青岛陆上观测点的气溶胶光学厚度特征分析及与渤海气溶胶光学厚度的比较

阐述了气溶胶散射对太阳光衰减的影响和对观测数据的统计分析.作者使用手持式五波段太阳光度计和臭氧监测仪对青岛崂山区陆域和渤海海域的大气衰减进行了较长时间的观测.分析表明,对可见光和近红外波段电磁渡的大气衰减贡献最大的是气溶胶散射,气溶胶散射的光学厚度随波长的增大而减小,但是它在大气总光学厚度中占的比例随波长的增大而增加.在青岛崂山区冬季,对应于440nm波长的气溶胶散射光学厚度主要分布在0.4～0.6和1.5～1.6区间,浑浊度系数α主要分布在0.15～0.45区间,埃斯特朗指数β主要分布在1.0～1.4区间.从时间上看,α和β在1d内的变化不大,但逐日变化非常显著.与晴天相比,青岛崂山区冬季雾天的气溶胶散射光学厚度增加了大约一倍,较大的浑浊度系数和较小的埃斯特朗指数表明,雾天的大气具有气溶胶散射的光学厚度大、粒子浓度大和粒径尺度大的特点.通过与海上观测数据的比较可见,青岛崂山区陆地冬季在雾天时的气溶胶分布与渤海夏季时相似,青岛崂山区陆地冬季在晴天无云时的气溶胶分布与渤海秋季时相似.     

流式细胞测定技术在海洋生物和海洋生态环境监测研究中的应用

流式细胞测定技术 ( flow cytometry)是一项现代化的生物学测定和生态学观测的高新技术 ,通过对细胞的光散射和不同荧光的多参数同步测定 ,可对单细胞海洋生物等颗粒物根据海洋自然水体中颗粒物的性质进行分离与监测图 1　流式细胞测定技术在海洋生态系观测中的应用 [1]进行快速、精确地定性和定量分析。光散射(包括前角光散射和侧角光散射 )可对颗粒物的微形态特征进行测量 ,诸如颗粒物的粒径、质地、光学性质等 ,可测定的颗粒物粒径范围在 0 .5～ 1 50μm;同时可通过对单细胞藻类所含色素的自荧光测定来鉴别其所含色素的种类和含量 ,从而…     

水下激光散射仪的研制

一、前言海洋光学发展至今已经成为一个范围广泛、具有巨大潜力的重要学科。光在水中的传输特性,始终是人们感兴趣的课题。散射和吸收是决定光在海水中传播的基本过程。海水对光的散射是比较复杂的,这是由于海水中悬浮粒子的大小范围很广,粒子的散射特性是与粒子的大小相对于光的波长之比有关,同时海水对光的散射还与粒子的性质和数量有关。此外,它们又随着时间而变化,并受制于水文要素。因此,必须对光散射作比较详细地研究,并对各海区的光散射特性作现场调查。海水光散射的测量对水下照相、水下电视、水下伪装、水下照明工程、水下捕捞、遥感沿岸水深和水色、海水表     

高生产力区LISST-100和OBS对悬浮颗粒物测量的比较研究

LISST-100通过激光前向散射测量32个粒径的悬浮颗粒物体积分数,OBS通过接受后向散射光强测量浊度,浊度反映水体浑浊程度,可用其变化代表悬浮颗粒物浓度变化。利用LISST-100和OBS于浙江外海高生产力区对悬浮颗粒物进行周日变化的同步观测,结果表明,浮游生物高生物量水体中,LISST-100能够测量出悬浮颗粒物体积分数的变化,由于颗粒物体积与其粒径成立方关系,其对于大颗粒物质变化比较敏感;OBS只能反映部分浓度变化,OBS接收的后向散射量强度取决于颗粒物后向散射截面的影响,因此对于小颗粒悬浮物质更为敏感,对大颗粒物质变化不敏感。无机小颗粒占优水体中LISST-100和OBS对于悬浮颗粒物的测量均较为理想。在悬浮颗粒物组分复杂的水体中,采用LISST-100有其优势,它可以获得不同粒径组分的体积分数,而OBS则适用于更小粒径范围的水体,主要是因为其对大粒径的浮游生物不敏感。     

