共查询到17条相似文献，搜索用时 93 毫秒
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作者采用浊度计和声学多普勒流速剖面仪(ADCP)在近海区域连续、定点观测的应用中,利用浊度与悬沙浓度之间良好的线性关系,对潮汐半月周期内的浊度和ADCP后向散射声强数据进行相关性分析,讨论了小、中、大潮期间利用ADCP后向散射声强反演悬沙浓度的可靠性,反演过程中综合考虑了声学近场非球面扩散和本底噪声的影响。结果表明,在实验海域中,小潮情况下,各水层内悬浮泥沙成分较为稳定,ADCP后向散射声强与浊度变化相关性较高,达到0.91;而在大潮情况下,ADCP后向散射声强与浊度变化的相关性降低,悬沙浓度及成分容易在海流的影响下发生变化。 相似文献
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传统的悬浮泥沙浓度测量方法存在着各种不足,而ADCP(声学多普勒流速剖面仪)具有观测悬浮泥沙浓度的潜能.文章目的在于利用BP神经网络强大的非线形处理能力和黑箱模型的优势探讨长江口区快速测量悬浮泥沙浓度的可能性.根据2006年7月在长江口区的20个站位使用RD300K型宽幅ADCP测量得到的实测资料,提取其回声强度信息,把回声强度、温度、盐度、流速作为输入层变量,利用BP算法反演悬浮泥沙浓度,结果表明此方法精度较高(平均相对误差为18.64%),说明利用4-4-1模式的BP人工神经网络算法拟合长江口区表层悬浮泥沙浓度是可行的,但拟合效果与流向无关,而是与采样现场的海况有很大关系.海况越好,拟合效果也越好.在拟合除表层以外其他水层时需要考虑声波传输过程中各水层物理性质的变化. 相似文献
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现场粒径分析仪与ADCP同步测量悬浮沉积物浓度的粒径修正方法 总被引：8，自引：2，他引：8
利用后散射强度(ABS)估计悬浮沉积物浓度原理，根据Rayleigh散射理论，给出了利用现场粒径分析仪与声学多普勒流速剖面仪(ADCP)同步测量悬浮沉积物浓度的粒径修正方法，并推导出了一种新的、用于对ABS进行粒径修正的等效粒径计算公式(9)。利用这一公式并结合LISST-100所测的粒径分布信息，可以对ADCP所测的ABS进行粒径修正，其修正方法见式(10)。结合利物浦湾和Anglesey周边海域的现场采样、测量及其分析结果，对上述粒径修正方法进行了验证。分析结果表明，采用上述公式进行粒径修正后，ADCP测量悬浮沉积物浓度的精度有较大程度的提高，线性拟合的相关系数从0．65-0．71提高到0．78-0．88。 相似文献
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ADCP对悬浮沉积物浓度的测量及其误差分析研究 总被引：6，自引：0，他引：6
为实时、连续地测量海水中悬浮沉积物，利用声学多普勒海流剖面仪(ADCP)，可以在测流的同时，测量海洋悬浮沉积物浓度。描述了利用后散射强度，估计悬浮沉积物浓度的原理。在现场测试中，利用采水器采集水样，通过水样分析并结合声信号的衰减特征对AI)CP的测量结果进行修正。作者还结合现场测试结果，对这一测量方法的精度进行了分析。现场实验表明，经公式校正后，ADCP测得的后散射强度与实测水样所获得的悬浮沉积物浓度之间有很好的相关性，相关系数达0．88，由此证明，此测量方法具有很好的实用价值和应用前景。 相似文献
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基于声学仪器与粒径分析仪研究东海浮游动物昼夜垂直迁移过程 总被引：1，自引：0，他引：1
浮游动物的昼夜迁移活动与其种群变动和摄食节律紧密联系,浮游动物昼夜移动的研究已经成为种群动力学研究的一个重要组成部分。2013年夏季在浙江东部近海,结合声学多普勒流速剖面仪(ADCP)和激光粒径分析仪(LISST-100)等仪器进行了一次定点周日连续观测。通过声学反演方法,得到后向散射强度剖面的时间变化,结合LISST-100得到的水体悬浮物粒径谱,研究了浮游动物垂直迁移及其习性。分析发现了可能是精致真刺水蚤的一次昼夜垂直迁移过程,其在夜间进入跃层附近进食,白天蛰伏于底层低温高盐的台湾暖流水中,垂向迁移速度达到了0.05 m/s。LISST-100观测还发现在夜间跃层边界处大粒径颗粒聚集和100～150 μm大小的颗粒物的减少,水体中不同粒径的悬浮颗粒物有明显的昼夜变化节律,推测水体中不同层次生物群落结构存在昼夜差异。 相似文献
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在金塘水道西口门2006年冬季和2007年夏季大、小潮期间应用美国RDI公司生产的300 kHz声学多普勒流速剖面仪(ADCP)进行25 h的走航式断面观测,同步采集水样过滤获得悬沙浓度.实测断面流速、流向表明:落潮时流向为东南向,涨潮时分两股,靠近北仑为西南向,靠近金塘岛为西北向;夏季大潮最大流速为260 cm/s,大于冬季大潮;观测期间断面悬沙浓度为0.4～1.5 g/L,冬季大于夏季约0.3～0.5 g/L;ADCP后向散射强度冬季大于夏季约5 dB.应用实测CTD数据进行声吸收系数校正,通过计算,断面后向散射强度分布趋势基本不变.后向散射强度与悬沙浓度成正比,与水深成正比,垂向分布与潮时有关,冬季小潮水深增大时,后向散射强度反而减小.回归ADCP后向散射强度与水样悬沙浓度之间半经验半理论统计关系,发现冬季不成线性关系,夏季成线性关系,且相关性较好,相关系数为0.7,说明夏季较高浓度下后向散射强度可以表示悬沙浓度的大小.夏季大、小潮期间高分辨率的悬沙浓度断面数据分析表明,反演后的悬沙浓度值与流速成正比;近岸悬沙浓度大于断面中部;涨急和落急时同一水深高低含沙量值错落分布,涨憩和落憩则分层明显;大潮悬沙浓度大于小潮流约0.05 g/L.断面两端点反演后的悬沙浓度与实测值比较,呈现半日潮含沙量双峰特征,夏季大潮反演后的悬沙浓度与实测值分布一致,实测值大于0.9 g/L时,两者量值相差大,小潮则拟合很好.因此,应用走航式ADCP测量高悬沙浓度是可行的,它可大大提高测量效率,为获取现场悬沙浓度提供了一种新方法. 相似文献
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《海洋与湖沼》编辑部 《海洋科学》2011,35(3):108-109
莱州湾口弱层结水体中沉积物再悬浮特征及其水平、沉降通量研究利用ADCP回声强度反演得到了高分辨率的悬浮物时空分布,在详细分析潮流、波浪以及密度层结变化的基础上,指出以上诸因素是影响沉积物再悬浮的主要机制。潮流和波浪联合作用于底床使沉积物起动进入水体,而层结强度与位置的变化则是起动的沉积物能否有效再悬浮 相似文献
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《Coastal Engineering》2005,52(2):103-118
