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题名: 黑潮对中国近海的两处入侵和主要通道输送量的季节到年代际变化
作者: 李莎莎1
学位类别: 硕士
答辩日期: 2016-05-17
授予单位: 中国科学院大学
授予地点: 北京
导师: 齐鹏
关键词: 中国海 ; 黑潮入侵 ; 体积输送 ; 吕宋海峡 ; 台湾东北海域
学科分类: 地球科学
学位专业: 环境工程
中文摘要: 本文基于HYCOM和OFES模式输出的长序列格点数据以及WOA13资料研究黑潮在中国近海的两处入侵现象和主要通道输送量的季节到年代际变化。
黑潮水的一部分通过向中国近海的入侵,不仅改变中国近海陆架区的温盐分布和环流状况,还给陆架浅水区带来营养物质,从而促进海洋初级生产力。这是本文选题的学术价值和意义。本文在前人研究的基础上,利用浮标观测资料和模式输出数据分析黑潮在吕宋海峡海域和台湾东北海域的两处入侵现象。对吕宋海峡研究区做水团分析显示,该区各点的T-S点聚图均呈反S形分布,25.8等密度面是其分界面;该分界面以上,研究区海水的温盐特性介于南海水和黑潮水之间,并表现出显著的次表层高盐水特征;经度上位置越靠西的点越接近南海水的性质,越靠东的点越接近黑潮水的性质;纬度断面越靠近台湾岛南端其海水性质越向黑潮水靠拢,纬度断面靠近吕宋岛其海水性质则在南海水和黑潮水之间均匀分布。25.8等密度面以下,海水盐度自西向东逐渐减小。
为了解吕宋海峡上层体积输送(LST)的低频变化特征,我们利用涡分辨力海洋环流模式OFES的62年(1950~2011)后报输出得到LST不仅有约3年和7年显著的年际振荡,而且有约14年显著的年代际变化。为探究影响LST这些低频振荡特征的局地因子,我们首先分析了吕宋冷涡(LCE)活跃区上空风应力旋度(WSC)异常场主要模态的低频振荡特征。结果表明,对LCE活跃区上空WSC去除季节信号的异常场做EOF分析取得了典型的年际以上尺度的主要振荡特征,其第一模态时空变化表现为约14年显著的年代际振荡和WSC异常场正位相区年代际尺度上的南移,而第二模态表现为约3年显著的年际振荡和WSC异常场正位相区年际尺度上的北移。此外,LST约7年的变化特征可视为源区黑潮体积输送低频变化在该尺度上的印记。
台湾东北海域是黑潮进入东海与陆架水交换的主要的入侵区。对台湾东北海域距平流场做矢量EOF分析,得到该海域主要时空变化特征。其第一模态空间场主要体现了东海黑潮主流区的振荡和与其相伴随的在122.8°E附近跨200m等深线分布的气旋/反气旋式环流结构,代表了黑潮流经台湾东北海域时其侵入陆架部分与主流振荡之间的反位相关系,这和黑潮入侵东海陆架强度变化与黑潮主流强度变化之间的负相关关系是一致的。季节变化上,冬季在122.2°E附近表现为较强的入侵,夏季则不利于入侵。同时,第一模态也显示了一定的年际变化特征,例如,1995,1997,1999年夏季都是较弱的入侵年。不同于第一模态,第二模态则代表了黑潮主流区两侧的振荡和衍生出的台湾岛以北偏东海区的气旋/反气旋式环流结构。时间系数为正值时,黑潮主流摆动偏向陆架且能冲上200m等深线,但不利于黑潮向台湾岛北侧的入侵;时间系数为负值时,主流摆动偏向大洋,但有利于黑潮向台湾岛北侧的入侵。
东海各通道表层(0~60m)体积输送与东海海面风应力之间在季节变化上有相当好的一致性。首先,东海海面风应力距平场EOF第一模态表现为显著的东亚冬夏季节转换的季风特点,且没有什么年际变化:冬季东海各通道海域受东北风控制,在Ekman输送机制下有助于通过琉球各通道流入东海;夏季为西南风,有助于流出东海。同时,我们对各通道表层体积输送的EOF分析发现,其第一模态时间系数不仅有季节变化,其年际变化也比较明显;特别是,当对各通道整层体积输送进行EOF分析时,其季节变化不明显,而其年际变化更加明显。这说明风应力对琉球各通道体积输送的影响只体现在表层,其对整层的影响较弱,换言之,影响整层体积输送另有其它因子。例如,年际变化上,PDO可能对东海各通道体积输送的年际变化具有一定的调控作用,而ENSO对它的影响较弱。
英文摘要: Based on long term grid data from HYCOM and OFES model outputs, combined with the WOA13 data, this paper investigated two shelfward intrusions of the Kuroshio and seasonal to decadal variations of the volume transport in the main passages in China seas.
