HF Radar detected water wave velocity over the Northern Jiangsu Shoal

应用雷达波dOPPlEr正频移与负频移信号联解波速和径向流速方法,在2011年7月苏北浅滩高频地波雷达观测试验中实现潮间浅滩海面波浪传播速度的观测.基于频移与波速两级数据质量控制后统计的苏北浅滩平均波速平面分布图,可分辨出与潮间浅滩、水下岸坡和潮汐水道等浅滩地貌单元相关的波速分区格局.同步检验表明:雷达观测波速与现场观测水深的关系统计意义上遵循微幅波理论,径向流速较大条件下的波速观测质量较好,复杂地形所致双向波速不等现象导致波速观测质量降低,高频地波雷达是潮间浅滩动态遥感监测的潜在工具.High-frequency(HF) radar systems can provide wave velocity and radial current by identifying and tracking frequency shifts in the peaks of the Doppler spectra of the ocean backscatter corresponding to the advection of the Bragg wave.Data used in this study was collected by HF radar experiment for the Northern Jiangsu Shoal in July 2011.A distribution of monthly average wave velocity was generated with data that is quality controlled particularly.The intertidal flat, offshore shoal and tidal channel, associated with low speed area, high speed area and high speed belt respectively, could be distinguished by the HF radar mapped wave velocity distribution.After compared with datasets of field measurement and calculate results, it is revealed that(1) the relationship between water depth and monthly average wave velocity fits the theory of Airy Wave,(2) large radial currents may rise measurement accuracy of wave velocity, and 3) mismatch of approaching and leaving wave velocity related to complex topography may reduce measurement accuracy.海洋公益性行业科研专项经费(201005012;201005006); 国家自然科学基金(40876031); 国家高技术研究发展计划(2012AA091701); 江苏省科技计划项目基础研究计划(SBK201150144)资

Spatial and temporal variations in salt-marsh vegetation in Wanggang area,Jiangsu coast,based upon TM imagery analysis

通过对2002~2003年度3个时相的Landsat TM图像进行监督分类处理,研究了盐沼植被的分布和变化。结果表明,目前盐蒿和大米草(Spartina anglica)占据的面积很小,年际变化不大,由于滩涂围垦的影响其面积还在进一步缩小。互花米草(Spartina alterniflora)成为优势种,占据了大部分的盐沼面积,向海蔓延显著,扩张的趋势还在持续,其覆盖面积的年增长速率可达18%。Wanggang area is a typical region of tidal flats.In the 1960s and 1980s,Spartina anglica and Spartina alterniflora were artificially introduced, respectively,to this area.Appearance of Spartina marshes changed the sedimentary environment of the tidal flats.Using Landsat-TM data,the vegetation change and consequent modifications to the geomorphology of the tidal flat system were analyzed.Firstly,field observation and sampling were undertaken to investigate the biological feature of the three main salt-marsh species: Suaeda salsa,Spartina anglica and Spartina alterniflora.Observations in the four different seasons show that summer represents a period of rapid growth.In autumn the plants have the highest biomass.Thus,3 Landsat-TM images from 29 July 2002,24 July 2003 and 28 October 2003 were used to map the vegetation distribution and annual change.Using the in situ data,spectral features obtained show that Bands 3,4 and 5,in combination with field observations,contain sufficient information to distinguish the 3 different kinds of plants.Supervised classification using Bands 3,4 and 5 with in situ calibration was performed to derive the distribution pattern of the vegetation in Wanggang areas.The result shows that:(1) Spartina alterniflora is expanding towards the sea,with a rate of several hundred meters per year;(2) in the upper part of the inter-tidal zone,Suaeda salsa and Spartina anglica are distributed near the sea dyke,but reclamation has reduced the area of these two kinds of marshes;and(3) from 2002 to 2003,the area covered with Spartina alterniflora increased by 18%.国家自然科学基金重点项目(40231010);; 教育部博士点基金项目(20020284007

Characteristics of the large-scale sandwaves,tidal flow structure and bedload transport over the Taiwan Bank in southern China