The ability of a 1.2-MHz Acoustic Doppler Current Profiler (ADCP) to measure suspended sediment concentration (SSC) and particle size variation in a mud-dominated environment has been investigated. Experiments were conducted in the Bay of Banten, Indonesia, where clays and silts in the range of 3–55 μm are prevalent. The ADCP backscatter depends both on SSC and on the size of the scatterers. Over the time span of several separate deployments, which lasted 20 days at most, SSC was found to be proportional to the acoustically normative grain size squared. Using this relation, the ADCP could be calibrated to yield depth profiles of SSC. The obtained calibrations, however, were spatially and seasonally dependent. Differences between the calibrations could not be completely ascribed to variation in grain size distributions, due to the largely unknown influences of aggregates and organic scatterers. The ADCP backscatter measurements provided insight into diurnal events of erosion and subsequent deposition. An increase or decrease of SSC generally coincided with a raise or decline of the average grain size in the sediment suspension (respectively). 相似文献
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Frédéric Jourdin Caroline Tessier Pierre Le Hir Romaric Verney Michel Lunven Sophie Loyer André Lusven Jean-François Filipot Jérémy Lepesqueur 《Geo-Marine Letters》2014,34(4):381-397
A pair of self-contained acoustic Doppler current profilers (SC-ADCPs) operating with different frequencies were moored on a muddy sea bottom at about 20 m depth in the Bay of Vilaine off the French Atlantic coast. With their acoustic beams oriented upwards, the SC-ADCPs ensonified most of the water column. The results of several months of in situ recorded echo intensity data spanning 2 years (2003 to 2004) from the dual-frequency ADCPs are presented in this paper. The aim was to estimate suspended particle mass concentration and mean size. A concentration index CI is proposed for the estimation of particle concentration. Based on theory the CI—unlike the volume backscatter strength—does not depend on particle size. Compared with in situ optical data, the CI shows reasonable precision but not increased with respect to that of the highest-frequency backscatter strength. Concerning the mean particle size, despite a lack of quantitative validation with optical particle-size measurements, the method yielded a qualitative discrimination of mineral (small) and organic (large) particles. This supports the potential of dual-frequency ADCPs to quantitatively determine particle size. A cross-calibration of the transducers of each ADCP shows that a specific component of the precision of the backscatter strength measured by ADCP depends on the acoustic frequency, the cell thickness and the ensemble integration time. Based on these results, the use of two ADCPs operating with distinctly different frequencies (two octaves apart) or a single dual-frequency ADCP is recommended. 相似文献
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ADCP measurements of suspended sediment flux at the entrance to Jiaozhou Bay, western Yellow Sea 总被引：1，自引：1，他引：0
