【作者】 刘传玉；

【导师】 王凡；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 物理海洋学， 2009， 博士

【摘要】 海洋锋面既是各种物理过程,如环流、上升流、混合等的结果,也是这些物理过程的指标,还是影响流场结构、海洋热量和动量交换、海气相互作用以及生物化学过程的重要因素。同时,海洋锋面研究还与海洋产业活动,如海洋渔业、环境保护、海洋倾废等密切相关,也是军事海洋学必须考虑的问题。所以,海洋锋面的研究也成为物理海洋学和海洋交叉学科研究中的一个重要内容。本研究以中国东部近海(渤海、黄海、东海及南海北部)锋面的分布特征、变化规律、动力机制及对相应过程的影响为研究对象,以1985~2002年AVHRR Pathfinder的卫星海表面温度数据为基础,辅以POM模式,通过数据分析、模式验证和动力机制分析相结合的方法,既全面描述了中国东部近海锋面分布和变化的总体特征,又深入研究了三个典型锋面,即南黄海西部沿岸锋面、黄海暖流源区陆架锋面和东海黑潮陆坡锋面的具体特点,结果如下:1,中国东部近海温度锋面分布状况的季节变化明显。冬季,锋面丰富,形状规则,位置稳定,可以明确区分出14条沿岸流锋面和暖流锋面。春季及夏初,锋区分布范围广,没有规则的锋面形态,也没有固定的发生区域,不能明确分辨出具体锋面,锋区大体按黑潮流域—长江河口沿岸区域—南黄海区域的方向和渤海—北黄海—南黄海的方向转移。夏季在沿岸区域产生潮汐锋,秋季则很少有锋面出现。对于冬季锋面的位置来讲,沿岸锋面的年际变化小,暖流锋面的年际变化大;受地形限制的锋面年际变化小,脱离地形控制的锋面年际变化大。2,冬季山东半岛南部(即南黄海西部)温度锋面的完整形态为“N”形,东、西两部分平行岸线和等深线,中间部分跨越等深线。表层以下的黄海沿岸流和黄海暖流及分支是此锋面生成和维持的直接原因:南下沿岸流与北上的黄海暖流形成了锋面的东部部分,反气旋性回流的沿岸流与被沿岸流挟入南黄海西部的黄海暖流暖水及进入南黄海西部的黄海暖流分支形成了锋面的中部和西部部分。通过强烈的垂直混合,此锋面形态特征从表层以下传播到表层。沿岸流和暖流的强弱会影响此锋面的位置,锋面的形成会反过来影响上述流态。冬季风是维持相关环流和锋面结构的间接原因。3,暖舌西移和双暖舌温度结构是冬季南黄海温度分布的主要特征,黄海暖流源区暖舌南北两侧形成的双锋面是南黄海锋面结构的主要特征,这两条锋面有时也可在西端连为一体,形成环绕黄海暖水舌前锋区的弧形锋面。南侧锋面大致沿长江浅滩边缘,北侧锋面大致呈东西走向,横跨黄海海槽入口,在此锋面的阻挡下,黄海暖舌无法沿海槽中央北上,在两锋面之间沿着黄海海槽西侧进入黄海。统计结果表明,北侧锋面的位置、强度变化,是驱使暖舌沿海槽西侧进入黄海、并控制其西移程度的主要因素。当北侧锋面偏南或强度大时,暖舌西移程度大,当两条锋面间隔距离大时,暖舌的西移程度弱,暖舌主体北侵的程度就越大,双暖舌结构越不明显。源区黄海暖流的东西向质量和热量输运,黄海内部的风应力等通过影响锋面的位置和强度而间接影响暖舌西移程度。黄海暖舌甚至黄海暖流的起源值得进一步探讨。4,东海黑潮锋在台湾岛东北部和九州岛西南部的平均经向位置之间存在着反位相的年际变化规律。长期观测资料和数值试验结果都表明,进入东海的黑潮流量的改变能够导致黑潮锋面位置在两地反位相的变化:当黑潮流量增大时,黑潮在台湾岛东北部的向陆架入侵减小,锋面向南偏移,而同时黑潮在九州岛西南部的向陆架入侵增大,锋面向北偏移;冬季风应力在台湾岛东北部以东北风为主,在九州岛西南部以西北风为主。当风应力增大时,黑潮锋面在台湾岛东北部向西北偏移,在九州岛西南部向西南方向偏移。黑潮流轴位置的改变也可能是导致反位相变化的原因。位涡输运方程中的地形和斜压联合效应项以及风应力项(主要是Ekman输运)在两地的不同表现可能是控制这种变化的机制。更多还原

