共查询到17条相似文献,搜索用时 281 毫秒
1.
2.
地球物理模式函数GMF (Geophysical Model Function)在星载微波散射计海面风场反演中具有关键作用。本文以C波段MetOp/ASCAT散射计风场数据为参考数据,通过改进现有Ku波段NSCAT-4 GMF中后向散射系数对海面风速和风向的依赖关系,以及增加海表温度(SST)因子项,构建了适用于HY-2卫星微波散射计海面风场反演的NSCAT-5.HY-2 GMF。研究结果表明,相比NSCAT-4 GMF,采用NSCAT-5.HY-2 GMF反演得到的HY-2散射计海面风速与ASCAT散射计风速的一致性提高了约11%,特别是风速反演误差不再依赖于SST变化、不再呈现显著经向分布特点。本论文研究结果对进一步提升国内外其他Ku波段星载微波散射计数据的海面风场遥感应用具有重要参考价值。 相似文献
3.
旋转扫描散射计海面风场检测仿真研究 总被引:7,自引:0,他引:7
该文对Ku波段旋转扫描星载散射计进行了仿真研究。通过仿真模型建立,分辨面元提取与风矢量模糊解消除,分析了散射计地面与星载定标特性,给出了散射度工作特性仿真结果。通过对均匀旋涡两种模拟输入风场的仿真,表明这种旋转扫描散射计风场检测及利用Moore方程进行风场反演的有效性。 相似文献
4.
面元匹配是散射计海面风场反演的重要预处理步骤。为保障海洋二号卫星散射计(HSCAT)业务化海面风场反演,提出了一种可业务化运行的HSCAT面元匹配算法。HSCAT面元匹配算法包括地面网格划分和后向散射系数观测结果重采样两个关键部分。为简化计算,HSCAT采用以星下点轨迹为中心,以顺轨向及交轨向为坐标轴,分辨率为25 km×25 km的网格划分方式。重采样利用卫星星下点经纬度数据,对每个后向散射系数观测结果,以后向散射系数与各星下点球面距离的最小值为依据进行交轨向重采样,并以取得距离最小值所对应的星下点与该轨数据星下点起始位置的距离为依据进行顺轨向重采样,实现对后向散射系数观测结果的面元匹配。实验和对比结果表明,提出的面元匹配算法可对后向散射系数进行有效的重采样,风矢量面元的位置分布均匀,每个风矢量面元均有足够数量的独立观测后向散射系数,可在全球范围内满足高质量海面风场反演的要求。 相似文献
5.
6.
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
7.
8.
ERS散射计全球海面风场数据处理与ElNino海面风场异常观测 总被引:1,自引:0,他引:1
星载散射测量技术是获取全球海面风场的有效手段。该文研究了欧洲遥感卫星(ERS) 散射计全球海面风场数据的处理分析技术。对1997 年3 月、6 月和12 月的全球海面风场数据进行平均处理,并同时与1996 年6 月和1995 年10 月的观测数据进行对比,利用遥感技术发现了赤道太平洋西部的风场异常,从遥感资料上分析了1997 年El Nino 现象的海面风场( 风速与风向) 异常变化特征。研究结果显示了星载微波散射计在全球变化监测中的重要作用。 相似文献
9.
10.
海洋雷达后向散射回波主要来自短重力波的Bragg 散射,这种散射与海面风场信息、边界层涡旋等密切相关。因此,可以从雷达散射截面反演风场信息。对1994 年4 月航天飞机成像雷达(SIRC/XSAR)获取的南中国海合成孔径雷达(SAR) 图像进行了分析研究。利用SIRC 数据,从SAR 图像谱提取了风向;根据CMOD4 模型,从C波段雷达后向散射系数反演风速;利用双尺度散射模型对反演的风速进行了对比分析。结果表明,从SIRC雷达数据可以反演海面风矢量,星载SAR是提取海面风场信息的有效技术手段之一。 相似文献
11.
Sandip R. Oza R. K. K. Singh N. K. Vyas B. S. Gohil Abhijit Sarkar 《Journal of the Indian Society of Remote Sensing》2011,39(2):147-152
The identification of sea-ice has frequently been cited as one of the most important tasks for deriving the sea-ice parameters
and to avoid erroneous retrieval of wind vector over sea-ice infested oceans using space-borne scatterometer data. Discrimination
between sea-ice and ocean is ambiguous under the high wind and/or thin/scattered ice conditions. The pre-launch technique
developed for Oceansat-2, utilizes the dual-polarized QuikSCAT scatterometer data by using the spatio-temporal coherence properties
of sea ice in addition to backscatter coefficient and the Active Polarization Ratio. Results were compared with the operational
sea-ice products from National Snow and Ice Data Center. The threshold API value of −0.025 was found optimum for sea-ice and
ocean discrimination. The overall sea-ice identification accuracy achieved was of the order of 95 per cent, ranging from 92.5%
(during December in Southern Hemisphere) to 98% (during March in Northern Hemisphere). The applicability of the algorithm
for both the Arctic as well as Antarctic makes it suitable for its operational use with the Oceansat-2 scatterometer data. 相似文献
12.
A Ka-band backscatter model and an algorithm for measurement of the wind speed and direction over the sea surface by a frequency-modulated continous-wave radar demonstrator system operated in scatterometer mode have been developed. To evaluate the proposed algorithm, a simulation of the wind vector retrieval has been performed. 相似文献
13.