The purpose of the present contribution is to explore the technique to use Acoustic Doppler Current Pro- filers （ADCPs） for suspended sediment flux measurements, which may be applied to coastal embayment environments such as estuaries and tidal inlets for sediment exchange and budget studies. Based on tidal cycle measurements from the entrance of ]iaozhou Bay, Shandong Peninsula, eastern China, statistical rela- tionships between the suspended sediment concentration （SSC） and ADCP echo intensity output are estab- lished. Echo intensity data obtained during an ADCP survey along two cross-sections during a spring tidal phase were transformed into SSC data. The ADCP current velocity and SSC data were then used to calculate the flux of fine-grained sediment. The results show that net sediment transport at the entrance is directed towards the open sea, with an order of magnitude of 103 t per spring tidal cycle; hence, although Jiaozhou Bay is a low SSC environment, the tidally induced suspended sediment transport can be intense. 相似文献
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A.J.F. Hoitink 《Marine Geology》2004,208(1):13-31
The Bay of Banten, West Java, Indonesia represents a shallow coastal embayment harboring coral reefs subject to extremely turbid conditions. The sedimentary regime and flow structure of two contrasting coral reef islands in the embayment were investigated to identify the mechanisms responsible for mean and peak levels of suspended sediment concentration (SSC) around the reefs. Arrays of in situ calibrated optical backscatter (OBS) sensors were deployed across the reef slopes. Far field conditions were simultaneously monitored using an acoustic Doppler current profiler (ADCP) and a conductivity temperature and depth (CTD) probe, equipped with an OBS sensor. In addition, hydrographic surveys were conducted using the ADCP attached to a small fishing boat, navigating transects perpendicular to the reef islands. The direct influence of river plumes was found to be insignificant. Waves act only in the uppermost few meters of the reef slopes, where coral growth is most abundant and little sediment is available for resuspension. Tidal currents are the primary cause of high turbidity, which was inferred from peaks in the diurnal and semidiurnal frequency bands of SSC spectra, and the large depths where the turbidity variation sometimes initiates. The entrained sediment disperses upward across the reef slopes, which is likely due to a secondary current associated with bending of the flow along the curved, hydraulically rough reef slopes, in weakly stratified ambient waters. Changes in sediment availability, variable critical shear stresses for erosion and deposition, and the formation and evanescence of island wakes may explain the high variability of SSC at the reef slopes. 相似文献
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The grain-size of suspended particulate matter (SPM) in the Huanghe Estuary and its adjacent sea area was investigated with an in situ laser particle size analyzer (LISST-100) in November 2006.The spatial distribution of the grain-size parameters was very complicated.The results show that (1) the mean particle size of SPM ranged from 3.00Φ to 6.41Φ,with an average value of 4.66Φ;(2) the frequency distribution patterns of the SPM grain-size showed three different types,which were mono-mode,dual-mode and tri-... 相似文献