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1.
An Nd:YAG-based airborne lidar system has been used to measure the optical properties of littoral waters off the northwest Scottish coast. The small-scale structure of subsurface scattering layers was also investigated. Methods of solving the Lidar Sensing Equation in the single scattering approximation are described and the values of the derived extinction indices presented. The extinction index averaged over a series of five flights to the northeast of the Gulf Stream was ε= 0.224 m -1 with a standard deviation of 0.212 m -1 . Further, it was demonstrated that, in coastal waters, optical inhomogeneities with dimensions between 50 m and 200 km obey the power law Sp ε ~ k -P with the parameter P close to two. In turbid or transparent areas, the water extinction index can change by several tenths of a percent with respect to the surrounding water mass. This suggests that the observed nonmonotonic behavior of the power spectra of the water extinction index fluctuations is caused by the outer scale of turbulence, in particular, by the bottom depth at the measurement site. 相似文献
2.
Simultaneous measurements of the diffuse attenuation coefficient, k, and the collinated beam attenuation coefficient, c, were made on a continuous basis at a near-shore site off the north coast of Anglesey, North Wales. A statistical approach to calculating the diffuse attenuation coefficient, k, in coastal waters allowed variations in transparency to be taken into consideration. The ratio of c:k varied throughout the year between approximately 11:1 and 5:1, indicating the changes in the scattering and absorption properties of the water column. The major contribution to coastal turbidity was from the scattering of light by suspended material with the relationship between scattering and absorption being dependent on the nature of the suspended matter. 相似文献
3.
V. I. Man’kovskii G. A. Tolkachenko E. B. Shibanov O. V. Martynov E. N. Korchemkina D. V. Yakovleva I. A. Kalinskii 《Physical Oceanography》2010,20(3):207-230
We present the results of measurements of optical characteristics of waters (the beam attenuation coefficient, volume scattering
function, sea water reflectance, and Secchi depth) and optical characteristics of the atmosphere (aerosol optical thickness,
content of vapors, and the ?ngstr?m exponent) carried out in September 2008 on the oceanographic platform near Katsiveli.
We carried out the comparative analysis of hydrooptical characteristics measured in various years. The optical type of sea
waters in the period of observations is determined. 相似文献
4.
Measurements of underwater irradiance, transparency and Secchi disc depth were carried out in Liverpool Bay during 1974. The depth of the photic zone measured in the green portion of the spectrum ranged from 5 m to 50 m, depending on location and season. Inshore values of photic depth were smaller than those encountered offshore. By mid-summer the depth of the photic zone had reached or exceeded the depth of the sea bed over the whole study area.Consideration was given to the error terms associated with the optical measurements and to the problems of using standard optical relationships in coastal waters. The relationship between Secchi disc depth and the depth of the photic zone could not be taken as constant but was a function of the absorption and scattering properties of the water mass. 相似文献
5.
《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(9):1439-1459
Case 1 waters with high chlorophyll content can be encountered as soon as the nutrient availability is high enough and the terrestrial influence by land drainage is negligible. Offshore oceanic blooms and upwelling zones along arid coasts are instances of such waters. Their bio-optical properties are less documented compared to those of mesotrophic or oligotrophic waters. A coherent set of measurements of bio-geochemical properties (algal pigments, suspended particulate matter), inherent optical properties (absorption and scattering by water bodies and by particulate material), and apparent optical properties (hyperspectral reflectance and diffuse attenuation coefficients) was obtained within the Benguela Current, i.e. in an upwelling area with arid climate and no runoff. These data allow the bio-optical relationships in eutrophic Case 1 waters to be analyzed, and their natural variability to be compared with that previously observed in less productive waters. In addition, a comparison between eutrophic Case 1 waters and yellow substance dominated Case 2 waters can be made, since such waters are also present in the area under investigation. The coherence between the inherent and apparent optical properties is also analyzed via inversion. Despite some deficiencies in their parameterization, the existing bio-optical models for Case 1 waters were proven to be valid such that they can be extended without significant discontinuities toward the domain of high concentration (up to 30 mg m−3). In particular, those models in use for the interpretation of remotely sensed ocean color continue to apply, even if the sensitivity of current algorithms for the chlorophyll retrieval weakens owing to inescapable physical limitations in the case of high concentrations. 相似文献
6.
