Estimates of Reynolds stress in a highly energetic shelf sea     

Alejandro Jose Souza  Michael John Howarth 《Ocean Dynamics》2005,55(5-6):490-498

In recent years the use of Acoustic Doppler Current Profilers (ADCPs) to estimate Reynolds stresses, using the so-called variance method, has become popular; and although there was great effort in studying the uncertainties on this technique, there were no reports in the main literature of its validity using independent measurements. This work reports on the comparison of ADCP and Acoustic Current Velocimeter (ADV) estimates of Reynolds stresses. The comparison of the ADCP and ADV is encouraging during periods when no strong waves were present with both the explained variance of 0.8 and the slope of the regression being 0.97. Nevertheless, when strong waves are present the method breaks down and the comparison between ADCP and ADV is very poor with R² =0.04.  相似文献   

Measurements and three-dimensional simulations of flow in a shallow reservoir subject to small-scale wind field inhomogeneities induced by sheltering     

Sebastian Rubbert  Jürgen Köngeter 《Aquatic Sciences - Research Across Boundaries》2005,67(1):104-121

  相似文献   

Measurements of Reynolds stress in a wind-driven lagoonal estuary     

Anthony C. Whipple  Richard A. Luettich Jr.  Harvey E. Seim 《Ocean Dynamics》2006,56(3-4):169-185

Acoustic Doppler current profilers (ADCPs) have been used to measure Reynolds stresses in tidally dominated environments where wave action was minimal. In this paper, we examine observations from a microtidal estuary where the effects of wind stress and surface waves dominate the velocity variance. Reynolds stress measurements in this setting require a technique for addressing surface gravity wave contamination. We present here a method of reducing the effect of wave motion on Reynolds stresses by subtracting coincident observations along the axis of the ADCP beam. Linear wave theory is used to account for the attenuation of wave orbital velocities with depth. Using this method, Reynolds stress values are brought in line with those predicted by drag laws at the surface and bottom. The apparent Reynolds stress that is removed by the along-axis subtraction is shown to be largely due to the interaction of a slight tilt (1°) in the ADCP and the wave orbital velocity. During periods of stronger wind and waves, there is evidence of enhanced near-surface turbulence and momentum flux, presumably due to breaking waves. During these events, our calculated Reynolds stress magnitudes still appear reasonable, although the directions are suspect. We develop a diagnostic technique that clearly demarcates this region when it occurs. Coincident density profile measurements are used with the ADCP data to compute gradient Richardson numbers throughout the water column. Enhanced Reynolds stresses appear to correspond to Richardson numbers less than one. Responsible editor: Alejandro Souza  相似文献   

ADCP声波流速流向剖面仪在海洋环境监测与评价中的应用   总被引：4，自引：0，他引：4  

胡平  李文杰 《物探与化探》2004,28(4):341-344,348

在简述ADCP声波流速流向剖面仪基本原理的基础上，结合几个典型的环境监测工程实例，简单地介绍了该技术在香港特别行政区海洋环境质量监测、海洋工程环境评价等方面的应用成果。工程应用的实际结果表明，采用ADCP技术能够获得良好的环境监测效果，阐明了这一技术在环境质量监测应用方面的重要性和有效性。  相似文献   

Variability of Currents off the Northern Coast of New Guinea     

Yoshifumi Kuroda 《Journal of Oceanography》2000,56(1):103-116

The variability of the New Guinea Coastal Current (NGCC) and New Guinea Coastal Undercurrent (NGCUC) were examined from one year time series of current data from ADCP moorings at 2°S, 142°E and 2.5°S, 142°E. Change in the hydrographic structure induced by monsoonal wind forcing was also examined from hydrographic data along the 142°E covering consecutively two winter seasons and two summer seasons. The westward NGCUC was observed to persist year around. The annual mean depth of the current core was 220 m, the mean speed of the zonal component was 54 cm/s with a standard deviation of 15 cm/s at the 2.5°S site. Velocity fluctuations at 20–30 day period were observed year around. Seasonal reversal of the surface intensified NGCC was clearly observed. In the boreal summer characterized by the southeasterly monsoon, westward currents of over 60 cm/s were dominant in the surface layer. The warm, low-salinity layer thickened at this time and sloped down toward the New Guinea coast from the equator. This surface water accumulation may be caused by onshore Ekman drift at the New Guinea coast, combined with weak Ekman upwelling at the equator. In the boreal winter, an eastward surface current developed to 100 cm/s extending down to 100 m depth in response to the northwesterly monsoonal winds. Coastal upwelling was indicated in this season and the surface water accumulated at the equator due to Ekman convergence. Shipboard ADCP data indicated that the NGCUC intensified in boreal summer as the width and depth of the NGCUC increased.  相似文献   

ADCP application for long-term monitoring of coastal water   总被引：3，自引：1，他引：2  

YOSHIOKA Hiroshi  TAKAYAMA Tomotsuk  SERIZAWA Shigeatsu 《海洋学报(英文版)》2005,24(1):95-100

