The SeaSat-A satellite scatterometer

This paper describes the methods used to develop performance requirements and design characteristics for the microwave scatterometer (SASS) ocean-surface wind sensor on the NASA SeaSat-A satellite. Wind vector measurement requirements from the SeaSat user community such as wind speed and direction accuracy, resolution cell size, grid spacing, and swath width formed the basis for defining instrument characteristics. The resulting scatterometer is designed for 14.6 GHz using four fan beam antennas to measure wind speed and direction over a 1000-km swath width with a resolution cell size50 times 50km. Results presented show scatterometer accuracy satisfies user requirements for wind speed from 4 m/s to greater than 24 m/s for the nominal SeaSat-A orbit of 790 km altitude,108deginclination, and 0.001 eccentricity.     

Seasat-A satellite scatterometer instrument evaluation

The Seasat-A satellite scatterometer (SASS) was designed to measure ocean surface wind speed and direction in twenty-four (24) independent cells over a 1000-km swath. It operated in the interrupted CW mode at a frequency of 14.6 GHz with four (4) fan beam antennas and used Doppler filtering in the receiver for resolving the cells on the surface. The instrument began operating in space on July 6, 1978, and gathered normalized radar cross section (sigma^{0}) data for approximately 2290 h. The purpose of this paper is to describe the in-orbit evaluation of the SASS hardware and its compatibility with the spacecraft. It has been determined that the scatterometer operated flawlessly throughout the mission, met all design requirements, and established a good data base for geophysical processing.     

中法海洋卫星散射计近海岸海面风场反演研究

中法海洋卫星散射计(CSCAT)使用扇形波束旋转扫描体制,能够以多角度测量同一海面的雷达后向散射系数,并具有空间分辨率较高的特点。这为近海岸海面风场反演提供了新的机遇。本文介绍了CSCAT近海岸海面风场处理的主要流程和关键技术。特别地,在风场反演之前,利用一种矩形窗算术平均的方法将L1B级的高分辨率条带数据组合平均到相应的风矢量单元中,从而实现近海岸风场反演的快速预处理。通过对比CSCAT、欧洲先进散射计(ASCAT)以及美国QuikSCAT的近海岸风场,发现CSCAT风场的质量在离岸40 km以外区域具有良好的一致性,而在离岸40 km以内显著恶化。分析表明,CSCAT近海岸区域风场统计特征恶化的原因可能是由潜在的海冰污染引起的。总体而言,CSCAT的近海岸风场与模式背景风场和浮标风场都具有良好的一致性。     

基于变分多参数正则化方法融合卫星散射计资料

基于常规三维变分同化（3DVAR）思想和反问题中的正则化技术,提出了适用于风场融合的带正则化约束项的3DVAR方法,在南海海域开展数据融合试验,同时采用模型函数方法确定合理的正则化参数,针对一次台风个例进行了QuikSCAT散射计海面风场数据和华南中尺度模式海面风场数据的融合试验,结果表明采用带正则化约束的3DVAR融合方法,明显消除了常规3DVAR方法融合风场时带来的虚假信息,融合后分析风场以及涡度场和散度场分布均匀,结构清晰,气旋中心显著,且分析场中观测起主导作用;采用信号自由度（DFS）方法对融合方法进行定量评估,发现相对常规3DVAR方法,带正则化约束的3DVAR融合系统中观测数据提供的DFS较多,同时提高了观测场对分析场的影响;基于独立观测资料对融合结果进行检验发现相对华南中尺度模式和常规3DVAR方法的统计结果,带正则化约束的3DVAR方法得到的风场具有最小的均方根误差和最大的相关系数。     

基于散射计风场数据的台风强度诊断方法——以海洋二号卫星数据为例

本文提出了一种基于散射计风场数据的台风定强方法。该方法定义了台风所在海区的一个圆形区域上的风速平均值来对台风进行定强,并使用海洋二号卫星散射计历史数据对该方法进行了验证。验证结果表明,该台风定强方法可以克服散射计反演台风风速过低的问题。与台风强度监测的历史记录比较的结果显示,在台风强度低于"强台风"这一强度等级时,该方法能够有效估算台风强度。     

Validation and accuracy analysis of wind products from scatterometer onboard the HY-2B satellite

The Chinese marine dynamic environment satellite HY-2B was launched in October 2018 and carries a Ku-band scatterometer. This paper focuses on the accuracies of HY-2B scatterometer wind data during the period from November 2018 to May 2021. The HY-2B wind data are validated against global moored buoys operated by the U.S. National Data Buoy Center and Tropical Atmosphere Ocean, numerical model data by the National Centers for Environmental Prediction, and the Advanced Scatterometer data issued b...     

