夏末秋初秦皇岛海域水动力特征及对风的响应研究

发布时间：2018-07-13 14:02

【摘要】：秦皇岛海域是连接渤海的主要海湾——辽东湾与渤海湾的关键海域,是辽东湾与渤海中部及渤海湾进行物质和能量交换的重要通道。了解海域内水动力过程的变化规律和作用机理,对物质和能量的长期输运和交换、污染物的扩散和分布、海域自净能力以及海域生态环境修复的深入研究具有重要的意义。本文基于2013年9月在秦皇岛海域布放的4套座底式海床基观测系统获取的海流、水位和底层温度连续观测资料,结合同期数值风场和海表高分辨率温度场(SST)等数据,采用经典调和分析方法对夏秋季风转换期秦皇岛海域的潮流和余流特征进行了分析,并通过与辽东湾东侧海域研究结果的比较,研究辽东湾整体的潮流分布和环流形态,在此基础上对秦皇岛海域水动力要素对局地风场的响应进行探讨,最后利用小波分析方法从能量角度研究风场对余流和海浪的能量输入及能量在垂向上的传递方式。潮流特征研究结果显示:秦皇岛海域的潮流属于规则半日潮流,W1—W4站均处于浅水潮流区,浅水分潮显著。M2分潮流在秦皇岛海域占主导作用,O1分潮流次之。M2分潮流基本呈ENE—WSW向往复流特征,潮流最大流速介于20~29.6cm/s,最大流速分布满足5 m层以下逐渐减小的趋势;最大流速方向垂向变化不大;最大流速发生时刻随水深增加而提前。O1分潮流为NE—SW向的旋转流动,旋转方向为逆时针,在10 m水深以下,旋转率随水深增加而增大;潮流最大流速介于3.6~8.2 cm/s,最大流速垂向分布在靠近海岸的W1和W4站符合随水深增加而减小,而在靠近外海的W2和W3站则表现为5 m层以下逐渐减小的特征;最大流速发生时刻在W1—W3站表现为中层最早,表层次之,底层最迟;而W4站则表现为底层最早,中层次之,表层最迟。余流特征研究结果显示:夏秋季风转换期秦皇岛海域的余流较弱,流速介于0.3~2.5 cm/s之间。余流在表层和中层存在分叉现象,发生分叉的位置在秦皇岛海域中部的W1站和W3站附近,大约为39°40′N,而在底层表现为一致的偏北向流动。离岸较近的W1和W4站的余流在中层以下随水深增加向右偏转,具有Ekman螺旋结构特征。与辽东湾东侧海域的海流特征比较结果表明:秦皇岛海域的潮流从表至底均约为辽东湾东侧潮流量值的1/2。秋季辽东湾底层存在一顺时针旋转的弱环流系统,余流量值不超过5 cm/s,仅为辽东湾潮流量值的1/10。海洋对风的响应研究结果表明:秦皇岛海域中上层的余流在过程一中主要表现为对局地风场产生受迫响应的特征,而在中下层时受渤海中部流系的影响更大。秦皇岛海域的余流在过程二中则受东北风驱动的渤海中部顺时针环流的影响而表现为逆风的东北向流。水位在风速增加缓慢的情况下,对垂直海岸风呈受迫响应,而在迅速增强且持续时间较长的风场作用下,受风驱Ekman平流效应的影响而发生水位的增减。过程一中西南平行海岸风引起的离岸Ekman效应和离岸风的共同影响是导致底层温度下降的根本原因。过程二中东北平行海岸风增强驱动的向岸Ekman效应,使得渤海中部整层冷水的向岸补充,从而导致底层温度的显著下降。SST很好地指示了9月23日—24日东北风持续作用1 d后,秦皇岛海域海面出现的显著降温现象,主要表现为在SST图上出现了一由东北方向伸入观测点附近海域的冷水舌。风对海洋的能量输入研究表明:相较于潮流来说,秦皇岛海域的风场提供了海洋内部混合所需的主要能量。海面风场在过程一中通过10~16 h的近半日周期流动和4 d的亚潮频流动向海洋内部输入能量,而在过程二中主要通过近惯性运动向海洋内部输入能量。无论是在哪个过程中,海面风场都通过宽频段的流动从海表向下对海洋内部输入能量。惯性运动的能量主要来源于海面风场,且秦皇岛海域海面风场对惯性运动的能量输入存在一定的滞后效应,一般在大风过后的6~12 h内达到最大。海浪主要受风场控制,风速增长越快,海浪能量越大。
[Abstract]:Qinhuangdao sea area is the key sea area connecting Bohai and Bohai Bay, the main Bay of Liaodong Bay and Bohai Bay. It is an important channel for the exchange of material and energy in the Liaodong Bay and central Bohai and the Bohai Bay. The change and mechanism of the hydrodynamic process in the sea area are understood, the long-term transport and exchange of material and energy, the diffusion and separation of pollutants are also known. It is of great significance to study the self purification capacity of the sea area and the restoration of the ecological environment in the sea area. Based on the data obtained from the 4 sets of seabed base observation system in the Qinhuangdao sea area in September 2013, the continuous observation data of the water level and the bottom temperature, combined with the data of the simultaneous numerical wind field and the high resolution temperature field of the sea surface (SST), etc. The classical harmonic analysis method is used to analyze the tidal current and residual current characteristics of Qinhuangdao sea area in summer and autumn monsoon, and by comparing with the results from the east side of Liaodong Bay, the whole tidal current distribution and circulation pattern in Liaodong Bay are studied. On this basis, the response of the hydrodynamic factors in the Qinhuangdao sea area to the local wind field is explored. Finally, using the wavelet analysis method, the energy input and energy transfer mode of the residual current and wave in the wind field are studied from the angle of energy. The results of the flow characteristics study show that the tidal current in the Qinhuangdao sea area belongs to the regular half day tidal current, the W1 W4 station is in the shallow water flow area, and the shallow water tide is marked by the.M2 tidal current in the Qinhuangdao sea area. The dominant role is that the.M2 sub flow of O1 sub flow is basically ENE WSW, the maximum flow velocity is in the 20~29.6cm/s, the maximum flow velocity distribution satisfies the trend of gradually decreasing below 5 m layer, and the vertical direction of the maximum flow velocity varies little, and the maximum velocity occurs with the increase of the depth of water, and the.O1 sub flow is the rotational flow of NE SW direction ahead of time with the depth of the flow. The rotation direction is counter clockwise. Under 10 m water depth, the rotation rate increases