海水黄色物质光吸收特性实验研究

实验测量了干样配制的不同浓度黄色物质水溶液、实验室藻类培养和胶州湾水域黄色物质水样的光吸收特性。测量结果表明，海水黄色物质光吸收系数与波长是单调变化关系，即不存在“波峰”和“波谷”；在蓝紫光波段，海水黄色物质光吸收比海水自身、海洋叶绿素和悬浮粒子光吸收大，它是海洋中对该波段光吸收起着主导作用的物质；海水黄色物质光吸收系数与波长呈指数函数关系，其指数斜率s数值范围分别为：胶州湾水域在0.0131-0.0180nm^-1，实验室配制、培养样品是在0.0105-0.0139nm^-1。该研究为海水黄色物质含量的遥感探测提供了基础性实验依据。     

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

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。     

黄东海海区悬浮颗粒物后向散射系数和后向散射比的空间分布规律研究

悬浮颗粒物在海洋光学特性中扮演着重要角色,后向散射系数是水色遥感反演中最主要的基础参数之一,因此对于悬浮颗粒物后向散射系数的研究具有重要意义。利用2003年4月黄东海春季航次测量的吸收、衰减和后向散射数据,研究该区域悬浮颗粒物后向散射系数和后向散射比的光谱特征以及空间分布规律。研究结果表明颗粒物后向散射系数光谱呈指数衰减且在垂直方向上与深度正相关;后向散射比的光谱具有波段特征;由于近岸颗粒物浓度大、粒径小,远岸颗粒物浓度小、粒径大以及湍流扰动的影响,导致后向散射系数和后向散射比呈现出在近岸海域较大而在远岸海域较小的空间分布规律。     

纳米碳纤维红外消光数值计算

为探讨纳米碳纤维作为烟幕粒子的红外消光特性,基于电磁场理论建立了细直的纳米碳纤维感应电流积分方程,并利用矩量法进行了求解,导出了纳米碳纤维散射场及吸收、散射和消光截面的计算式.通过与变分法的计算结果相比较,表明了该方法的有效性.利用该方法数值分析了纳米碳纤维红外消光截面与入射场波长、入射角、纤维长度和半径的关系,计算结果为纳米碳纤维用于红外烟幕干扰提供了理论依据.     

定程法测量海洋沉积物悬浮液声衰减

本文尝试用脉冲定程法测量海洋沉积物悬浮液声衰减。借用泥沙粒度分析中所用的沉降法,对每个样品测量7种不同粒径范围下的声衰减与体积浓度之间的关系。实验表明,文献[1]在考虑海洋沉积物悬浮液声衰减时引入悬浮粒子的形状系数k是必要的。并由k值粗浅地讨论了该海区沉积物的特征。     

太湖悬浮质对湖面反照率及水体光吸收的影响

本文根据Mie散射理论,利用太湖水中悬浮质粒径谱分布的实测资料,计算了湖水的光散射相矩阵,消光系数和吸收系数等光学参量,并采用Monte Carlo方法,研究了湖面反照率和水体光吸收以及太阳高度角、入射光波长、底泥反射、悬浮质浓度和粒径分布变化的影响。数值计算结果表明:在研究湖泊水体对太阳辐射能量的反射和吸收时,水中悬浮质是一个不可忽视的重要因素。     

各向异性海面全极化微波双站散射的仿真与分析

为了解各向异性随机粗糙海面的微波双站散射机制及其特性,本文利用解析近似的积分方程模型以及一种改进的半经验海浪谱模型实现了对各向异性随机粗糙海面的全极化微波散射仿真模拟,并与卫星观测数据、经验的地球物理模式函数及已有的解析近似散射模型仿真结果进行了对比,验证了仿真结果的可行性和准确性。利用该模型分析了入射波频率、入射角、极化方式、海面风速及风向等参数对各向异性海面双站散射的影响。模拟结果表明,在不同的入射角、散射角及方位角等观测几何条件下,海面不同波段的双站散射表现出不同的空间散射特性,且对风速、风向等海面动力学参数表现出不同的敏感性,以L波段为例,海面向后半球双站散射在各个极化方式下都对风速较为敏感,而在同极化方式下,其对风向的响应在中低风速和高风速条件下相反,整体而言,低风速下海面双站散射对风向更为敏感。这表明对于海面动力参数的反演,双站散射可以提供比传统单站雷达后向散射更丰富的物理信息。本文探讨了各向异性海面微波双站散射特性,为基于主动式及分布式微波传感器的海洋动力参数遥感反演提供了理论分析基础。     

