Some applications of humidity profiles estimated from INSAT infra red digital cloud imagery data     

Onkari Prasad  Sant Prasad  Kanti Prasad  R. R. Kelkar 《Journal of Earth System Science》1998,107(1):5-18

Moisture profiles have been estimated over the region bounded by the latitudes 40°N and 40°S and longitudes 30°E to 130°E using INSAT digital infra red cloud imagery data. The representativeness of these profiles in representing moisture field associated with the development and movement of synoptic scale systems during the period September 15th, 1996 to March 31st, 1997 has been examined. It has been shown that the changes in the moisture field associated with the withdrawal of the southwest and northeast monsoons from the Indian sub-continent, development and movement of synoptic scale sytems (depressions, tropical cyclones and waves in easterlies) and equatorial troughs in the Indian Ocean could be clearly seen in humidity profiles. The initial development of tropical systems is first seen in the humidity field in the upper troposphere. These profiles could be used in monitoring the initial development and subsequent movement of tropical systems. Further the data on moisture distribution from the data gap regions of the Indian Ocean could be used as an additional source of moisture in numerical analysis and prognosis.  相似文献   

Separation of ocean features from multifrequency full-polarization SAR imagery     

YANG Jingsong  XIAO Qingmei  HUANG Weigen  FU Bin  CHEN Peng 《海洋学报(英文版)》2008,27(Z1):155-158

Different ocean features usually appear in synthetic aperture radar (SAR) images simultaneously. This makes the image compli- cated and hard to understand. Because of lower signal-to-noise rate , it is much more difficult to separate different ocean features than to separate different land features. A completely novel method is presented to separate ocean features from multifrequency po- larimetric SAR imagery. AIRSAR data from Jet Propulsion Laboratory (JPL), National Aeronautics and Space Administration (NASA) are used in the case studies and good results are achieved.  相似文献   

Global distribution of summer chlorophyll blooms in the oligotrophic gyres     

Cara Wilson  Xuemei Qiu 《Progress in Oceanography》2008,78(2):107-134

Chlorophyll blooms consistently develop in the oligotrophic NE Pacific in late summer, isolated from land masses and sources of higher chlorophyll waters. These blooms are potentially driven by nitrogen fixation, or by vertically migrating phytoplankton, and a better understanding of their ubiquity could improve our estimate of the global nitrogen fixation rate. Here, global SeaWiFS chlorophyll data from 1997 to 2007 are examined to determine if similar blooms occur in other oligotrophic gyres. Our analysis revealed blooms in five other areas. Two of these are regions where blooms have been previously identified: the SW Pacific and off the southern tip of Madagascar. Previously, unnoticed summer blooms were also identified in the NE and SW Atlantic and in a band along 10°S in the Indian Ocean. There is considerable variation in the intensity and frequency of blooms in the different regions, occurring the least frequently in the Atlantic Ocean. The blooms that develop along 10°S in the Indian Ocean are unique in that they are clearly associated with a hydrographic feature, the 10°S thermocline ridge, which explains the bloom within a conventional upwelling scenario. The environment and timing of the blooms, developing in oligotrophic waters in late summer, are conducive to both nitrogen fixers and vertically migrating phytoplankton, which require a relatively stable water column. However, the specific locations of the chlorophyll blooms generally do not coincide with areas of maximum levels of nitrogen fixation or Trichodesmium. The NE Pacific chlorophyll blooms develop in a region with a very high SiO₄/NO₃ ratio, where silicate will not be a limiting nutrient for diatoms. The blooms often develop between eddies, wrapping around the periphery of anti-cyclonic features. However, none of the areas where the blooms develop have particularly high eddy kinetic energy, from either a basin-scale or a mesoscale perspective, suggesting that other factors, such as interactions with a front or dynamics associated with the critical latitude, operate in conjunction with the eddy field to produce the observed blooms.  相似文献   

高分辨SAR-GEC影像严密成像几何模型及其应用研究   总被引：1，自引：0，他引：1  

张过  祝彦敏  费文波  李德仁 《测绘通报》2009,(5)

提出并构建SAR影像GEC(Geocoded Ellipsoid Corrected)产品严密成像几何模型,并在此基础上研究用RPC模型替代SAR影像GEC产品严密成像几何模型的町行性以及基于RPC模型的GEC产品的定向和纠正.最后用TerraSAR-X影像验证其理论和算法,得到如下结论:针对高分辨SAR影像GEC级别产晶的严密成像几何模型能用于SAR影像的定向以及正射纠正.  相似文献   

差分InSAR处理及其应用分析   总被引：5，自引：0，他引：5  

张景发  李发祥  刘钊 《地球信息科学学报》2000,2(3):58-64

本文结合实例分析和介绍了影响In SAR处理结果的几个重要环节。如: 数据源及像对选择 ;影响In SAR处理的因素等。目前有4～5种雷达卫星数据可以用于In SAR的处理,ERS-1/2卫星数据效果最好; 差分In SAR处理的工作步骤中,亚像元精度的配准、相干性分析、全相位恢复等是其中的关键技术。In SAR的精度和噪声水平是In SAR能否实用的重要条件,噪声影响地物的相干性,噪声较大部位相干性消失,在整幅图像中噪声区域不大于30% ,将不影响整体的In SAR测量结果。  相似文献   