对2006年8月所获台湾浅滩的底质、水深、多层位流速、流向以及CTD观测数据进行了分析,探讨了台湾浅滩大型沙波区水流的时空分布特征、沉积物输运过程及影响因素,结果表明,台湾浅滩动力作用较强,底质为粗砂,其上发育的沙波波长为325~822 m,波高为14.4~20.3 m,较接近由前人总结的沙波波高、波长的关系式计算出的波高和波长。沙波波峰、波谷、迎水面和背水面流速以12.5 h为周期沿顺时针方向旋转;底部最大流速出现在半日潮周期的同一时段,对应的方向均为偏南方向,且沙波迎水面的流速大于背水面的。在两个半日潮过程中研究区域的沉积物输入量大于输出量,处于淤积状态。在潮流作用下沉积物输运量较少,沙波脊线移动较小,而台湾浅滩有较大规模的沙波运动,故认为改造沙波的主要作用力应该是风暴流。在观测的断面中涨潮推移质输运量大于落潮的,且第一个半日潮涨落潮的输运能力均较第二个半日潮的大,这可能与潮流的流速-时间不对称特征及潮能变化形式有关。On the basis of the measurement of current velocity within the water column,water depth and physical properties of seawater over the Taiwan Bank in August 2006,the spatial and temporal characteristics of current velocities over large-scale sandwaves,together with the process of sediment transport,are analyzed.The results show that the sandwaves,14.4~20.3 m in height and 325.4~821.8 m in length,are formed under the conditions of strong current that is acting upon the bed consisting of coarse-grained sediments,with a height-length relationship similar to those identified elsewhere in previous studies.Currents at the sandwave crest,trough,stoss-side and lee-side turn in a clockwise manner with a period of 12.5 h.In the bottom layer of the water column,the largest velocity occurred at the same phase of each semidiurnal cycle,which was directed to the south;furthermore,the velocities on the stoss-side are larger than on the lee-side.During the two semidiurnal tidal cycles,the amount of sediment imported into the study area was larger than output,indicating that accretion was taking place.The sediment transported by tidal current was relatively weak,which could cause only slow migration of sandwaves.However,according to satellite observations,the sandwave migration can be high over the Taiwan Bank.This phenomenon may be caused by the strong currents associated with storm events.At the cross-section studied,sediment transport was more intensive during the flood than during the ebb,and the net fluxes varied for different semidiurnal tidal cycles,indicating the effects of the time-velocity asymmetry and the tide phase.国家自然科学基金资助项目(40476023

山东月湖的沉积物分布特征及搬运趋势

1998年 11～ 12月和 1999年 8～ 9月各一个月对月湖进行的野外工作 ,共取得表层沉积物样品 131个 ,应用激光粒度仪并结合传统的筛分法对这些样品进行粒度分析 ,进行矩法计算获得粒度参数。采用Gao命名方法 ,将沉积物划分出 5种主要类型。利用Gao -Collins粒径趋势分析模型 ,计算该区沉积物粒径趋势所显示的沉积物净搬运方向 ,结果表明 ,沉积物从四周向湖中心搬运 ,同时显示湾顶的西部和北部、涨潮三角洲以及湖心等地貌单元是沉积的优势区域

A Coastal Dune Overwash Record of Typhoon Storm Events from Southeastern Hainan Island

通过海南岛东南部海岸详细的古风暴学考察,在尖岭海岸发现了含有风暴冲越沉积物的海岸沙丘剖面,分别命名为JL-1和JL-2剖面,试图从海岸沙丘沉积记; 录中提取历史上的风暴事件信息。沉积物粒度、磁化率等参数的指标分析表明,这两个剖面含有典型的风暴冲越沉积物,利用放射性核素AMS~(14)C测年、; OSL测年分析,并结合历史文献记载,确定这些风暴沉积层是多次台风作用的产物,其形成机制与风暴浪越过海岸沙丘的堆积有关,风暴流越过沙丘顶部后不能回; 流,导致风暴流携带的沉积物迅速沉积。此外,依据Stockdon经验公式计算结果,该地点沉积记录所代表的最大风暴事件相当于100到200年一遇的重; 现期。研究表明,该处海岸沙丘冲越沉积含有南海台风强度与重现期的重要信息。In the present study, coastal dune deposits are analyzed to derive the; information on historical storm events. Paleotempestology investigations; were carried out for the southeastern part of Hainan Island. The storm; deposits identified are interbedded within the aeolian coastal dune; profiles on the Jianling coast. They are characterized by coarse-grained; overwash deposits during the extreme storm events, as revealed on the; basis of detailed stratigraphic division, grain size and magnetic; susceptibility analyses. The age of the storms events was determined; using the ~(14)C and OSL dating methods, in combination with historical; documents. When a storm surge hits the coast, the coastal dune may be; overtopped or breached, and a low-lying dune associated with a large,; flat terrain at the backshore is suitable for trapping the storm; sediment to form a thick-bedded, sandy washover deposit. The Stockdon; empirical equation was used to calculate the overwash height, indicating; that the storm record at the Jianling site represents the product formed; by several storms, with their return periods being 100 to 200 years. The; result obtained implies that the coastal dune here contain important; information on the intensity and frequency of occurrence of the South; China Sea typhoons.国家自然科学基金重点项