高光谱碘分子和双边缘多普勒测风激光雷达技术比较

对采用原子滤波器的激光雷达技术和双边缘技术的灵敏度和误差进行了详细的讨论。对于纯 Rayleigh散射 ,双边缘系统的灵敏度高于基于碘分子的激光雷达系统 ,而对于 Rayeigh- Mie混合信号 ,双边缘系统通过采用特殊工作点的办法 ,有效解决 2种信号响应不同的问题 ;但同时该工作点的选取使得系统灵敏度降低 ,误差增加。对于后向散射比不是很大 (<10 )的情况下 ,误差可以控制在1m/s以内 ,完全可以满足测量要求 ,因此对于对流层顶部和平流层测风很适合。基于碘分子的激光雷达系统利用碘分子的高吸收性对 Rayleigh- Mie信号有效的进行分离 ,并且灵敏度随着后向散射比的增加而增加 ,从而对底层大气的探测特别有利。     

Field studies of the correlation between the atmospheric aerosol content and the light polarization at the zenith of the daytime sky

Results of simultaneous measurements of the direct solar radiation flux and of the degree of polarization of visible light scattered at the zenith at a different albedo of the underlying surface covered with snow after heavy snowfalls or having no snow cover are analyzed. The possibility of monitoring air turbidity on the basis of polarimetric measurements is confirmed. A procedure of remote detection of the effect of solar light polarization on atmospheric aerosol is proposed and implemented.     

Vertical spatial coherence of backscatter from bubbles

A basic formalism is developed to treat the vertical spatial coherence of backscatter from wind-generated microbubbles beneath the ocean surface. This formalism treats signals multiply scattered by the sea surface and the subsurface scatterers, as well as absorption in the bubble layer. Approximate solutions are obtained for the case of narrow beamwidth sources and are applied to study the influence of measurement system and environmental parameters on coherence. Using bubble densities derived from acoustic backscatter data, the coherence is found to depend strongly on source frequency and beam pattern. The primary environmental effect is due to the increase in both bubble density and penetration depth below the surface that occurs with increasing windspeed. At high wind speeds, the vertical coherence is sufficiently dependent on the scatterer depth distribution to provide a viable means of studying this phenomenon.     

Submersible holocamera for detection of particle characteristics and motions in the ocean

A submersible holographic camera has been developed for measuring the particle distributions, characteristics and motions within a sample volume in the ocean. Its main purpose is to provide data on the spatial distribution, size, shape, orientation, inter-particle relationships, turbulence, local shear and relative motion due to swimming and sinking of plankton. This battery powered, modular, self-contained system is remotely operated by a PC through fiber optic links. Data from on-board environmental sensors are used to select locations for recording holograms and relating the images to broader scale physical structures. The holocamera also has a buoyancy control system that allows deployment as a neutrally buoyant drifter or in a slow profiling mode. The instrument is currently configured for in-line holography, but it has been designed to be readily adaptable to off-axis holography. The cylindrical sample volume is 6.3 cm in diameter and its length can be varied from 10 to 68 cm. The light source is a pulsed ruby laser chosen predominantly because zooplankton are typically less sensitive to red light. The laser has independent dual flashlamps for maximum flexibility in selecting delay between exposures. About 300 single or multiple exposure holograms can be recorded during a single deployment. Data such as particle size, shape, orientation, distribution in space and velocity are obtained by reconstructing the holograms, scanning them with a video camera equipped with a microscope objective, digitizing the images and analyzing relevant data. Several recent field tests have demonstrated the system reliability and resolution. Particles with sizes as small as 10 μm and details on cell structures of larger particles in the 3–5 μm range could be identified and used for identifying and categorizing the particles. Sample single and double exposure images, the latter for measuring motion, and sample spatial distributions are provided. Methods for mapping the liquid velocity distribution are addressed briefly. Parameters affecting the image resolution and location in space, such as particle density, distance from the film plane and focus are discussed and demonstrated.     

