基于微波散射实验的油种识别研究     

马靖  过杰 《海洋与湖沼》2023,54(1):30-43

海上溢油来源复杂,溢油种类多样,正确识别溢油类型对于溢油应急的快速反应具有重要意义。合成孔径雷达(synthetic aperture radar,SAR)具有全天时全天候的监测优势,在海面溢油监测中发挥着主力军作用,但在油种识别方面存在不足。利用C波段全极化散射计对柴油、原油、油水混合物和棕榈油进行外场实验观测,探究微波识别油膜的敏感特征参数,并将敏感特征参数应用于海上油膜实验获取的SAR图像进行油种识别。结果表明,在垂直(vertical transmission vertical reception,VV)极化方式下的油水差(?σ⁰)可以有效识别植物油和矿物油;基于d B和linear units表达的后向散射系数(NRCS)计算的抑制比(DR)在垂直(VV)和水平(horizontal transmission horizontal reception,HH)极化方式下可以有效识别植物油和矿物油,并且在交叉(vertical transmission horizontal reception/horizontal transmission vertical...  相似文献   

Evaluation of Vector Winds Observed by NSCAT in the Seas around Japan     

Harunobu Masuko  Kohei Arai  Naoto Ebuchi  Masanori Konda  Masahisa Kubota  Kunio Kutsuwada  Teruko Manabe  Akira Mukaida  Tetsuo Nakazawa  Atsushi Nomura  Akira Shibata  Yoshihiko Tahara 《Journal of Oceanography》2000,56(5):495-505

In order to validate wind vectors derived from the NASA Scatterometer (NSCAT), two NSCAT wind products of different spatial resolutions are compared with observations by buoys and research vessels in the seas around Japan. In general, the NSCAT winds agree well with the wind data from the buoys and vessels. It is shown that the root-mean-square (rms) difference between NSCAT-derived wind speeds and the buoy observations is 1.7 ms^–1, which satisfies the mission requirement of accuracy, 2 ms^–1. However, the rms difference of wind directions is slightly larger than the mission requirement, 20°. This result does not agree with those of previous studies on validation of the NSCAT-derived wind vectors using buoy observations, and is considered to be due to differences in the buoy observation systems. It is also shown that there are no significant systematic trends of the NSCAT wind speed and direction depending on the wind speed and incidence angle. Comparison with ship winds shows that the NSCAT wind speeds are lower than those observed by the research vessels by about 0.7 ms^–1 and this bias is twice as large for data observed by moving ships than by stationary ships. This result suggests that the ship winds may be influenced by errors caused by ship's motion, such as pitching and rolling.  相似文献   

An improved QuikSCAT wind retrieval algorithm and eye locating for typhoon     

ZHONG Jian  FEI Jianfang  HUANG Sixun  DU Huadong  ZHANG Liang 《海洋学报(英文版)》2012,31(1):41-50

This paper proposes a rain considered geophysical model function (GMF), to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency (JMA). The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section (NRCS) is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective.  相似文献   

岸基C波段和X波段雷达观测海面后向散射系数   总被引：1，自引：0，他引：1  

洪鹰  孙瀛  罗邦煦  白桂欣  郑淑卿 《台湾海峡》1995,14(2):187-194

本文给出了1992年4月中旬在浙江宁波北仑港进行的岸基X波段及C波段观测海面雷达后向散射系数σ°现场实验的部分结果，并对σ°、入射角θ、风速U及相对方位角X的关系作了讨论。实验表明，当风速在2．2～11．5m／s时，对于HH、VV及HV极化：（1）当20°≤θ＜65°时，对于X波段和C波段，σ°和exp（θ／θ。）成正比，且θ。在5°～8°之间；（2）对于X波段，当θ≤65°时。σ°比于Ur，在45°入射角VV极化时，r＝1．49；（3）σ°在逆风时接近最大，在侧风时接近最小。  相似文献   

大气对频率为14.59GHz微波散射计信号衰减的计算     

郑淑卿  林明森 《台湾海峡》1997,16(2):186-194

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。  相似文献   

SeaWinds散射计海面风场神经网络建模研究   总被引：2，自引：0，他引：2  

解学通  方裕  陈克海  黄舟  陈斌 《地理与地理信息科学》2007,23(2):12-17

根据Sea Winds散射计只有两个入射角和两种极化方式的特点,利用其L2A数据和F291海上浮标数据,针对传统建模方法的不足和限制,借助神经网络建立了一个两种极化方式下统一的神经网络地球物理模型函数。该模型的主要特点是建模风矢量全部取自海上浮标测量数据,因而所用风矢量更加客观准确。通过与Qscat-1模型的比较和L2B与浮标风速之间的偏差统计分析,证明了该神经网络模型的有效性,并发现Qscat-1模型存在一定的系统性偏差。  相似文献   

