也得到了较好的刻画;其空间结构与实测结果相吻合。 (2)北太平洋低纬度西边界流NMK流系流量具有明显的季节、年际和年代际变化,NEC、KC和MC流量的变化周期频谱较宽,主要为3-6个月的季节振荡和2-7年左右ENSO尺度周期以及10年以上周期的年代际变化。MC主要表现为准两年周期振荡。 (3)NEC、MC流量变化表现为单峰型分布,春季最大(5月),秋季最小(11月);KC流量的变化为双峰型,大值出现在春季和夏末秋初,春季最大(4月),秋季次之,冬季最小(1月)。在季节时间尺度上,NEC、MC流量同相变化,除冬季外,KC与MC输运反向。 (4) 在年际时间尺度上,受北赤道流流量变化的影响,NEC与KC、MC流量之间为正相关关系;KC与MC分配量(北赤道流向北、向南的经向分配量)之间则为强的负相关关系,其年际异常变化与NEC分叉位置的变化和冷、暖ENSO事件发生密切相关。分叉位置偏北(南)时,KC分配量小(大)而MC分配量大(小);在El Nino年,KC分配量小,MC分配量大,La Nina年情况则刚好相反。 (5)在年代际时间尺度上,在70年代末气候跃变以后,NEC、KC和MC流量明显减少,NMK环流系统减弱。NEC的减弱主要受上世纪80年代以后ENSO暖事件发生频率和强度的增加所影响,而KC和MC的减弱则主要受NEC减弱控制。同时发现,NEC分叉位置存有明显的年代际变化,在气候跃变以后有长期偏北的趋势,受其影响,与之相对应的是北赤道流向南经向分配量的增加和向北流量分配率的减少。 关键词:北太平洋,低纬度西边界流,北赤道流分叉,ENSO
英文摘要: As connecting the tropical and subtropical ocean circulations, North Pacific Low Latitude West Boundary Currents (NPLLWBC) play a very important role in the meridional transport of mass, heat and salt in the world ocean. Studies on the spatial and temporal characteristics of NPLLWBC as well as its mechanism are significant in practice. Spatial and temporal characteristics of NPLLWBC as well as its variation are analyzed by using fifty-year numerical outputs from high eddy-resolving simulations of OFES (OGCM for the Earth Simulator). The results are as follows. The characteristics of the spatial structure of the NMK systems can be well described by the OFES data compared to Simple Ocean Data Assimilation (SODA). The variability of the eddy structure in the source area of the Kuroshio, MUC, LUC and the eastward current under the NEC is well described, too. The spatial structure of the system and the flux are consistent with the observed data. The NEC, KC and MC transport have a strong seasonal, interannual and interdecadel signal. Spectrum analysis indicates that NMK transport chiefly has a seasonal oscillation with a three-month to six-month period, an interannual oscillation with 2a and 2-7a ENSO period and an interdecadal variation with a period more than 10 years. On the interannual scale, the frequency spectrum of the variation is rather broad. The NEC and KC transport is dominated by ENSO period with 2-7 years, and the MC transport is dominated by a quasi-biennial oscillation. The NEC and MC have a seasonal maximum transport in spring (May) and a minimum transport in fall (November). The KC has a maximum transport in spring (April), minimum in winter (January), and the fall takes the secondary. The NEC and the KC vary in the same phase, while the KC and MC vary in the contrary phase except in winter. On interannual timescale, the NEC is positive correlated to KC (MC). The NEC transport variation determines the KC and MC transport. The NMK transport is closely related with ENSO. The correlation between the distribution rates of the KC and MC transport is negative, which is affected by ENSO and NEC bifurcation latitude. When the El Nino happens, the NMK transport decreases, the bifurcation latitude moves northward, the distribution rates of the KC transport is less and the distribution rates of the MC transport is more. The situation is reversed while the La Nina happens. It has a larger influence on the NEC and KC transport than on the MC transport. The NMK transport decreases evidently after a step change at the end of the 70th decade of last century. NEC, KC and MC transports decrease obviously. The decrease is mainly account for the strengthened El Nino after the 80th decade. The decrease of the NEC transport determines the variation of the KC and MC transport. Besides, the NEC bifurcation latitude has a long trend of moving northward after climate change, with the distribution rate of KC and MC transport increases and decreases, respectively. Keyword: the North Pacific, Low Latitude West Boundary Current, NEC bifurcation latitude, ENSO
语种: 中文
内容类型: 学位论文
URI标识: http://ir.qdio.ac.cn/handle/337002/678
Appears in Collections:海洋环流与波动重点实验室_学位论文

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北太平洋低纬度西边界流的时空特征和变异规律研究.李琦[d].中国科学院海洋研究所,2009.20-25
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