A study of a new retrieval algorithm for measurement of oceanic windvectors field using satellite microwave scatterometer

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“海洋1号”卫星在海冰监测和预报中的应用

“海洋1号A”卫星是我国发射的第一颗海洋卫星.2002~2003年冬季,该卫星首次应用于我国渤海海冰监测和预报.建立了从卫星1B级数据开始的海冰反演系统,提供海冰遥感图像和海冰密集度、冰厚与冰外缘线数值产品,作为渤海海冰监测和海冰数值预报初始场的重要信息来源,以及海冰预报质量检验的参考依据之一.介绍所发展的“海洋1号A”卫星海冰反演系统的流程、算法和反演参数,海冰反演结果,及其在渤海海冰监测和预报中的应用.     

“HY—1A”卫星海洋水色扫描仪像旋转图像校正处理

"海洋1"号("HY—1A")卫星海洋水色扫描仪由于K镜的失效而出现了像旋现象,对获得的卫星图像质量产生直接影响。基于光学反射矢量理论,分析了多元探测器并行扫描方式下45°扫描镜加K镜的扫描轨迹特征,利用图像之间的相关性,首先自动寻找K镜停转的准确角度,然后根据K镜的停转角度与多元并扫理论对像旋图像进行了校正处理,获得了可用的校正图像。     

大气对微波散射计回波信号衰减的修正方法研究

为了使微波散射计测得的海面后向散射具有足够的精度，必须考虑大气对微波衰减的影响。大气对微波的衰减可以用微波射计来测定。本文将估算晴空、云和降雨天气下的衰减系，讨论计算海面发射率及用微波辐射计剩余亮温估算散射计工作频率下大气衰减的方法。     

A two-frequency hydroacoustic scatterometer for bubble scatteringinvestigations

High-frequency bubble layer scattering investigations require the measurement of the intensity of backscattered sound and the corresponding depth of the scatterers below the moving surface. Especially at high sea state conditions and high acoustic frequencies, bubbles acoustically mask the surface, i.e., the surface return cannot be detected. However, this environmental condition is the most interesting one in bubble scattering investigations and a reliable method is required to determine the range of the scatterers to the surface displacement. A method for the determination of the vertical profiling of acoustic scattering in the presence of bubbles at high sea state conditions is presented. It is based on the transmission of a low-frequency signal alternately to the high-frequency signal at which the scattering investigations are performed. The only information that is extracted from the low-frequency echo is the onset of the surface return. It is used to compute the true depth of scatterers at the high frequency. Experiments were conducted to determine the optimum low frequency at which the detection of the surface onset in the presence of a high bubble concentration is ensured. A screening ratio is defined to give a measure of the acoustic masking of the sea surface. It is depicted for an extreme wind condition (20 m/s) for the frequency range of 5-25 kHz and as a function of wind speed for 50 kHz measurements. Selected results of subsurface bubble scattering at 50 kHz from experiments under open sea conditions are presented for the wind speed regime from 9 to 22 m/s. Additionally, the two-frequency scatterometer is used to measure sea state characteristics simultaneously to the scattering investigations by remote sensing techniques     

大气对频率为14.59GHz微波散射计信号衰减的计算

本文利用Ｓｅａｓａｔ－Ａ卫星辐射计实测的大气中的水气含量、云中液态水含量及降雨强度等参数计算大气对微波的衰减，从而实现对１４．５９ＧＨｚ微波散射计衰减进行补偿之目的。     

"三步法"静校正在鄂北麻黄山地区地震资料处理中的应用

针对麻黄山黄土塬地区塬、梁、卯、坡等复杂地表条件,结合各处理系统的优点,采用“三步法”静校正技术解决该地区由于静校正不准所引起的假构造、串相位等现象。“三步法”静校正技术的应用,进一步提高了静校正精度,保证了地震资料解释结果的可靠性。     

散射计风反演算法的数值模拟研究

由于缺乏散射计的σ°资料及相应的海面风数据，本文采用数值模拟方法对反演算法及多解消除步骤进行了初步的研究。结果表明，对于NSCAT散射计的设计参数，采用常用的反演算法进行模拟，约有70％的第一解是真实解。经过平滑处理之后约有95％反演解达到了散射计的设计精度，即风速误差＜2m／s或10％（取大者），风向误差＜20°。     