A data assimilation approach to discharge estimation from space     

Jeffrey Neal  Guy Schumann  Paul Bates  Wouter Buytaert  Patrick Matgen  Florian Pappenberger 《水文研究》2009,23(25):3641-3649

River discharge is currently monitored by a diminishing network of gauges, which provide a spatially incomplete picture of global discharges. This study assimilated water level information derived from a fused satellite Synthetic Aperture Radar (SAR) image and digital terrain model (DTM) with simulations from a coupled hydrological and hydrodynamic model to estimate discharge in an un‐gauged basin scenario. Assimilating water level measurements led to a 79% reduction in ensemble discharge uncertainty over the coupled hydrological hydrodynamic model alone. Measurement bias was evident, but the method still provided a means of improving estimates of discharge for high flows. The study demonstrates the potential of currently available synthetic aperture radar imagery to reduce discharge uncertainty in un‐gauged basins when combined with model simulations in a data assimilation framework, where sufficient topographic data are available. The work is timely because in the near future the launch of satellite radar missions will lead to a significant increase in the volume of data available for space‐borne discharge estimation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

多波段海洋内波SAR图像特征分析   总被引：1，自引：0，他引：1  

范开国  黄韦艮  贺明霞  傅斌 《海洋通报》2008,27(6)

利用 SIR-C/X-SAR 南海海域多波段数据,分析了海洋内波 SAR 图像特征与雷达波段的关系.对上升型和下降型的海洋内波 SAR 图像,内波图像特征在 X 波段最为明显,C 波段次之,L 波段最弱.利用布拉格共振散射理论分析了内波图像特征在不同波段存在差异的原因.基于 M4S 海面微波成像仿真软件,模拟分析了不同波段的海洋内波 SAR 图像特征,模拟分析结果与数据分析结果吻合较好.  相似文献   

D—InSAR三轨法监测城市地表沉降的研究     

胡波  蒋弥  王兴旺  孙倩 《测绘工程》2009,18(2):46-50

差分干涉测量（DInSAR）技术是合成孔径雷达（SAR）卫星应用的一个拓展。雷达图象的差分干涉可用于监测厘米级或更微小的地表形变，以揭示许多物理现象，如地震形变、火山运动、大气变化、冰川漂移、地面沉降以及山体滑坡等。实验选取典型的上海市地面沉降场作为研究对象，使用三幅欧洲空间局ERS1和ERS2的C波段数据，采用三轨法，成功提取了上海市相隔20个月的地面沉降图。  相似文献   

坐标转换在隐蔽物探测定位中的应用     

张子善  李杨寰  张汉华  黎向阳 《测绘与空间地理信息》2009,32(5):196-199

以基于低空平台的超宽带合成孔径雷达（UWB SAR）探测隐蔽物为应用背景,结合GPS RTK（Real Time Kinetic）技术,提出并详细分析了一种简便实用的对平台进行高精度、高动态运动补偿的GPS坐标转换方法。利用转换后的坐标和雷达回波数据对探测区成像,并对目标进行大地坐标定位,最后通过实验结果验证了本文所提方法的有效性。  相似文献   

Use of SPOT 5 and IKONOS imagery for mapping biocenoses in a Tunisian Coastal Lagoon (Mediterranean Sea)     

A. Vela  V. Pasqualini  V. Leoni  A. Djelouli  H. Langar  G. Pergent  C. Pergent-Martini  L. Ferrat  M. Ridha  H. Djabou 《Estuarine, Coastal and Shelf Science》2008,79(4):591-598

Mapping marine biocenoses is an efficient method for providing useful data for the management and conservation of Mediterranean lagoons. Fused images from two satellites, SPOT 5 and IKONOS, were tested as management tools for identifying specific ecosystems in the El Bibane lagoon, situated in southern Tunisia near the Libyan border. The objectives of this study were to provide a precise map of the entire El Bibane lagoon using fused images from SPOT 5 and to compare fused images from SPOT 5 and IKONOS over a test-area. After applying a supervised classification, pixels are automatically classified in four classes: low seagrass cover, high seagrass cover, superficial mobile sediments and deep mobile sediments. The maps of the lagoon revealed and confirmed an extremely wide distribution of seagrass meadows within the lagoon (essentially Cymodocea nodosa; 19 546 ha) and a large area of mobile sediments more or less parallel to the shore (3 697 ha). A direct comparison of overall accuracy between SPOT 5 over the entire area, SPOT 5 over the test-area and IKONOS over the test-area revealed that these tools provided accurate mapping of the lagoon environment (83.25%, 85.91% and 73.41% accuracy, respectively). The SPOT 5 images provided greater overall accuracy than the IKONOS image, but did not take into account the heterogeneous spatial structure of the seagrasses and sediments present in the lagoon environment. Although IKONOS imagery provided lower overall accuracy than SPOT 5, it proved a very useful tool for the mapping of heterogeneous structures as it enabled the patchiness of formations to be better taken into account. The use of SPOT 5 and IKONOS fused images appears to be very promising for completing the mapping of lagoons in other regions and countries of the Mediterranean Sea.  相似文献