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1.
The operation of a lidar intended for clear air turbulence (CAT) positioning on the basis of the backscatter enhancement (BSE) effect is analyzed using a turbulence model with a power-law spectrum. Systematic distortions occurring due to a need to regularize the lidar positioning problem solution are estimated. It is shown that the effect of molecular viscosity of air on the positioning result can be neglected if the wave parameter, which characterizes the diffraction manifestation, is higher than 3. This corresponds to sounding ranges of more than 1 km for optical or UV lidars. The analysis results show that the BSE lidar positioning accuracy weakly depends on the exponent in the turbulence spectrum in regions of severe turbulence. The results can justify a physical experiment for the design of an aircraft system for the lidar detection of CAT regions ahead of the flight course. 相似文献
2.
A. S. Gurvich 《Izvestiya Atmospheric and Oceanic Physics》2014,50(2):143-151
The possibility of lidar positioning of regions with higher clear-air turbulence (CAT) is shown. The turbulence is indicated by air density fluctuations generated by it. A scheme with a lidar based on using the backscattering enhecement (BSE) effect in a turbulent medium is considered. A stable solution of the positioning problem is obtained using the statistical regularization method. As is shown on models, CAT regions that are dangerous for civil aviation flights can be detected using such a lidar. 相似文献
3.
V. A. Korshunov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(5):618-633
A scheme of interpreting the data of two-wavelength lidar sounding is proposed. The scheme is based on functional relationships between the lidar ratios and between some integral characteristics of aerosol and the ratio of the backscattering coefficients at the sounding wavelengths. The AERONET data, results of contact aerosol measurements and multiwavelength lidar sounding, and the OPAC aerosol model are used to find these functional relationships, which are statistical in character. Analysis of data is made separately for continental, dust, oceanic, and smoke aerosols. Backscattering for mineral aerosol fractions are calculated for a model of randomly oriented spheroids. A numerical experiment shows that the errors in determining a number of integral parameters of aerosol (extinction coefficient, characteristic radius of particles, volume concentrations) that are due to the statistical straggling of lidar ratios and other specified integral characteristics are no greater than 32% if the optical thickness of the sounding layer is no greater than 1. 相似文献
4.
O. A. Bukin K. A. Shmirko A. Yu. Maior A. N. Pavlov S. Yu. Stolyarchuk G. I. Kornienko D. V. Erofeev 《Izvestiya Atmospheric and Oceanic Physics》2010,46(2):178-183
The distribution functions of atmospheric aerosol obtained on the basis of lidar sounding and photometric measurements over
marine water areas in continental and transition zones are analyzed. Changes in the microphysical parameters of the distribution
function in the continent-ocean transition zone with height are considered on the basis of data taken from three-frequency
lidar sounding. Specific features of changes in the particle size distribution with height during intense dust storms and
records of volcanogenic aerosol in the tropopause region in the summer of 2008 are described. 相似文献
5.
高光谱分辨率激光雷达(HSRL)大气温度测量模拟 总被引：1，自引：0，他引：1
激光雷达探测大气温度通常采用探测大气分子瑞利散射的方法,这种方法由于低层气溶胶的存在,一般只能探测高空（约12km以上）的大气温度,而探空气球又存在不能获取连续数据和定位性差的问题.文章给出了利用高光谱分辨率激光雷达探测大气温度的方法,并对此方法作了理论模拟.结果表明此方法可用于低层大气温度垂直剖面探测. 相似文献
6.