Three kind of application of ADCP is reported for long-term monitoring in coastal sea. (1)The routine monitoring of water qualities. The water quality and ADCP echo data (600 kHz) observed in the long-term are analgzed at MT (Marine Tower) Station of Kansai International Airport in the Osaka Bay, Japan. The correlation between the turbidity and echo intensity in the surface layer is not good because air bubbles generated by breaking wave are not detected by the turbidity meter, but detected well by ADCP. When estimating the turbidity consists ofplankrton population from echo intensity, the effect of bubbles have to be eliminated. (2) Monitoring stirring up of bottom sediment. The special observation was carried out by using following two ADCP in the Osaka Bay, One ADCP was installed upward on the sea. The other ADCP was hanged downward at the gate type stand about 3 m above from the bottom. At the spring tide, high echo intensities indicating the stirring up of bottom sediment were observed. (3) The monitoring for the boundary condition of water mixing at an estuary. In summer season, the ADCP was set at the mouth of Tanabe Bay in Wakayama Prefecture, Japan. During the observation, water temperature near the bottom showed remarkable falls with interval of about 5～7d. When the bottom temperature fell, the inflow current with low echo intensity water appears at the bottom layer in the ADCP record. It is concluded that when occasional weak northeast wind makes weak coastal upwelling at the mouth of the bay, the combination ofupwelling with internal tidal flow causes remarkable water exchange and dispels the red tide.  相似文献   

Conversion of Pressure to Depth for Moored Instruments Using a Reference Bottom Mounted Pressure Sensor     

Junde Li  Weifang Jin  Guanghong Liao  Beifeng Zhou 《大气与海洋》2015,53(4):377-382

A new method is proposed to convert pressure measured by an instrument to water depth using an additional available bottom-moored pressure sensor. A perturbation analysis is used in this analysis, which leads to a simple formula for calculating water depth (defined as one from the mean sea surface to the instrument) from the pressure data. In field experiments, this method is easier to apply than existing methods. Based on the theoretical derivation, the error associated with the method comes from two sources when the instrument depth is known at the beginning of the measurement: temporal variation of deep water density at depths deeper than the instrument and variation in the gravitational acceleration with instrument displacement. These two sources contribute up to 4% of the error relative to the vertical displacement of the instrument, assuming the pressure sensor is accurate. With the vertical displacement of the instrument being on the order of 10?m, the absolute error is on the order of 0.4?m, which is expected and acceptable in oceanic measurements. The method is applied to data from a field experiment that took place along the Myanmar coast in December 2012.  相似文献   

基于走航ADCP资料的厦门内湾东西口门海域潮流与潮致余流特征分析   总被引：1，自引：0，他引：1  

沈俊强  ;潘伟然  ;张国荣  ;骆智斌  ;林毅辉 《台湾海峡》2014,(3):395-403

应用厦门内湾东西3个口门断面（五通—下店、嵩屿—鼓浪屿、鼓浪屿—轮渡）一个潮周日走航ADCP资料的空间插值潮、流调和分离结果,分析占主导的M2分潮流与余流沿断面的空间分布特征.分析结果表明受地形约束的3个断面M2分潮流均以往复流为主,断面深槽为主流通道,M2分潮最大可能流速均沿主流深槽向左右岸递减,三断面中以鼓浪屿—轮渡断面最为强劲,平均值为46 cm/s,五通—下店断面次之为43 cm/s,嵩屿—鼓浪屿断面最弱,仅为33 cm/s.该半日潮波进入厦门内湾首先在鼓浪屿—轮渡断面达到最大值,出现时间在月中天后2.1 h,其次为五通—下店断面2.7 h,最后为嵩屿—鼓浪屿断面3.3 h.再者地形变化剧烈的嵩屿—鼓浪屿断面M2分潮非线性运动较强,浅水分潮的幅度增大.潮波的非线性效应又衍生了非周期性的潮致余流,该余流在厦门内湾东西口门有较为稳定的存在,且表现为近岸区流幅大,潮流通道内小,嵩屿—鼓浪屿与鼓浪屿—轮渡断面均值为9 cm/s,五通—下店断面均值为5 cm/s,同时各个断面余流均存在使内湾海水正常更替,沿断面法向一分为二,一进一出的态势.基于本次观测结果计算出一潮周日厦门内湾东西口门余流通量为76.156×10^6m3,净潮通量为69.591×10^6m3,相对偏差小于8.6%.  相似文献   

船载ADCP资料处理          下载免费PDF全文

吴云帆  吴中鼎  李占桥 《海洋测绘》2014,34(6):36-39,42

通过对大量走航ADCP观测资料的分析,提出一整套的ADCP资料质量控制和预处理方法,并对提出的ADCP"基准流速控制"的处理方法与传统的"选取参考层法"进行了比较,证明此方法不但可有效提高ADCP资料的处理精度,并可提高资料的处理效率,减少人为的干预因素。  相似文献   

Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea     

《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(8):875-884

An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site of the ANTARES neutrino telescope near Toulon, France, thus providing a unique opportunity to compare high-resolution acoustic and optical observations between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward vertical currents of magnitudes up to 0.03 m s⁻¹ in late winter and early spring 2006. In the same period, observations were made of enhanced levels of acoustic reflection, interpreted as suspended particles including zooplankton, by a factor of about 10 and of horizontal currents reaching 0.35 m s⁻¹. These observations coincided with high light levels detected by the telescope, interpreted as increased bioluminescence. During winter 2006 deep dense-water formation occurred in the Ligurian subbasin, thus providing a possible explanation for these observations. However, the 10-20 days quasi-periodic episodes of high levels of acoustic reflection, light and large vertical currents continuing into the summer are not direct evidence of this process. It is hypothesized that the main process allowing for suspended material to be moved vertically later in the year is local advection, linked with topographic boundary current instabilities along the rim of the ‘Northern Current’.  相似文献