with the depth of water; the maximum flow velocity of the flow is between 3.6~8.2 cm/s, the vertical distribution of the maximum flow velocity in the W1 and W4 stations near the coast decreases with the increase of the depth of water, while the W2 and W3 stations near the sea are gradually decreasing below the 5 m layer; the maximum flow rate occurs when the flow rate occurs. At the W1 - W3 station, the middle layer is the earliest, the surface layer is the latest, and the W4 station is the earliest, the middle layer, and the surface is the late surface. The residual current in the summer monsoon transition period shows that the residual current in the Qinhuangdao sea area is weak and the flow velocity is between 0.3~2.5 cm/s. Near the W1 station and W3 station in the middle of the Qinhuangdao sea area, it is about 39 degree 40 'N, while the bottom layer shows a consistent northward flow. The residual current of the nearer W1 and W4 stations along the middle layer increases to the right deviation with the depth of the water, and has the characteristics of the Ekman spiral structure. The comparison with the characteristics of the sea current in the eastern Liaodong Bay shows that the Qinhuangdao sea area The tidal flow from the table to the bottom is about the east side of the east side of the Liaodong Bay in the 1/2. fall, a clockwise rotating weak circulation system at the bottom of the Liaodong Bay. The residual flow value is not more than 5 cm/s. The result of the study on the response of the 1/10. ocean to the wind in the Liaodong Bay shows that the residual current in the middle upper layer of the Qinhuangdao sea area is mainly reflected in the process one. The wind field has the characteristics of forced response, while the middle and lower strata are more affected by the central Bohai flow system. The residual current in the Qinhuangdao sea area is affected by the clockwise circulation of central Bohai in the middle part of the northeast wind, which is the Northeast flow of the counter wind. The water level is forced to respond to the vertical coastal wind under the slow increase of wind speed. The water level increases and decreases under the effect of wind drive Ekman advection effect under the effect of rapidly increasing and longer duration wind field. The common influence of offshore Ekman effect and offshore wind caused by the southwest parallel coastal wind in the first process is the fundamental cause of the lower temperature decline. The bank Ekman effect, supplemented by the whole layer of cold water in the middle of Bohai, leads to a significant decrease in the bottom temperature of.SST, which is a good indication of the significant cooling of the sea surface in the Qinhuangdao sea area after the northeastern wind sustained action of 1 D from September 23rd to 24, which is mainly manifested in a northeastern extension of the sea area near the observation point on the SST map. The study on the energy input of the wind to the ocean shows that the wind field in the Qinhuangdao sea area provides the main energy needed for the internal mixing of the ocean compared to the tidal current. The sea wind field enters the ocean through the near half day periodic flow of 10~16 h and the 4 d tidal current flow in the process one, and in the second of the process the main passage is near. The energy of the inertial motion is inputted into the ocean. In any process, the wind field of the sea is inputted from the sea surface to the ocean through the flow of the wide frequency section. The energy of the inertial motion is mainly derived from the sea wind field, and the energy input of the sea surface wind field in the Qinhuangdao sea area has a certain lag effect on the energy input of the inertial motion. The 6~12 h reached the maximum after the wind. The waves were mainly controlled by the wind field. The faster the wind speed grew, the greater the wave energy.
【学位授予单位】：上海海洋大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P732;P731.2

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