【作者】 朱大勇；

【导师】 李立； 李炎；

【作者基本信息】 厦门大学 ， 物理海洋学， 2008， 博士

【副题名】以台湾海峡为例

【摘要】 高频地波雷达利用垂直极化的高频电磁波沿高导海水表面传播时能量衰减较小的特性,对海洋环境状态（如风、浪、流等海洋动力学参数）、海上低速移动目标等实现超视距监测和定位。与传统仪器比较,其具有观测距离远、覆盖面积大、反演要素多、可全天候工作等特点,与卫星遥感相比则具有造价低、空间分辨率与采样频率高等特点。随着技术的进步,地波雷达在近海观测系统中逐步发挥着重要作用,并成为数据的重要补充。本研究依托于863计划福建示范区项目,应用设备为武汉大学设计制造的高频地波雷达OSMAR系统。利用2005年6,7月安装调试初期的观测表明,该雷达观测采样的周日变化明显,采样覆盖率50%的观测范围可达到125km。雷达径向流的潮流分布与传播特征的空间特征与以往研究相似,表明该雷达观测海流结果的合理性,不同时段观测结果的一致性也证明了该雷达的稳定性。利用福建示范区内的浮标ADP以及908座底式潜标ADCP的海上观测,以同步序列的距离均方差为比测误差评价标准,对福建示范区OSMAR2003海流的观测误差进行了验证,东山、龙海两雷达站径向流的比测误差在7.6-12.5cm/s之间,方位角误差在10°以内,合成矢量流流速以及u,v分量在8.6-13.0cm/s之间。利用台湾浅滩沙波区域的走航ADCP的海流观测,并与基于雷达观测预报的潮流结果的比测误差为10.4cm/s,雷达观测的结果代表了区域的平均结果。对以往雷达反演海流的比测验证进行总结并发现,雷达海流的观测误差在7-20cm/s之间,误差主要来源不仅来自仪器自身的观测误差,同时也与雷达和比测仪器观测目标之间的差异有关。就海流观测,OSMAR2003地波雷达的观测能力达到了国外同类产品的水平,且雷达在运行期间的测度稳定。故此,本文利用高频地波雷达的海流观测,开展台湾海峡海洋学研究。利用雷达的冬季观测,揭示了东山-龙海附近海域的表层潮流的精细结构特征,潮流的主要特征与以往的认识基本一致,潮流椭圆旋转率零线比以往的研究更偏北,在浮头湾附近向东南偏东方向延伸。S₂、O₁分潮流的椭圆主轴指向、旋转率的分布特征与M₂分潮的分布特征相似,潮流振幅大致为M₂分潮的1/3和1/10。台湾海峡由南向北传的谐振潮波与由北向南来传播潮波的共同作用,K₁分潮在澎湖列岛西侧海域出现了逆时针旋转的圆流点。2006全年的观测表明,台湾海峡西侧表层流场的的变化主要为冬夏两个阶段,11-5月为冬半年,6-10月为夏半年;由冬向夏的转换较为缓慢,而由夏至冬的转换迅速,主要受制于季风。顺岸风速与顺岸流速的统计关系以及ADCP的海流剖面观测表明,台湾海峡西侧的平均10cm/s的北向背景流（backgroundcirculation）常年存在,春夏季流速为10-20cm/s,冬季小于5cm/s。表层因受季风控制而体现为漂流特征,上Ekman层以下为常年的北向背景流控制。进一步分析冬季表层海流的亚潮波动,发现其以顺岸分量为主。风、海流、福建沿岸水位的波动特征具有较强的相似性,主要波动周期分别为8天,4.6天,3.2天和2.3天。4.6天和3.2天波动周期的海流波动为远地风与局地风的混合作用,前者以远地风强迫为主,后者则以局地风为主。2.3天的波动周期,水位与余流的波动均不受局地风以及远地风驱动传播的影响。最后,以南海北部陆架区域对台风的近惯性振荡响应过程为基础,0519号台风“龙王”期间,台湾海峡流场对台风过程的响应得以体现,台湾海峡流场流向受风向控制发生显著改变,影响持续时间在4-5天左右。台风过境后,流场迅速恢复至潮流强迫,并且无自由振荡出现。本文以福建示范区地波雷达监测系统两年多的运行为基础,对高频地波雷达的多方面相关内容进行全面总结,验证了OSMAR2003的观测误差,并应用于观测区域的潮流、海流、亚潮波动、台风响应等内容的研究,为今后高频地波雷达的发展与应用以及在台湾海峡海洋学研究奠定了基础。更多还原

