组合型水光仪器的阴影和姿态对水光测量的影响

本文用后向Ｍｏｎｔｅ－Ｃａｒｌｏ方法模拟了有水光测量仪器存在的水体中的光场,计算了在Ｌｕ和Ｅｕ测量时仪器阴影误差与仪器在水平面内旋转角的关系,仪器倾斜时的辐亮度阴影误差与倾斜角的关系和阴影误差与深度的关系。高精度的水光测量在测量过程中和处理数据时应该解决好这个问题。     

MODIS辅助的北京一号卫星影像近海Ⅱ类水体大气校正

利用空间分辨率为500 m的MODIS 1B数据及有关MODIS数据产品计算其近红外波段的气溶胶辐亮度,由此外推北京一号卫星多光谱影像各波段的气溶胶辐亮度,以实现对该影像的大气校正,取得了良好的效果.该方法克服了传统大气校正方法依赖于现场测量大气参数的缺陷,拓展了非水色传感器在水体监测领域的应用前景.     

水下光谱辐射计光学特性的测试与分析

为适应高精度水下光学测量的需求，设计研制了多通道水下光谱辐射计。该辐射计可同步测量12波段的下行／上行光谱辐照度和7波段的上行光谱辐亮度。对该辐射计的主要性能指标，如余弦响应特性、浸没因子、光谱辐射精度、稳定性和重复性进行了室内测试和分析，用MonteCarlo方法模拟了阴影误差，给出并分析了现场实验数据及部分推导的物理量。结果表明，该光谱辐射计各波段的中心波长和带宽偏差小于1．6nm，稳定性优于5％，阴影误差可控制在5％之内，具有良好的余弦响应特性，满足当前定量化水色遥感现象光辐射测量的技术要求。     

由TSRB辐射计数据估算海面离水辐亮度的经验方法

为建立基于经验统计的TSRB辐射计数据估算离水辐亮度的方法,利用SeaBASS数据库中640多个现场测量的辐亮度和辐照度光谱剖面数据,建立向上辐亮度衰减系数K_(lu)的经验算法.此算法为幂指数形式,输入变量为水下0.65 m的向上辐亮度(490 nm)与海面上向下的辐照度(555 nm或665 nm)之比(即为TSRB直接测量的两个参数).当水体较清时,输入为蓝绿波段之比,当水混浊时,采用蓝红波段之比.获得了K_(lu)后,海面以上的辐亮度(离水辐亮度)由z=0.65 m处的辐亮度外推获得.初步的检验结果表明,该方法对一类和二类水域都有很好性能,且算法实现简单,运行速度快.     

锚泊光学浮标浮体设计及近海试验

文中设计的光学浮标采用了柱状浮体, 提出了自由旋转的马鞍链结构。理论计算结果表明, 该光学浮标一是初稳性高度大, 二是光学浮标重心位于浮心之下, 浮标的摇摆角较小, 抗倾斜及倾覆能力强。海上试验结果表 明, 对于风力7节、浪高3—4m以下的海况, 浮标倾角≤5°的次数占总采样次数的 54%, 浮标倾角≤10°的次数占总采样次数的83%, 浮标性能较好地满足了水下光辐射测量的技术要求。为减小阴影效应带来的光辐射测量误差, 文中采用了两种解决方法: 一是伸臂结构解决浮标体阴影的影响, 当太阳天顶角为0°时, 在近岸或者清洁水体中浮标体阴影引起的向上辐亮度测量误差分别不大于4% 和1%; 二是光纤光谱仪测量技术减少仪器自阴影的影响, 设计的光谱辐照度和辐亮度光学探头直径均为0.042m, 当水体光束衰减系数为0.12m-1, 太阳天顶角为10°时, 自阴影引起的向上辐亮度测量误差仅为1.5%。     

基于S2000光谱仪的小型海面高光谱辐射计的研制

将普通的小巧型S2000光谱仪组装改造成用于海面测量的高光谱辐射计,安装在船只等移动平台上进行原位测量,可以获得向下辐照度和向上辐亮度的实验数据.阐述了整体设计思路,说明了其光路结构,光学采集单元分为光谱辐照度光学探头和光谱辐亮度光学探头.叙述了通过机械结构的调整来更准确地测量离水辐亮度,并给出了基于计算机进行显示和存储的编程软件.此系统获得的试验测量结果可以为海洋学研究提供充分的现场光学数据,有一定的实用价值.     