Physical regularities of water exchange between the North Atlantic (NA) and Arctic Ocean (AO) in 1958–2009 are analyzed on the basis of numerical experiments with an eddy-permitting model of ocean circulation. Variations in the heat and salt fluxes in the Greenland Sea near the Fram Strait caused by atmospheric forcing generate baroclinic modes of ocean currents in the 0–300 m layer, which stabilize the response of the ocean to atmospheric forcing. This facilitates the conservation of water exchange between the NA and AO at a specific climatic level. A quick response of dense water outflow into the deep layers of the NA through the Denmark Strait to the variations in the North Atlantic Oscillation (NAO) index was revealed on the monthly scale. A response on a time scale of 39 months was also revealed. The quick response on the NAO index variation was interrupted in 1969–1978, which was related to the Great Salinity Anomaly. It was shown that transverse oscillations of the Norwegian Atlantic Current significantly influence the formation of intermediate dense waters in the Greenland and Norwegian seas (GNS). The dense water outflow by bottom current (BC) to the deep layers of the NA through the Faroe Channels with a time lag of 1 year correlates with the transversal oscillations of the Norwegian Current front. The mass transport of the BC outflow from the Faroe Channels to the NA can serve as an integral indicator of the formation and sink of new portions of dense waters formed as a result of mixing of warm saline Atlantic waters and cold freshened Arctic waters in the GNS. 相似文献
7.
John Hedley 《Geo-Marine Letters》2012,32(2):173-182
The optical scattering properties of non-spherical calcium carbonate particles were modelled using the finite difference time
domain (FDTD) method. This algorithm is computationally expensive but an implementation running on a standard computer’s graphics
processing unit (GPU) provided up to 40 times speed increase and made feasible several thousand model runs for particles up
to size parameter 33 (4 μm for a wavelength of 376 nm in water). The model evaluates all coefficients of the single-particle
Mueller matrix and, when applied to spheres in this size range, compares closely to Mie theory. The modelled unpolarised and
polarised angular irradiance scattering from elongate calcium carbonate spicules displayed many differences from that of spheres
of equivalent volume. Scattering features were observed that are not immediately obvious consequences of spicule geometry.
The extinction efficiency of these particles is also less than that of spheres of equivalent volume. These results suggest
both potential consequences of the non-sphericity of particles on instrument calibration and radiative transfer modelling,
and opportunities for information extraction by polarimetry. 相似文献
8.
太湖水中可溶性有机质,悬浮质和浮游藻类色素的光学特性的测定 总被引：1，自引：0，他引：1
本文着重分析了分光光度计测定的太湖水体中悬浮质、可溶性有机质和浮游藻类色素在可见光波段(400nm—700nm)的吸收;讨论了对池塘及两种高等植物色素吸收的对比测定;并利用迭代回归方法对测试样品的散射效应进行了订正。结果表明:(1)可溶性有机质吸收在短波部分较强;并且随着入射波长的增大,吸收几乎呈指数律减小,减小速率比国外海洋中的测量结果小。(2)水中悬浮质对光具有较强的散射作用,散射系数约按入射波长呈倒数变化。(3)不同植物中的色素的吸收光谱有明显差异。此外,利用所测数据,本文还对冬季太湖水体的反射光谱和向下光照衰减系数进行了数值计算,表明该水体对入射光照的反射和衰减与纯净水情况有很大差别,目此,太湖水光学特性研究中必须考虑水中物质的影响。 相似文献
9.
