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41.
海洋激光雷达多次散射回波信号建模与分析 总被引：1，自引：1，他引：0
海洋激光雷达是实现上层海水3维探测的重要工具,激光在海水中的传输伴随着复杂的多次散射效应,建立准确的海洋激光雷达多次散射回波信号模型有助于实现海水光学特性的高精度反演。本文介绍了仿真海洋激光雷达多次散射信号的解析模型、半解析MC(Monte Carlo)仿真方法和传统MC仿真方法,定量对比分析了不同工作条件下3种模型的仿真结果,讨论了工作高度、接收视场角、水质和水体分层等因素对仿真结果的影响。研究表明:3种模型具有高度一致的仿真结果,但在计算效率方面,解析模型优于半解析MC法,半解析MC法优于传统MC法。解析模型优异的计算效率和可靠的计算精度使其在海洋激光雷达辐射传递机理及应用的研究中具有显著优势。 相似文献
42.
Yudi Adityawarman Arata Kaneko Koji Nakano Naokazu Taniguchi Katsuaki Komai Xinyu Guo Noriaki Gohda 《Journal of Oceanography》2011,67(2):173-182
A 30 km-range reciprocal sound transmission experiment was carried out on the line connecting Honshu and Shikoku (the first
and fourth biggest main Japanese islands, respectively) in the central part (Aki-nada) of the Seto Inland Sea, Japan, during
March–May 2010 to measure the mean current and temperature variations over the sea. The range-averaged current along the sound
transmission line was estimated to have a mean and standard deviation of (3.8–4.4) ± (1.7–1.8) cm/s after converting the travel
time difference data into currents, including a fortnightly tidal variation in the range of ±30 cm/s. The positive mean current
implies slow water movement from the west to east through Aki-nada. The range-averaged speed of sound was estimated by converting
from the mean travel time or one-way travel time into the speed of sound, and further converted into temperature for fixed
values of salinity and depth, according to the standard speed of sound formula. Besides the precise measurement (to an accuracy
of 0.01°C) of semidiurnal and diurnal tidal variations and seasonal warming, the temperature data showed periodic variations
with periods of 7.0 and 21.1 days that had never been observed in Aki-nada before. This study suggests that reciprocal sound
transmission is a powerful technique for the long-term accurate measurement of mean current and temperature variations in
coastal and inland seas. 相似文献
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为了研究三维静力适应过程的机理,推导三维静力适应方程组并导出声重力波的频散特征、解析解和能量转换关系以及位涡方程。结果表明,三维静力适应过程实际上就是三维声重力波和重力内波的频散过程,声重力波和重力内波的频率在水平方向上可以区分开来。声重力波的频率随着水平波数和垂直波数的增大而增大。取近轴近似,其解析解在空间上呈螺旋曲面,为大气中热通量和动量从一个区域向另一个区域的输送提供了一种机制,从而为研究大气提供了新的视角。垂直速度在动能与有效势能的转换、有效势能与有效弹性势能的转换中发挥着重要的作用,并且只发生在垂直方向上。在静力适应过程中总能量和位涡是守恒的。适应终态中有效势能比有效弹性势能大一个数量级。 相似文献
45.
在现代全球海洋数值模式的开发研究中,需要在空间尺度为海盆尺度上,时间尺度在几十年、几百年甚至涡流翻转数百次的时间内保持水团属性不变,而湍流混合又是维持层结和海洋环流循环所需要的.在海洋数值模型的开发中,需要将方程组在全球网格上进行离散处理,这势必会产生截断误差,从而产生虚假越中性层混合.因此将目前国内外学者和研究人员对虚假混合的来源、诊断方法、控制方法整理做出简要综述,以供读者参考学习. 相似文献
46.
In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean(Model for Prediction Across Scales) using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z* vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy(RPE), front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter χ, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number(HGRN), Re?, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al.(2012), i.e., MITGCM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MITGCM and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexagon cell and the quadrilateral cell with the same resolution. Both the Zalesak(1979) flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy. 相似文献
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使用"递减平均法"和渤海28个石油、平台、浮标站资料分析得到的渤海10m风速逐时格点场,对ROAD模式(Regional Ocean and Atmosphere Model)渤海区域10m风速预报进行误差订正,不同权重系数试验表明:对于渤海10m风速预报场,权重系数取0.18,订正效果最佳,12～72h预报时效内,月逐时均方根误差和平均偏差均有明显改善,分别减小1.0～1.5m/s和2.3～3.0m/s;对比渤海北部、西部和中部代表格点72h预报时效内,逐12h最大风速评分结果发现:60h预报时效内,当风速预报在5～6级时,渤海北部、中部和西部订正后的预报评分大多有所提高;当风速预报在7级时,渤海北部和中部分别在36～72h和24～48h,预报评分有提高;在实况出现最多的风力分布范围内评分提高最多。 相似文献
49.
在线性斜压原始方程组的基础上，从频率和群速方面讨论了由水平网格 (C、Z网格) 和垂直网格 (L、CP、LZ、LY网格) 组合而成的几种三维网格 (C/L、C/CP、Z/LZ、Z/LY) 的计算频散性并分析了各种网格出现偏差的原因，结果表明三维网格C/CP (水平网格为C网格垂直网格为Charney-Phillips网格) 与Z/LZ（水平网格为Z网格垂直网格为LZ网格）计算频散性能较好。从而为原始方程大气模式选取三维网格提供指导。 相似文献
50.
Yudi Liu 《Computational Geosciences》2008,12(2):245-253
Starting from nonhydrostatic Boussinesq approximation equations, a general method is introduced to deduce the dispersion relationships.
A comparative investigation is performed on inertia-gravity wave with horizontal lengths of 100, 10 and 1 km. These are examined
using the second-order central difference scheme and the fourth-order compact difference scheme on vertical grids that are
currently available from the perspectives of frequency, horizontal and vertical component of group velocity. These findings
are compared to analytical solutions. The obtained results suggest that whether for the second-order central difference scheme
or for the fourth-order compact difference scheme, Charny–Phillips and Lorenz (L) grids are suitable for studying waves at
the above-mentioned horizontal scales; the Lorenz time-staggered and Charny–Phillips time staggered (CPTS) grids are applicable
only to the horizontal scales of less than 10 km, and N grid (unstaggered grid) is unsuitable for simulating waves at any
horizontal scale. Furthermore, by using fourth-order compact difference scheme with higher difference precision, the errors
of frequency and group velocity in horizontal and vertical directions produced on all vertical grids in describing the waves
with horizontal lengths of 1, 10 and 100 km cannot inevitably be decreased. So in developing a numerical model, the higher-order
finite difference scheme, like fourth-order compact difference scheme, should be avoided as much as possible, typically on
L and CPTS grids, since it will not only take many efforts to design program but also make the calculated group velocity in
horizontal and vertical directions even worse in accuracy. 相似文献