海面光谱辐射计系统研制及遥感反射比的测量

本文报道海面光谱辐射计的研制、定标和海上现场实验测量。运用一个 2 5 6元光电二极管列阵传感器件测量海面离水辐亮度和向下辐照度的光谱分布 ,可计算得出遥感反射比。该仪器所测量的数据可以用于海洋方面相关专业的科学研究 ,并给出海上实验测量数据     

海面之上法中海面反射率和观测几何模拟研究

测量离水辐亮度的水面之上测量方法中最大的不确定性因素是太阳耀斑的污染和海面反射率的估算。文章根据Cox和Munk研究结果,利用大量随机数模拟海面波浪倾斜,估算不同仪器观测方向与风矢量几何以及不同仪器视场角下的海面反射率,并估算出不同太阳天顶角及相对风矢量方位角的太阳耀斑基本分布。     

机载海洋激光雷达测量叶绿素a浓度、悬移质浓度和浅海深度的性能估计

以14:00时离水辐亮度作为背景光强度,模拟355nm激光雷达测量不同深度水层叶绿素a荧光的信噪比.分析体积衰减系数c、辐照度衰减系数k、散射系数b和透明度盘深度(SDD)的关系.最后模拟532nm激光雷达测量悬移质浓度的最大测量深度和误判率小于10%时的最大海底探测深度随SDD的变化.     

船基系统海气通量测量方法研究

海气通量交换是海洋学和气象学许多领域共同研究的内容,是气候形成和变化的重要机制之一。文章通过比较测量海气通量的几种方法,提出了在船基仪器上使用直接协方差法测量海气通量的方法,并给出了船体运动造成测量结果误差的校正算法。     

Atmospheric correction of SeaWiFS imagery for turbid coastal and inland waters

A practical algorithm of atmospheric correction for turbid coastal and inland waters is provided. The present algorithm uses the property that the water-leaving radiance at 412 nm increases very tittle with the increasing of water turbidity. Thus, in very turbid coastal and inland waters, the radiance at 412 nm can be used to estimate the aerosol scattering radiance at 865 nm. The performance of the new algorithm is validated with simulation for several cases. It is found that the retrieved remotely sensed reflectance is usually with error less than 10% for the first six bands of SeaWiFS. This new algorithm is also tested under various atmospheric conditions in the Changjiang River Estuary and the Hangzhou Bay where the sediment concentration is very high and the standard SeaWiFS atmospheric correction algorithm creates a mask due to atmospheric correction failure. The result proves the efficiency of this simple algorithm in reducing the errors of the water-leaving radiance retrieving using SeaWiFS satellite data.     

A general purpose exact Rayleigh scattering look-up table for ocean color remote sensing

1 Introduction In the total radiance received by an ocean color remote sensor, over 80% radiance is the contribution being scattered by air molecule and aerosol, and a wa- ter-leaving radiance carrying the ocean color informa- tion is only a small part. T…     

通用型海洋水色遥感精确瑞利散射查找表

当前对海洋水色遥感精确瑞利散射的计算均采用查找表方式进行,但由于这些查找表是针对特定遥感器生成的,无法直接应用于新的水色遥感器,给实际应用带来一定程度的麻烦,为此提出了一种通用的海洋水色遥感精确瑞利散射查找表.首先,详细地推导了加倍法解大气矢量辐射传输方程的基本关系式和实际的计算原理.通过与MODIS精确瑞利散射查找表计算结果比较,证明利用加倍法计算瑞利散射的精度优于0.25%,完全能够满足当前海洋水色遥感大气校正对瑞利散射计算精度的要求,并可以用来生成精确瑞利散射查找表.其次,利用加倍法解大气矢量辐射传输方程,生成了一个通用的海洋水色遥感精确瑞利散射查找表,验证结果表明该查找表可用于所有水色遥感器的精确瑞利散射计算,且计算精度优于0.5%.     

Accuracy estimation of loading correction in gravity observation

To estimate the loading correction, the convolution integral of tidal height with gravity Green's function is usually adopted. Therefore, two kinds of error sources should be discussed, i.e. errors produced by different earth models and errors due to the inaccuracy of the cotidal maps. Thus, the effect of different earth models on tidal correction was estimated by using different loading Love numbers and gravity Green function obtained on the basis of two different earth models, G-B and 1066 model. We also calculated the error caused by Schwidersky's cotidal map, by assuming the error of average tidal height to be 5 cm in 1°×1° grids, but yet the effect coming from the errors of local cotidal maps had not been taken into consideration in this work. In carrying out this calculation, the results of tidal height errors in adjacent ocean around station, harmonic coefficient errors in open ocean and a truncation error are discussed respectively.     