The characteristics of shallow-water reverberation are often controlled by scattering from the seabed. While scattering mechanisms are understood in general, the state-of-the-art falls far short of predicting the correct angular and frequency dependence of scattering in a given region. A series of acoustic and supporting geoacoustic measurements were conducted over a large area in the Straits of Sicily in order to study seabed scattering in a complex littoral environment. The hypothesis was that exploiting direct path reflection coefficient measurements, in conjunction with the scattering measurements, could help illuminate the underlying scattering mechanisms. The sediment at the seabed interface was found to be a fine silty clay with nearly uniform properties across the area. Notwithstanding this spatial homogeneity, 1-6-kHz reflection and scattering measurements showed significant spatial variability. The coupled reflection-scattering approach resolved this apparent discrepancy, revealing that the reflection and scattering processes are largely controlled by the sediment properties below, rather than at, the water sediment interface. Measurements at 3600 Hz show that site-to-site variability is in part controlled by the thickness of the silty-clay layer. Layers up to 10 m below the water sediment interface contribute to the scattering at 3600 Hz. 相似文献
10.
利用单波束测深仪和蚌式取样器进行了日照石臼港扩建码头西侧约50km~2海域1:2 000~1:10 000的水深地形测绘和底质分析工作。调查结果表明,日照港西部海域可分4个水深区,其地形和沉积特征如下:1)航道区,浅水航道区等深线平行于码头岸线,水深11m,经过疏浚已形成向南倾斜的四级阶梯地形,疏浚中心处水深24m。航道区底质以分选中等的砾砂为主;2)港池区,水深6 m,等深线与港池岸线平行,水深向南渐增,海底地形平坦,坡降比3‰。底质以分选较好的粉砂和砂质粉砂为主,近岸有少量分选较差的泥质砂质砾;3)涛雒-付疃河口区,水下三角洲地形明显,5m以浅等深线呈弧形向东南方向凸出,坡降比最大可达14.2‰,底质类型为分选极好的砂和粉砂质砂;4)浅海区,海底地形平坦,平均坡降比1.9‰,6~10m等深线呈NE-SW向平行向外海增大,近南扩码头端向东偏转,底质类型为分选好的砂质粉砂和粉砂,并呈平行于海岸线向深水区呈粗-细-粗的带状分布。底质类型分布与水深条件基本吻合,但深水区出现的底质粗化现象,分析认为可能与南扩码头的挑流作用有关,海底沉积物呈向南运移趋势。 相似文献
11.
This paper suggests a new version of the Secchi disk theory which shows a connection between Secchi depth measurements and
inherent optical properties (IOP) of water such as the extinction coefficient, the single scattering albedo, and the backscattering
coefficient. Ways around Preisendorfer’s objection to using measurements of the Secchi depth for determining the IOP are proposed.
This theory is compared with a marine experiment and its accuracy under different conditions is estimated. 相似文献
12.
Light scattering profiles and water samples for filtration of suspended particulate matter were obtained during fall, 1973, from Ice Island T-3, then located about 50 miles north of Ellesmere Island. The profiles reveal almost no variability in scattering, either in the water column, or in time during our two weeks of field work. Gravimetric analysis of the filtered suspended particulate matter shows that mass concentrations are low, averaging about 7g l–1, and that they too remain very constant. The four water masses present in the Arctic Ocean could not be distinguished by our observations of light scattering and mass concentration of suspended particulates. 相似文献
13.
南沙群岛海区毛颚动物的昼夜垂直移动 总被引：10，自引：2，他引：10
对1997年11月和1999年4月、7月在南沙群岛海区3个昼夜连续测站采集的毛颚动物样品进行了研究。结果表明，这些水域的毛颚动物的昼夜垂直移动可以划分为3个类型：种类作显著移动，不作显著移动和仅在夜晚移动。作为昼夜垂直移动显著的种类，又可以把它们划分为：（1）种类在整个水柱移动；（2）种类在上层（0－60m）移动；（3）种类在中层（60－100m）移动。作为昼夜垂直移动不明显的种类，又可以把它们分为：（1）种类分布在于上层（0－60m）。（2）种类分布于底层（100－200m）。种类在白天下降或附着在海底物体上，仅在夜晚移动。光照，水温，食物和种类特征是影响本水域毛颚动物昼夜垂直移动的重要因素。 相似文献
14.