《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(1):143-153
Models and laboratory experiments show that zooplankton may locate food more easily in turbulent waters, but whether plankton seek or avoid turbulence in the ocean is an open question. It is difficult to measure turbulence and plankton simultaneously and with the necessary spatial resolution using traditional methods (nets and airfoil shear sensors). Acoustics is commonly used to survey zooplankton abundance and recent studies have shown that stratified turbulence can also be a significant source of sound scatter. This may seem like more of a complication than a boon for those aiming to use acoustics to observe plankton in turbulence. We present acoustic data, however, that show that zooplankton and turbulence can be observed simultaneously with a single 307 kHz sounder. The different natures of the two targets (discrete targets versus a volume effect) allow them to be distinguished. The key is sampling the same targets at multiple ranges. The volume scattering strength of a discrete target will increase as the target nears the sounder, because the volume sampled decreases. Turbulence, as a volume scattering effect, has little range dependence to its volume scattering strength. 相似文献
7.
A. G. Luchinin 《Izvestiya Atmospheric and Oceanic Physics》2010,46(4):492-498
We have studied the influence of a roughed sea surface and the dispersion of photons over pathlengths on the time characteristics
of a pulsed oceanologic airborne lidar. We have derived equations describing the first two temporal moments of a return signal
for two types of lidar (a lidar with an isotropic receiver directional pattern and a lidar with an extremely narrow receiver
pattern). It is shown that the delay of the return signal and its effective width depend substantially on both the characteristics
of the lidar itself and on the parameters of the sea-surface roughness and inherent optical properties. 相似文献
8.
9.
This article studies the effect of airborne lidar (surface) elevation data on the classification of multispectral IKONOS images over a coastal area. The lidar data and IKONOS images are treated as independent multiple bands to conduct the classification. To do so, the lidar elevation data is first resampled to the same ground spacing interval and stretched to the same radiometric range as the IKONOS images. An unsupervised classification based on the ISODATA algorithm is then used to determine a class schema of six classes: road, water, marsh, roof, tree, and sand. Training sites and checking sites are selected over the lidar-IKONOS merged data set for the subsequent supervised classification and quality evaluation. The complete confusion matrices and average quality indices are presented to assess and compare the classification results. It is shown that the inclusion of the lidar elevation data benefits the separation of classes that have similar spectral characteristics, such as roof and road, water and marsh. The overall classification errors, especially the false positive errors, are reduced by up to 50%. Moreover, by using the lidar elevation data, the classification results show more realistic and homogeneous distribution of geographic features. This property will benefit the subsequent vectorization of the classification maps and the integration of the vector data into a geographical information system. 相似文献
10.
Combining Lidar Elevation Data and IKONOS Multispectral Imagery for Coastal Classification Mapping 总被引：1，自引：0，他引：1
This article studies the effect of airborne lidar (surface) elevation data on the classification of multispectral IKONOS images over a coastal area. The lidar data and IKONOS images are treated as independent multiple bands to conduct the classification. To do so, the lidar elevation data is first resampled to the same ground spacing interval and stretched to the same radiometric range as the IKONOS images. An unsupervised classification based on the ISODATA algorithm is then used to determine a class schema of six classes: road, water, marsh, roof, tree, and sand. Training sites and checking sites are selected over the lidar-IKONOS merged data set for the subsequent supervised classification and quality evaluation. The complete confusion matrices and average quality indices are presented to assess and compare the classification results. It is shown that the inclusion of the lidar elevation data benefits the separation of classes that have similar spectral characteristics, such as roof and road, water and marsh. The overall classification errors, especially the false positive errors, are reduced by up to 50%. Moreover, by using the lidar elevation data, the classification results show more realistic and homogeneous distribution of geographic features. This property will benefit the subsequent vectorization of the classification maps and the integration of the vector data into a geographical information system. 相似文献
11.
海雾生成过程中平流、湍流和辐射效应的数值试验 总被引：11，自引：0，他引：11
利用相对湿度方程,结合数值模式研究了在海雾生成过程中平流、湍流和辐射的效应。结果表明,海雾生成的主要“推动力”是长波辐射冷却,湍流冷却在低层主要发生在平流的初始阶段。随着时间的推移,湍流对低层大气很快变为起加热作用,不利于海雾的生成。湍流和辐射效应在低层大气中符号相反(仅在海雾生成的初始阶段符号相同),量级相同,在高层大气中湍流和辐射效应符号相同,但辐射效应占优势。湍流效应和辐射效应是影响海雾生成的主要因素,平流直接作用似乎不大。平流、湍流和辐射效应及其总效应均随时间推移而减小。另外,还初步研究了风速大小和海温高低对平流、湍流和辐射效应及海雾生成的影响。 相似文献
12.