FY-3D卫星MWHS-2辐射率资料直接同化对台风“米娜”预报的影响*

文章基于天气研究和预报(weather research and forecasting, WRF)模式中的FY-3D卫星微波湿度计Ⅱ(micro-wave humidity sounder 2, MWHS-2)辐射率资料的直接同化模块, 采用三维变分(three dimensional variation, 3DVar)方法在晴空条件下同化MWHS-2辐射率资料, 考察MWHS-2辐射率资料同化对台风“米娜”(2019)预报的影响。文中设计了4组试验, 第一组试验不同化任何资料, 第二组试验同化了单独的全球通信系统(global telecommunications system, GTS)常规资料, 第三组试验联合同化了GTS常规资料和MWHS-2辐射率资料, 第四组试验将MWHS-2辐射率资料换成先进技术微波探测计(advanced technology microwave sounder, ATMS)辐射率资料同化。研究结果表明: 偏差订正后各通道观测和背景场差值的均值趋于0, 同化后分析场相对观测的标准差与均方根误差较背景场显著减小, 同化过程是有效的。与仅同化GTS常规资料和同化ATMS资料的试验相比, 同化晴空MWHS-2辐射率资料后的增量场在台风中心附近有负的高度增量和正的温度增量, 从动力与热力上有助于台风的维持。在确定性预报最后的12h, 同化晴空MWHS-2辐射率资料的试验能够改进500hPa环流形势的模拟, 加强西南方向引导气流的强度, 从而最终减小台风路径预报的误差。     

新一代静止气象卫星葵花8号的晴空红外辐射率资料同化对台风“天鸽”的预报影响研究

本文以2017年第13号台风“天鸽”（Hato）为例,在WRFDA同化系统中结合日本葵花8号（Himawari-8）资料,通过同化Himawari-8晴空红外辐射率资料并进一步考察其对台风“天鸽”的结构、强度、路径分析和预报的影响。研究结果表明:同化Himawari-8晴空红外辐射率资料对台风背景场的水汽相关变量分析有显著改进,对背景场中的台风水汽信息有一定的改进作用。与控制实验,即没有同化Himawari-8晴空红外辐射率资料的实验相比,加入同化实验对台风“天鸽”的风场、500 hPa气压场的分析效果有所提高,台风气旋性环流加强,并进一步改进了对台风“天鸽”的路径、台风中心最低气压和近中心最大风速的预报。平均路径误差和降水预报相对于常规观测变量的均方根误差均有所改善。     

A simulation involving MAPS video bandwidth reduction, acoustic channel errors, and error checking

The reliable acoustic transmission of images that have been processed by a video bandwidth reduction technique such as Micro-Adaptive Picture Sequencing (MAPS) necessitates a robust coding scheme. This is due to the fact that errors effect compressed data more seriously than uncompressed data. For this reason image quality is a function of three system variables: image compression, channel noise, and error checking. A real-time simulation has been developed to determine the relationship between the three system variables. The simulator uses two 68000 microcomputers connected by a serial link; one does image compression and noise modeling while the other performs error checking and image reconstruction. The noise model uses 17 characteristics and operating parameters of the acoustic channel to corrupt the image data with single bit random errors. At the receiver the error checking can correct up to 90 percent of the most serious single bit errors.     

海洋地磁测量资料的虚拟检查线调差方法

在海洋磁力测量中,因受测量环境及各项改正的残余量等因素的系统性影响,不同测线间存在着不同程度的系统差,这种测线系统差会使测区磁场水平不统一,导致磁异常等值线图失真。为此,研究了基于虚拟检查线的海洋地磁测量数据调差方法,该方法尝试在不使用检查线数据情况下,沿垂直于测线方向选取一定数量的虚拟检查线,根据测线数据拟合出各条虚拟检查线上场的分布规律,并将测线方向拟合前后残差的平均值作为各条测线上的测线系统差,对各条测线数据进行改正。仿真计算与分析表明:对于磁异常变化较平缓的测区,该方法可以有效消除测线系统差;当磁异常变化剧烈时,该方法可以部分消除测线系统差。     

Indication of bottom transport in shallow marine regions based on the data of satellite ocean color scanners

By example of a testing area in the northern Caspian Sea, a case study has been conducted to examine the feasibility of indication of near-bottom water transport from the data of ocean color scanners (OCS) for the basins whose bottom is shallower than the lower limit of the water-leaving radiance origination layer. The testing area has provided the desirable diversity of radiance origination conditions owing to an isolated underwater ridge. Based on the archived materials of the OCS SeaWiFS for 2000–2004, statistics of spectral normalized water-leaving radiances of the testing area have been computed. Hypothetically, the displacements of a radiance maximum in reference to the ridge were due to different mechanisms of interaction of water motions with bottom relief and bottom sediments. The correspondence between the patterns of radiance maximum displacements and the current notions of general water transport in the vicinity of the testing area has been established. Hopefully, the archived data of OCSs can be useful for revealing the patterns of seasonal and interannual variability of the near-bottom water transport at shallows with favorable bottom properties.