The SeaWinds-on-QuikSCAT (QuikSCAT) and SeaWinds-on-ADEOS-2 (SeaWinds) scatterometers measure the normalized radar backscatter (/spl sigma//sup o/) of the earth's surface. These identical radar sensors are on different spaceborne platforms in similar orbits. QuikSCAT and SeaWinds data are used to infer near-surface wind vectors, polar sea-ice extent, polar-ice melt events, etc. In order to verify the relative calibration of these sensors, a simple cross calibration based on land backscatter measurements is performed. A first-order polynomial model is used to remove the incidence angle dependence of /spl sigma//sup o/ for selected regions of the Amazon rainforest and the Sahara Desert. It is shown that the two sensors are well-calibrated to each other and require no bias corrections. Additionally, evidence of a diurnal cycle in the Amazon rainforest backscatter is given. 相似文献
14.
Spaceborne passive microwave data have been available for the past 27 years, and have supported the development of several algorithms for the retrieval of snow water equivalent and snow depth that, in turn, can be used for mapping snow-covered areas. In contrast, only recently has the application of spaceborne active microwave instruments been investigated for remote sensing of snow on a global scale. This raises the question of whether a technique combining active and passive microwave data can improve the mapping of snow parameters with respect to techniques based solely on passive data. In this letter, we report results concerning the mapping of snow-covered area (SCA) in the Northern Hemisphere between the years 2000 and 2004 derived from the combination of the brightness temperatures at 19.35 and 37 GHz measured by the Special Sensor Microwave Imager Radiometer with backscatter coefficients at 13.4 GHz measured by the NASA's QuickSCAT. SCA derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) is used as a reference to evaluate the performance of the microwave-based techniques and their combination. Results show that, generally, the technique using passive data provides better agreement with MODIS SCA than the technique using only scatterometer data. However, the results when both datasets are used show considerable improvement, demonstrating the potential benefits of a multisensor approach 相似文献
15.
星载大气探测激光雷达发展与展望 总被引:3,自引:0,他引:3
从最早的星载激光雷达空间技术实验LITE出发,回顾了已成功发射的多颗星载激光雷达发展历程。详细阐述了LITE、CALIPSO等星载激光雷达在大气遥感领域,特别是气候环境变化和数值预报模式研究上所取得的成就。主要从全球气溶胶垂直结构及其辐射强迫、全球云垂直结构和特征、气溶胶-云-降水相互作用和气溶胶数据在雾-霾和沙尘天气预报中的应用等4个方面进行展开说明,并且深入分析了未来星载激光雷达在大气风场和大气成分探测方面所面临的需求和挑战。在大气风场探测需求方面,结合星载激光雷达探测优势从提高热带地区的天气预报准确率、提高非地转条件下中小尺度短时临近预报水平和填补卫星高/低空急流监测技术空白等3个方面进行详细论述。在大气成分探测需求方面,与传统被动探测仪器相比较,突出激光雷达在信噪比、CO2垂直结构和夜间探测上的明显优势。最后,指出全球风场和大气成分探测将成为未来星载激光雷达的重要发展方向。 相似文献
16.
S.R. Oza S. PanigrahyJ.S. Parihar 《International Journal of Applied Earth Observation and Geoinformation》2008
Estimation of crop area, growth and phenological information is very important for monitoring of agricultural crops. However, judicious combination of spatial and temporal data from different spectral regions is necessary to meet the requirement. This study highlights the use of active microwave QuikSCAT Ku-band scatterometer and Special Sensor Microwave/Imager (SSM/I) passive microwave radiometer data to derive information on important phenological phases of rice crop. The wetness index, a weekly composite product derived using brightness temperatures from 19, 37 and 85 GHz channels of SSM/I, was used to identify the puddling period. Ku-band scatterometer data provided the signal of transplanted rice seedlings since they acts as scatterers and increases the backscattering. Dual peak nature of temporal backscatter curve around the heading stage of rice crop was observed in Ku-band. The decrease of backscatter after first peak was associated with the threshold value of 60% crop canopy cover. The symmetric (Gaussian) and asymmetric (lognormal) curve fits were attempted to derive the date of initiation of the heading phase. The temporal signature from each of these sensors was found to complement each other in crop growth monitoring. Image showing pixel-wise timings of heading stage revealed the differences exists in various parts of the study area. 相似文献
17.
Observations of urban and suburban environments with global satellite scatterometer data 总被引:1,自引:0,他引:1
S.V. Nghiem D. Balk E. Rodriguez G. Neumann A. Sorichetta C. Small C.D. Elvidge 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(4):367-380
A global and consistent characterization of land use and land change in urban and suburban environments is crucial for many fundamental social and natural science studies and applications. Presented here is a dense sampling method (DSM) that uses satellite scatterometer data to delineate urban and intraurban areas at a posting scale of about 1 km. DSM results are analyzed together with information on population and housing censuses, with Landsat Enhanced Thematic Mapper Plus (ETM+) imagery, and with Defense Meteorological Satellite Program (DMSP) night-light data. The analyses include Dallas-Fort Worth and Phoenix in the United States, Bogotá in Colombia, Dhaka in Bangladesh, Guangzhou in China, and Quito in Ecuador. Results show that scatterometer signatures correspond to buildings and infrastructures in urban and suburban environments. City extents detected by scatterometer data are significantly smaller than city light extents, but not all urban areas are detectable by the current SeaWinds scatterometer on the QuikSCAT satellite. Core commercial and industrial areas with high buildings and large factories are identified as high-backscatter centers. Data from DSM backscatter and DMSP nighttime lights have a good correlation with population density. However, the correlation relations from the two satellite datasets are different for different cities indicating that they contain complementary information. Together with night-light and census data, DSM and satellite scatterometer data provide new observations to study global urban and suburban environments and their changes. Furthermore, the capability of DSM to identify hydrological channels on the Greenland ice sheet and ecological biomes in central Africa demonstrates that DSM can be used to observe persistent structures in natural environments at a km scale, providing contemporaneous data to study human impacts beyond urban and suburban areas. 相似文献