Direct measurements of eddy diffusivities for momentum K m and heat K h by Doppler radar and by a radio acoustic sounding system in the upper troposphere and lower stratosphere were used to examine the applicability of three Reynolds-averaged Navier-Stokes (RANS) schemes of stratified turbulence in the environment: the E — ? turbulence scheme modified for stratified flows, the algebraic two-parameter E — ? Reynolds-stress scheme, and the three-parameter \(E - \varepsilon - \overline {\theta ^2 } \) turbulence scheme. All turbulence parameters-the turbulent kinetic energy (E), the dissipation rate (?), and vertical profiles of potential temperature (atmospheric stability) and mean wind velocity-were derived from direct measurements for all three turbulence schemes. It is shown that the profile of the vertical diffusivity of momentum (K m ) obtained from the three-parameter RANS turbulence scheme agrees well with its directly measured analog. The profile of K m calculated by the two-parameter turbulence schemes fits measurements rather qualitatively. 相似文献
13.
O. S. Ermakova I. A. Kapustin V. V. Papko 《Izvestiya Atmospheric and Oceanic Physics》2008,44(5):583-593
The dynamics of a layer of turbulence excited by a ribbed oscillating grate in homogeneous and stratified fluids is investigated experimentally. The time dependences of the thickness of the region encompassed by turbulence in a homogeneous fluid are obtained. On the basis of a semiempirical turbulence theory, it is shown that the time dependence of the coordinate of the turbulent-front position can be described by a power function. A satisfactory agreement between the experimental and theoretical dependences is obtained. Different regimes of turbulent-layer dynamics in a fluid with salinity stratification are investigated. The results of numerical calculations of turbulent-layer dynamics in a stratified fluid that satisfactorily agree with experimental data are presented. The data obtained can be used to estimate the efficiency of mixing within the oceanic depth. 相似文献
14.
V. P. Kukharets O. G. Nalbandyan A. V. Shmakov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(4):411-415
The vertical transport of passive additives in a medium in the presence of both turbulent and convective mixing is studied.
It is shown that, despite the fact that turbulent and convective fluxes are uncorrelated, no additive mechanism of mixing
exists. On the basis of a theoretical model and a comparison with model calculations, it is shown that, in the presence of
both turbulent and convective mixing in a medium, the effect of the interference of turbulent and convective transport mechanisms
takes place. This effect is manifested in the following way: the presence of convection decreases the coefficient of turbulent
transport and the presence of turbulence decreases the coefficient of convective transport; in this case, this effect depends
on the parameter of the inhomogeneity (extension) of convective fluxes. The relative contribution of each of the mechanisms
to the total transport is estimated. It is shown that the interference of turbulence and convection results in an anisotropy
of the coefficient of turbulent transport in an isotropic turbulent velocity field. The effect of the coefficient of molecular
diffusion is assumed to be negligibly small, and its effect is not taken into consideration when analyzing model results.
The interference of the turbulent and convective mechanisms of transport is explained by the inclusion of an additional mechanism
that decreases the distance of linear particle propagation. 相似文献
15.
作者在已完成大气激光雷达系统夜间工作的基础上 ,对白天工作条件下的各种环境背景光的干扰进行了理论与实验分析 ,得出太阳直射光和天空光为白天工作的主要背景干扰。实验结果表明 ,经过激光发射与接收视场角严格匹配及使用干涉滤光器 (2 .6 nm和 0 .15nm)进行窄带滤波 ,背景干扰被明显地剔除 ,可进一步压低背景干扰约 2 0倍。证明采取视场匹配及干涉滤光器的措施可基本保证激光雷达系统在白天条件下工作。 相似文献
16.