Light scattering and size distribution of particles in the surface waters of the North Pacific Ocean 总被引：1，自引：0，他引：1
The volume scattering function and size distribution of suspended particles in the surface water were determined in the North Pacific. The relationship between the scattering coefficient estimated from observed volume scattering function and cross-section concentration of the particles greater than 2.4m in diameter was found to be linear in both northern and southern regions of central North Pacific. Difference in the constant of proportionality between two regions, however, was very great. Moreover the constant in the southern region was too large compared with the values obtained by the Mie theory. This is considered to be due to the fact that particles smaller than 2.4m which were not measureable by the Coulter Counter, were neglected in the calculation of cross-section concentration. If small particles are taken into consideration, total cross-section concentration and scattering coefficient in the two regions tend to follow a linear relation. From the correlation between the scattering coefficient computed from size distribution and the volume scattering function, the refractive index of particles was estimated to be 1.03–1.05. By the same procedure, the refractive index of particles in Tateyama Harbour where the water was very turbid, was estimated to be also 1.03–1.05. This is in contrast to the result for the refractive index of particles originating from the river which flows into the harbour. This index was found to be 1.10–1.20. 相似文献
15.
1 IntroductionKnowledge of suspended particle size and distri-bution is the key elements for better understandingthe sediment transport processes ( Wang et al.,2004), primary production (Ning et al., 2004),water quality controlling and pollution predictio… 相似文献
16.
根据2013年11月、2014年2月、5月、9月在南麂列岛国家海洋自然保护区海域进行生物资源调查所获得的资料,分析了南麂列岛海域蟹类种类组成、优势种、生物多样性等群落结构特征,并定量分析了群落结构与水文环境因子之间的关系。结果表明,周年4个季度月调查共鉴定出蟹类21种,隶属7科、12属,其中优势种为三疣梭子蟹（Portunus trituberculatus）、日本蟳（Charybdis bimaculata）和双斑蟳（Charybdis bimaculata）3种。不同季节的蟹类种类组成差异较大,而优势种类组成变化较少,其中,以秋季的蟹类种类数最多,冬季最少。从不同水深区域的渔获种类分布趋势来看,蟹类种类以20~30 m水深带较多,30~40 m水深带较少。夏季多样性指数低于其他季节,以水深来看,多样性指数在10~20 m水深带较高,30~40 m水深带较低,蟹类多样性指数与水深呈反比。根据冗余分析认为,水深、水温和盐度是影响调查海域蟹类种类组成和群落结构特征的主要环境因子。 相似文献
17.
We analyzed hydrographic data obtained monthly by the Iwate Prefectural Fisheries Laboratory during 1977–1981. Our attention was focussed on the classification of waters based on the Temperature-Salinity (T-S) scatter diagram analyses, and on the extraction of the mean state of their distribution for each season. The water system was defined as all waters occupying some specific region on the T-S plane, and the mean state for each season was expressed by the distribution of the mode water systems (i.e., the most commonly occuring water system).Because of the coexistence of the Tsugaru Warm Current, the Oyashio and the Kuroshio, and their large seasonal variability, the sea waters had a wide variety of T-S combinations. The detailed T-S scatter diagram analyses allowed us to classify the waters into six water systems. A time-longitude diagram of water systems and the distribution of mode water systems are presented. The latter showed clear seasonal variations of the Tsugaru Warm Current and the Oyashio.Though the water system analysis was successfully able to present the distribution of the various waters in the Sanriku Coastal Area and to clearly extract the mean state of sea conditions, it was found that the classification of water systems on the T-S plane was not complete in all cases for this area. 相似文献
18.