【Abstract】 Based on the mechanism that the vertically polarized electromagnetic wave of high frequency can diffract along a curved sea surface without significant energy diminishing,high frequency ground wave radar（HF radar） can monitor the information of the sea surface current,sea wave,wind and slow-moving objects. Compared with traditional marine instrumentations,it can measure longer distance, larger coverage area,much more factors and operating under all weather conditions. It has the advantages such as lower cost,higher spatial resolution and sampling frequency by comparision wiith marine satellite remote sensing.So,HF radar observations are important supplements to ocean research.This thesis is supported by the National 863 Plan Fujian Demonstration and the OSMAR2003 HF radar produced by Wuhan University.Significant diurnal variations of the samples observed by HF radar can be detected at the beginning of radar operation through June to July,2005,and that the coverage range reaches～125km at 50%sampling rate.The spatial pattern of tidal distribution and propagation characters for radial currents are generally consisted with previous investigation,which shows that the radar observational results are reasonable.And the stability of radar operational is also confimed.Using the measurements from buoy ADP and bottom_mounted ADCP,the observation error of the Fujian Demostration OSMAR2003 sea currents is testified. The distance root mean squre（RMS） of the current speed series is the defined validition standard.The RMSs of radial current speeds in Dongshan and Longhai site are 7.6-12.5cm/s and the error of the radial current bearing is less than 10 degree,and the vector current speeds and u,v components range between 8.6-13.0cm/s respectively.The RMS of the under-way ADCP’s currents in Taiwan Bank and tidal current forecasted by the radar observations is 10.4cm/s.The errors of most of HF radar currents are mainly 10-20cm/s,which possibly caused by instrument errors and observation target differences.The OSMAR2003 has the same level of measurement precision with those by the same type of radars used other countries.The longterm observation has also testified the stability of the OSMAR2003 radars.With the current observations by HF radar,some applications researches in Taiwan Strait ocean dynamical process have been conducted,as presented follows. Using winter-time observations,we obtain the fine features of surface tidal current in the Dongshan-Longhai coast area.The tidal current characters are consitent with previous results.And the tidal ellipse rotating zero line of the M₂ constitunent is located near to the Futou bay,which is much norther than that reported in previous result.The distribution pattern of the S₂ and O₁ constitunets are similar to the M₂,and the tidal current amplitudes are one-third and one-tenth of that for M₂,respectively. Impacted by both the southwardly resonance and the northwardly tidal wave,a counter-clockwise rotational zero current point of the K₁ constitunent appears in the west of the Penghu Island.The annual variations of the sea surface current in the west Taiwan Strait are investigatied by using the observations in 2006.The variaition of the surface current indicates two patterns:from Novermber to next May,it is winter-time pattern,with the left months being the summer-time pattern.The pattern transformation is much slowly from the winter to the summer with～2-3 months;whereas,it is much quick from summer to winter,with only 1 month.These variabilities are mainly caused by the seasonal monsoon.With the ADCPs’ profile observations,the relationship between the longshore wind and current details the northward background circulation exists all the year around from the surface to the bottom with averaged speed～10cm/s, and being 10～20cm/s in spring and summer and smaller than 5cm/s in winter.Forced by the seasonal monsoons,the surface current is obviously wind drift,and the currents under the Ekman layer are northward all the year.The original study of the sub-tidal fluctuations for the winter surface current in radar coverage area is explored,and the longshore component is the primary.The wind,sea current and sea level show similar variations with the significant periods of fluctuations being 8d,4.6d,3.2d and 2.3d.The 4.6d and 3.2d significant periods of current fluctuation are both affected by remote wind and local wind,with the former mainly effecting 4.6d and the latter affecting 3.2d.The sea level and current fluctuations of 2.3d significant period are not affected by the wind field metioned above.We also investigate the response of the near sea area to the typhoons’ passages. Based on one case of the ocean inertial oscillations in the northern shelf of the South China Sea,we analyses the response of the Taiwan Strait to the No.0519 typhoon Longwang with the OSMAR2003 observations.And we find that,the effecting duration of typhoon is about～4-5 days and the current response is expeditious,the current direction changes with the wind direction and,current fields return to strong tidal force condition rapidly without any inertial oscillation occurring.By using the two year observations of the HF radar system in the Fujian Demonstration,we comprehensively summarize many aspects of HF radar in this thesis;also validate the measurement error of the OSMAR2003 radar,and exploit many application researches on the tidal currents,sea currents,sub-tidal fluctuations and response process to typhoon passage in the observation area.We procees many basic works for developments and applications of HF radar and oceanography researches in the Taiwan Strait.更多还原