“HY-1”卫星COCTS水色遥感器精确瑞利散射算法研究

“HY-1”卫星是我国自主研制发射的第一颗海洋卫星,水色遥感器COCTS具有8个可见光(412,443,490,520,565,670 nm)、近红外通道(750,865 nm)以及2个热红外通道(10.30~11.40,11.40~12.50μm).COCTS遥感器上采用了多元并扫技术用以提高遥感器的信噪比和探测灵敏度,但是由于并扫会带来像元旋转的问题,于是我国“HY-1”卫星水色遥感器COCTS上采用了K镜消旋技术,而K镜消旋技术带来的一个消极影响是偏振响应很大,通过发射前实验室监测结果发现其值达到了8%.     

卫星散射计与海面平台所测的风场数据比较

基于南海北部海面PY30-1石油平台气象站测风仪2011年7月19日—2012年9月17日实测的风场数据,分别开展了对卫星搭载的ASCAT和HY-2散射计所测风场数据的比较研究,分析散射计的测风能力(选取的时空窗口为30 min和25 km)。结果表明:在南海北部海域,ASCAT 散射计所测风速和PY30-1石油平台气象站观测风速的均方根误差为2.53 m/s,风向偏差较大,均方根误差为47.87°;HY-2散射计所测风速和PY30-1石油平台气象站观测风速的均方根误差为3.41 m/s,风向的均方根误差为58.66°。分别按低、中和高风速的不同条件将ASCAT和HY-2散射计所测的风场数据与PY30-1石油平台气象站观测的风场数据加以比较可知,ASCAT和HY-2散射计都具有较好的测风能力, 前者所测风速与PY30-1石油平台气象站测风仪观测风速的均方根误差稍小于后者。在150 min和15 km的时空窗口下,ASCAT与HY-2散射计所测风速的均方根误差为0.72 m/s,风向的均方根误差为8.50°。     

A three-frequency scatterometer technique for the measurement ofocean wave spectra

A microwave technique for the measurement of ocean wave spectra has been compared with wave gauge output during extensive field testing. The method is based on the dual-frequency technique for detecting long ocean waves by matching the modulation of short waves with the beat wavelength between two transmitted microwave frequencies. The new method, however, utilizes three microwave frequencies in order to reduce mean backscatter not related to short-wave modulation. Two prototype scatterometers have been built using three frequencies at L-band and at K_u-band. Wave spectra have been measured by both radar systems which, when properly normalized, agree well with simultaneous in situ measurements taken by conventional wave gauges at the pier site. Thirteen sets of spectra have been computed, five of which correspond to a situation in which a local wind sea was generated and then decayed. The present experiment does not demonstrate the directionality of this new technique     

The accuracy of GOES satellite clocks

Clocks that receive and decode time signals from the GOES satellites are commonly used to provide accurate time reference for the recording of a wide variety of data types in academic research. These satellite clocks must be used with adequate knowledge of their operation. When corrections for satellite position are not made, comparison data presented in this paper show that errors of up to several milliseconds will result. However, with care and the application of proper corrections it is shown that accuracies of 100 to 200 microseconds are achievable.     

HY-2B卫星散射计海面风场产品质量分析 *

星载微波散射计是获取全球海面风场信息的主要手段, HY-2B卫星散射计的成功发射为全球海面风场数据获取的持续性提供了重要保障。本文利用欧洲中期天气预报中心(European Center for Medium-Range Weather Forecasts, ECMWF)再分析风场数据、热带大气海洋观测计划(Tropical Atmosphere Ocean Array, TAO)和美国国家数据浮标中心(National Data Buoy Center, NDBC)浮标获取的海面风矢量实测数据, 对HY-2B散射计海面风场数据产品的质量进行统计分析。分析表明, HY-2B风场与ECMWF再分析风场对比, 在4~24m·s^-1风速区间内, 风速和风向均方根误差(root mean square error, RMSE)分别为1.58m·s^-1和15.34°; 与位于开阔海域的TAO浮标数据对比, 风速、风向RMSE分别为1.03m·s^-1和14.98°, 可见HY-2B风场能较好地满足业务化应用的精度要求(风速优于2m·s^-1, 风向优于20°)。与主要位于近海海域的NDBC浮标对比, HY-2B风场的风速、风向RMSE分别为1.60m·s^-1和19.14°, 说明HY-2B散射计同时具备了对近海海域风场的良好观测能力。本文还发现HY-2B风场质量会随风速、地面交轨位置等变化, 为用户更好地使用HY-2B风场产品提供参考。