Utilizing High-Frequency Acoustic Backscatter to Estimate Bottom Sand Ripple Parameters

In some applications of underwater acoustics, it is important to know the ripple structure on shallow-water sediments. For example, the prediction of buried target detection via sound scattering by ripples depends critically on the ripple height and spatial wavelength. Another example is the study of sediment transport, where knowing the ripple structure and its evolution over time helps to understand the forcing on the bottom and the response of sediments. Here, backscatter data from a 300-kHz system are used to show that ripple wavelength and height can be estimated from backscatter images via a simple inversion formula. The inversion results are consistent with in situ measurements of the ripple field using an independent measurement system. Motivated by the backscatter data, we have developed a time-domain numerical model to simulate scattering of high-frequency sound by a ripple field. This model treats small-scale scatterers as Lambertian scatterers distributed randomly on the large-scale ripple field. Numerical simulations are conducted to investigate the conditions under which remote sensing of bottom ripple heights, wavelength, and its power spectrum is possible.      

Measurement of seabed topography by multibeam sonar using CFFT

A precise ocean bottom map for ocean surveying and dredging is desired. Especially in dredging, it is essential to know the seabed topography in real time without being affected by scatterers (for example floating sand and mud) in the seawater during work. To meet these requirements, the multi-narrow-beam sonar system (MBSS) has been developed. The MBSS forms beams with the use of the complex fast Fourier transform (CFFT) algorithm. In the MBSS, arithmetic mean processing is employed to eliminate echo from scatterers and the measurement error due to the oblique incident angle is reduced by peak value detection processing. By using these processes, an ocean bottom map can be accurately obtained. It is both theoretically and experimentally shown that the distribution of echo intensity from scatterers is approximated by the Rayleigh probability density function. The arithmetic mean of four to eight successively received echoes from scatterers reduces the variance of the echo intensity distribution by 6 to 12 dB.     

Back-scattering from rough sea surface with foams

INTRODUCTION Eleetromagnetie baek一seattering from randomly rough surfaee driven by wind,and funetion-al dePendenee on wind sPeed and direetion,and the eharaeteristie Parameters of sea surfaee havebeen interested in the ocean remote sensing.One of the approaehes to eleetromagnetie seatteringfrom randomly rough surfaee 15 the Kirehhoff approximation(KA),and the geometrie opties 50-lution in high frequeney 15 used by the stationary phase method(Bass and Fueks,1979) .TheKA solution 15 val…     

Modeling high-frequency acoustic backscattering from gas voids buried in sediments

It was found in a previous paper that strong acoustic backscattering from a soft sediment in Eckernförde Bay, Germany, is caused by scatterers buried beneath the sea floor. The scatterers are methane gas voids of nonspherical shape. This paper models backscattering due to such gas voids. Scattering cross sections of oblate spheroids are calculated to approximate those of gas voids. Proper statistical averages are taken to make model/data comparisons. It is found that this single scattering model compares favorably with measured acoustic backscattering data at 40 kHz. In the model, density and spatial distribution of gas voids are derived from limited core data.     

Measurements and modeling of low-frequency near-surface scattering statistics

High-resolution acoustic measurements of low-frequency near-surface backscattering at low grazing angles have been made in the open ocean using vertical arrays of coherent sources. Over the range of wind speeds (4-18 m/s) encountered, the normalized data amplitudes exhibited variable non-Rayleigh behavior, from near Rayleigh in the highest sea states to near lognormal in low-to-moderate sea states. Seven probability density function (pdf) models were fit to the data, with the three-component Rayleigh mixture providing the most consistent fits and the least errors. One pdf model, the Poisson-Rayleigh, provided not only good fits to many data sets, but also physical insights into the scattering process. This model's estimates of the expected number of discrete scatterers ranged from 200/km/sup 2/ at low wind speeds to 2000/km/sup 2/ at high wind speeds, consistent with the expected densities of fish and subsurface bubble clouds, respectively. These results are encouraging with regard to developing physical models capable of using local results (such as these) to accurately predict long-range reverberation and clutter statistics.