Shelfward intrusion of the Kuroshio not only affects the shelf temperature and salinity characteristics and the shelf circulation, offshore China, but also supply nutrients that enhance biological activity there. In this paper, based on previous researches, using buoy measurements and model outputs, we studied the two invasions in the Luzon Strait area and area off northeast Taiwan. We analyzed water mass properties of the Luzon Strait area and found that the T-S scatter diagram of each point in the study area shows inversed S-shaped structure, the isopycnal 25.8 is its interface; Above the interface, the temperature and salinity property of the study area is between the South China Sea water and the Kuroshio water, and shows significant characteristic of subsurface high salinity water. Positions closer to the west correspond to water mass characteristics closer to the South China Sea water; while positions closer to the east correspond to characteristics closer to the Kuroshio water. Latitude sections closer to the southern tip of Taiwan Island correspond to water mass properties closer to the Kuroshio water, while latitude sections near Luzon Island, the seawater property distributes uniformly between the South China Sea water and the Kuroshio water. Below the isopycnal 25.8, the salinity decreases from the west to the east.
In order to obtain low frequency variations of the upper-layer Luzon Strait volume transport (LST), we use the 62-year (1950~2011) hindcast outputs from an eddy-resolving ocean general circulation model revealed that LST has prominent interannual (roughly 3 years and 7 years) and decadal (roughly 14 years) variabilities. To seek local factors affecting the low frequency oscillation of LST, deseasonalized anomaly fields of wind stress curl(WSC) over the Luzon cold eddy(LCE) active area were then analyzed using empirical orthogonal function (EOF), and dominant EOF modes of WSC anomaly were achieved. Results show that spatio-temporal variability of the first EOF mode is of prominent decadal oscillation with period of roughly 14.2 years and decadal southward shift of positive phase of the WSC anomaly, while the second EOF mode is of interannual oscillation of roughly 3.3 years and interannual northward shift of positive phase of the WSC anomaly. In addition, the near 7-year noticeable interannual oscillation can be regarded as an imprint of the variability of Kuroshio volume transport at its origin.
Waters off northeast Taiwan is a major intrusion area after the Kuroshio flows into the East China Sea and exchanges with shelf water. We obtained major temporal and spatial variation characteristics by doing vector EOF analysis to the current field anomalies off northeast Taiwan. The spatial field of the first EOF mode mainly reflects the Kuroshio's mainstream oscillation accompanied with a cyclonic/anticyclonic circulation structure near 122.8°E across the 200m isobaths, which represents the anti-phase relationship between the Kuroshio mainstream oscillation and its invasion onto the shelf off northeast Taiwan. This is consistent with the negative correlation between the Kuroshio intensity change and its intrusion onto ECS shelf. Strong intrusion occurs near 122.2°E in winter, while weak or no intrusion in summer. Meanwhile, the first mode also shows the interannual characteristics, for example, invasions are extremely weak in summer of 1995, 1997 and 1999. Unlike the first mode, the second EOF mode represents oscillations on both sides of the Kuroshio mainstream and the accompanied cyclonic/anticyclonic circulation structure off north Taiwan. When time coefficients are positive, the Kuroshio mainstream swings towards the continental shelf and can rush onto the 200m isobaths, but it does not contribute to the shelfward intrusion off north Taiwan Island; when the time coefficient is negative, the Kuroshio mainstream swings towards ocean, and it is beneficial to the Kuroshio intrusion to the north shelf off the Taiwan Island.
There is a very good consistency between the seasonal variation of the surface-layer(0~60m) volume transport in the channels of the ECS and that of the surface wind stress. The first EOF mode of the ECS wind stress anomaly shows significant seasonal transition of East Asian monsoon between winter and summer, and there is almost no interannual change: since channel area along the Ryukyu Islands is controlled by northeasterly winds in winter, Ekman transport mechanism promotes flowing into the East China Sea through each channel; southwesterly winds in summer promotes flowing out of the ECS. At the same time, EOF analysis of channel transports of surface-layer integration indicates that the first mode time coefficient has not only seasonal but also interannual variations. In particular, EOF analysis of channel transports of entire-layer integration shows that its interannual variation is more significant than its seasonal one. This suggests that the wind stress field impacts the volume transport of each Ryukyu channel only in the surface layer, its impact on the whole layer is weak. In other words, there should be other factors affecting the entire-layer volume transport. For example, on interannual-scale variations, PDO may have certain modulation effect on the interannual variability of the volume transport of each channel in ECS, while the effect of ENSO is weak. 
语种: 中文
内容类型: 学位论文
URI标识: http://ir.qdio.ac.cn/handle/337002/112523
Appears in Collections:海洋环流与波动重点实验室_学位论文

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作者单位: 1.中国科学院海洋研究所
2.中国科学院大学

Recommended Citation:
李莎莎. 黑潮对中国近海的两处入侵和主要通道输送量的季节到年代际变化[D]. 北京. 中国科学院大学. 2016.
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