Indian Ocean surface winds from NCMRWF analysis as compared to QuikSCAT and moored buoy winds     

B. N. Goswami  E. N. Rajagopal 《Journal of Earth System Science》2003,112(1):61-77

The quality of the surface wind analysis at the National Centre for Medium Range Weather Forecasts (NCMRWF), New Delhi over the tropical Indian Ocean and its improvement in 2001 are examined by comparing it within situ buoy measurements and satellite derived surface winds from NASA QuikSCAT satellite (QSCT) during 1999, 2000 and 2001. The NCMRWF surface winds suffered from easterly bias of 1.0–1.5 ms^-1 in the equatorial Indian Ocean (IO) and northerly bias of 2.0–3.0 ms^-1 in the south equatorial IO during 1999 and 2000 compared to QSCT winds. The amplitude of daily variability was also underestimated compared to that in QSCT. In particular, the amplitude of daily variability of NCMRWF winds in the eastern equatorial IO was only about 60% of that of QSCT during 1999 and 2000. The NCMRWF surface winds during 2001 have significantly improved with the bias of the mean analyzed winds considerably reduced everywhere bringing it to within 0.5 ms^-1 of QSCT winds in the equatorial IO. The amplitude and phase of daily and intraseasonal variability are very close to that in QSCT almost everywhere during 2001. It is shown that the weakness in the surface wind analysis during 1999 and 2000 and its improvement in 2001 are related to the weakness in simulation of precipitation by the forecast model in the equatorial IO and its improvement in 2001.  相似文献   

广义高斯模型阈值的南极冰盖冻融探测     

王星东  王成  李新广 《冰川冻土》2015,37(4):940-945

在微波散射计的简单冰盖融化物理模型的基础上, 提出了不依赖于实地观测数据的自动阈值分割的南极冰盖冻融探测的新算法, 即利用广义高斯模型对通过微波散射计简单冰盖融化物理模型变换得到的数据做直方图统计, 得到干湿雪划分的最优阈值, 从而得到干湿雪的冻融分布图. 这种算法不但解决了物理模型算法需依赖实测冰盖融化信息才能进行冰盖冻融探测的问题, 而且能自动选择较多的样本, 提高了冰盖冻融探测的计算效率、 实用性和可操作性. 算法也能被应用到其他地区, 为全球的冰盖冻融探测提供了方法学的支持和补充.  相似文献   

一种改进的扇形波束旋转扫描散射计海面风矢量反演算法     

解学通  文雅  黄舟 《海洋学报(英文版)》2017,36(5):83-89

扇形波束旋转扫描散射计（RFSCAT）是约十年前才被提出来的一种新型星载微波散射计。与其它旋转扫描散射计类似,其星下点附近区域和刈幅边缘区域的风场反演误差相对较大。在本文设定的参数条件下,RFSCAT散射计刈幅边缘区域的风向反演精度相对于轨道中间区域降低了约9°。针对这一问题,本文为RFSCAT散射计提出了一种改进的风矢量反演算法。新算法的主要特征是,根据风向反演偏差直方图,在整个刈幅区域内,对模糊解风向取值区间进行自适应扩展,以获取并保留更多可能风向解。利用模拟的100条轨道的L2A数据,对新算法进行反演验证。实验结果证明,新算法能够有效改善RFSCAT散射计星下点附近区域和轨道刈幅边缘区域的风向反演精度。星下点和刈幅边缘上的风矢量单元的风向反演精度相对于标准的MLE算法分别提高了1.6°和9°。  相似文献   

海洋目标的HY-2A卫星微波散射计在轨辐射定标研究     

穆博  宋清涛 《遥感学报》2014,18(5):1072-1086

HY-2A卫星微波散射计主要用于测量海表面的风速和风向,为了满足其风速和风向的测量精度要求,必须对其进行在轨辐射定标。本文基于散射计在开阔大洋的观测数据,利用经过定标的seawinds散射计后向散射系数数据,分析了海洋目标定标法的定标精度,结果表明定标精度可以达到0.15 dB,且模式函数对定标结果的影响为系统偏差,说明海洋目标定标法需要选用高精度的模式函数。然后,采用相同的海洋目标定标算法,实现了HY-2A卫星微波散射计的在轨辐射定标,获得HY-2A卫星微波散射计VV极化的定标系数为-1.79 dB,HH极化的定标系数为-1.73 dB。最后,利用NDBC浮标观测数据,检验HY-2A卫星微波散射计反演的风矢量精度,证明获得的定标系数可以明显提高HY-2A卫星微波散射计反演风矢量的精度。  相似文献