17.
近岸多波束测量中的GPS-RTK差分技术及其受影响的因素 总被引：4，自引：0，他引：4
分析了近岸多波束测量中应用GPS-RTK差分技术对船只导航与定位,对在受波浪影响的多波束测量中,船只所受潮汐、换能器吃水的动态变化量等诸影响因素的改正以及船只的运动姿态纠正等问题进行了讨论。使用GPS-RTK系统可以有效地解决潮汐(水位)、波浪影响和换能器吃水的动态变化量对多波束测量精度综合影响的问题,如果使用"一加三"的GPS-RTK接收机,还可以实现船只姿态的高精度综合修正。同时,对4个影响GPS-RTK差分技术系统能力的主要因素应引起重视,采取措施加以解决,使近岸的多波束测量工作更加富有成效。 相似文献
18.
Kyle D. Squires Hidekatsu Yamazaki 《Deep Sea Research Part I: Oceanographic Research Papers》1995,42(11-12)
The effect of small-scale turbulence on marine and aquatic particle transport has traditionally been to act as a means for creating homogeneous distributions. However, previous numerical simulations of heavy particle transport in turbulent flows have shown that particles are preferentially concentrated by turbulence and that effects of preferential concentration are most pronounced for particle parameters comparable to the Kolmogorov scales. Therefore, the focus of the present work is examination of the preferential concentration of marine particles. Application of Kolmogorov scaling indicates that effects of preferential concentration may be important for marine particles with diameters of order 1 mm in the upper mixed layer. Numerical simulations of unstratified isotropic turbulence are then used to support the notion that preferential concentration of particles possessing material characteristics representative of those encountered in marine environments can occur. In the simulations, particles of order 1 mm diameter are idealized as rigid spheres with a density ratio of 1.005. Simulation results demonstrate preferential concentration with peak particle number densities ranging from 10 to 60 times the global mean value. Implications of preferential concentration are also discussed, together with the limitations of the approach employed in the present study. 相似文献
19.
针对当前水深自动选取中水深点与岸线的协调匹配问题,提出了一种与岸线协调的水深自动选取方法。通过分析资料水深点与岸线的平面位置关系,提取出与岸线协调的待选水深点;从航海安全角度考虑,优先选取浅水深点;在此基础上,分别定义水深点与岸线弯曲处、平直处的协调度,并建立协调度评估模型;通过定量计算协调度,选取出与岸线协调匹配的水深点。实验结果表明,所提方法能在岸线弯曲处优先选取出协调的水深点,同时能保证在岸线平直处附近所选取的水深点分布合理;所提方法能够较好地考虑水深点与岸线的图上位置关系,避免水深注记中断岸线、水深注记"上陆"的情况出现。 相似文献
20.
Remote sensing bathymetry inversion can quickly obtain water depth data of large areas, but this process relies on a large number of in-situ depth data points. USV-based (Unmanned Surface Vehicle) technique can obtain the bathymetry data of shallow water where ordinary ships are inaccessible, but this technique is inefficient and generally only data along survey line can be collected. The combination of USV and high-resolution remote sensing provides a new solution for water depth surveying and mapping around an island. This paper focuses on the key techniques, using USV sounding data and GeoEye-1 multispectral remote sensing images covering the region of Wuzhizhou island in the experiment. The results show that the MAE (Mean Absolute Error) of USV sounding is 0.25 m, while the MRE (Mean Relative Error) is 1.41%, and the MRE of remote sensing bathymetry aided by USV sounding can be controlled within 20%. Errors are mainly from areas shallower than 5 m, and are also affected by the USV sounding position accuracy. It shows that it is feasible to combine the USV sounding and high-resolution remote sensing bathymetry, and this technique has broad application prospects in the field of bathymetry in large shallow areas. 相似文献