This paper addresses the question of the eventual control of barium concentration in seawater by an equilibrium with barite. For this, we have used a new thermodynamic model to compute the barite saturation index of ocean waters, mainly from GEOSECS data. Our results show that equilibrium between barite and seawater is reached in a number of places: cold surface waters of the Southern Ocean, waters at intermediate depths (2000–3500 m) in the Pacific, deep waters (2000–3500 m) of the Gulf of Bengal. The only samples for which a slight barite supersaturation is found are the surface waters at GEOSECS station G89 in the Weddell Gyre. Besides these locations, the rest of the world's oceans is undersaturated, as was established by Church and Wolgemuth [Church, T.M., Wolgemuth, K., 1972. Marine barite saturation, Earth Planet. Sci. Lett. 15 35–44.]. There is a return to undersaturation of the water column at depths of about 3500 m in the Pacific and of about 2500 m in the Southern Ocean. The reverse is found for GEOSECS station 446 in the Gulf of Bengal for which the highest Ba concentrations can be found at depth: surface waters are undersaturated and equilibrium is reached below 2000 m. Finally, we briefly discuss the role of biogenic and inorganic processes on barite formation in the ocean as well as the influence of strontium substitution in marine barites. 相似文献
19.
浮游藻类是海水中的重要组成成分,对其固有光学特性的研究有助于深入了解水体光学的辐射传输。在过去的30年中,大量的研究都集中在藻类吸收特性上,缺少对其散射特性的认识。本文利用分光光度计设计了在实验室中测量含颗粒水体散射和后向散射特性的方法,并利用标准球形颗粒对该方法的可行性进行验证,结果表明,在400~700 nm范围内,散射测量结果与理论值的一致性较好,最大误差小于3%,而后向散射测量结果在蓝紫光处的一致性较好,在近红外波段处有一定误差。运用这两种测量方法对东中国海常见的赤潮藻种中肋骨条藻Skeletonema costatum和东海原甲藻Prorocentrum donghaiense进行测量,结果显示:中肋骨条藻与东海原甲藻的散射系数幅值相近但谱形差异较大,前者随波长增加散射强度递减,后者则相反;在色素吸收较强的波段,两者散射强度均出现与其它波长位置变化趋势相反的情况,这主要是受细胞物质物理性质的影响。两者的后向散射差异较小,但可以看出其谱形受色素吸收的影响很大,在幅值上,东海原甲藻略高于中肋骨条藻,在550 nm处分别为0.001 74,0.001 43 m2/mg(以藻类叶绿素a浓度归一化),后向散射概率分别为1.104%和0.723%。 相似文献
20.
A combination of δ~(18)O and salinity data was employed to explore the freshwater balance in the Canada Basin in summer 2008.The Arctic river water and Pacific river water were quantitatively distinguished by using different saline end-members.The fractions of total river water,including the Arctic and Pacific river water,were high in the upper 50 m and decreased with depth as well as increasing latitude.In contrast,the fraction of Pacific river water increased gradually with depth but decreased toward north.The inventory of total river water in the Canada Basin was higher than other arctic seas,indicating that Canada Basin was a main storage region for river water in the Arctic Ocean.The fraction of Arctic river water was higher than Pacific river water in the upper 50 m while the opposite was true below 50 m.As a result,the inventories of Pacific river water were higher than those of Arctic river water,demonstrating that the Pacific inflow through the Bering Strait is the main source of freshwater in the Canada Basin.Both the river water and sea-ice melted water in the permanent ice zone were more abundant than those in the region with sea-ice just melted.The fractions of total river water,Arctic river water,Pacific river water increased northward to the north of 82°N,indicating an additional source of river water in the permanent ice zone of the northern Canada Basin.A possible reason for the extra river water in the permanent ice zone is the lateral advection of shelf waters by the Trans-Polar Drift.The penetration depth of sea-ice melted waters was less than 30 m in the southern Canada Basin,while it extended to 125 m in the northern Canada Basin.The inventory of seaice melted water suggested that sea-ice melted waters were also accumulated in the permanent ice zone,attributing to the trap of earlier melted waters in the permanent ice zone via the Beaufort Gyre. 相似文献