【Abstract】 Oceanic fronts are results and indicators of the physical processes, such as currents, upwellings and vertical mixing. Oceanic fronts can influence the circulation pattern, the exchange in water masses and heat, the interaction of air-sea, the bio-chemical processes and the propagation characteristics of the sound. Thus, oceanic front becomes one of the key points in the physical oceanography and also in the inter-disciplinary studies.Based on the AVHRR Pathfinder satellite SST data from 1985 through 2002 and simulation results from POM, the dissertation focuses on the distribution, variation, dynamical mechamism and the environmental effects of thermal fronts in the eastern China Seas (eCS, including the Bohai Sea, the Yellow Sea (YS), the East China Sea (ECS) and the northern South China Sea). The dissertation firstly describes the distribution and variations of fronts in the eCS as a whole, and then investigates 3 typical fronts, say, a coastal front in the western South YS, a continental shelf front in the Yellow Sea Warm Current (YSWC) origin area and a shelf-break front (the Kuroshio front) in the ECS.Fronts in the eCS show clear seasonal variations: in wintertime, 14 main fronts including warm current fronts and coastal current fronts are clearly distinguished; in spring, the eCS shows irregular frontal zones with high intensity and gradual shift from the Kuroshio domain to middle YS; in summertime, the upwelling fronts and the tidal fronts occur in coastal areas. In fall, few fronts can be distinguished. For fronts in wintertime, those generated mainly by warm currents or less influenced by the bathymetric topography show large interannual variations while those generated mainly by coastal currents or controlled by the bathymetric topography show weak interannual variations.The N-shape front in the western YS in winter composes of a west and an east wings roughly along the northeast-southwestward isobaths with a southeastward middle segment across isobaths of 20~50 meters. Numerical simulation reveals that a cold coastal jet flowing anticyclonicaly below the 10 m depth after bypassing the Shandong Peninsula and the cold water penetrates southward into the western South YS. On the south, warmer water from a northwestward YSWC branch and from the northward YSWC also intrude into the western South YS. The N-shape front forms between the cold water and the surrounded warm water, and then it extends upwards to the surface through vertical advection and mixing.The SST climatology in winter clearly shows a westward shifted warm tongue originating from the YSWC origin area. Strong fronts occur on both northern (hereafter YF-N) and southern (YF-S) sides of the warm tongue. The strong interannual variation of the westward shift shows positive relation with the SST in the entire YSWC domain, indicating the shift originates from the YSWC origin area. The westward shift of the warm tongue and the meridional location of the YF-N show strong relationship: the more southward or stronger the Y-NF, the more westward of the warm tongue, indicating the later blockes the YSWC from flowing northward along the YS trough and induces the YSWC to flow northwestward. Significant relation is found between the meridional location of YF-N and cold water in the South YS interior while weak relations are shown between the location of YF-N and the local wind, the cold water in the YS interior as well as the strength of the YSWC. The cold water in the South YS interior may influence the westward shift through influencing the YF-N. Thus, we believe that the location and strength of the YF-N are important factors in generating and controlling the westward shift of the warm tongue. SST and altimetry data also show a possible connection between the Taiwan Warm Current and the variations of the YSWC thermal structures.The Kuroshio Front shows anti-phase interannual variations between areas of northeast of Taiwan and southwest of Kyushu. The anti-phase variations show good relationship with the observational data of the Kuroshio transport and the wind stress magnitude. When the Kuroshio transport decreases along the PN section or when wind stress increases in the middle ECS, the amplitude of the interannual variation increases. Numerical simulation results from case tests further demonstrate these relations. The balance between the transport of potential vorticity, the wind stress curl and the joint effect of baroclinic and bottom release may control the intrusion degrees of the Kuroshio onto the shelf. Thus, differences between the balance patterns in the two areas may be the possible reasons for the anti-phase interannual variation.更多还原