Streamflow variability and its relationship with climate indices in western rivers of Argentina

The objective of this study was to examine the streamflow variability of Argentinean Andean basins (22°–52°S). Trends and step changes of seven hydrological variables were analysed. In addition, relationships between the hydrological variables and Pacific Decadal Oscillation (PDO), Niño 3.4, and Southern Annular Mode (SAM) indices were analysed. Most streamflow variables showed upward trends in the northwest and central-western basins, while downward trends were identified in the Patagonia (southwestern) region. Streamflow of the central-western and Patagonian basins was positively correlated with the Niño 3.4 index. Moreover, an inverse relationship with the SAM was found in watersheds south of 37°S. Positive step changes associated with the PDO phases in the north and central-western basins in the mid-1970s were detected, while negative step changes resulted in Patagonia between 1970 and 2000. This research provides new evidence of the influence of major climate modes on streamflow variability in the western rivers of Argentina.     

Pan-sharpening quality investigation of PLÉIADES-1A images

Optical remote sensing satellites obtain MS and Pan images simultaneously over the same coverage area. Remote sensing and image processing communities are working on different pan-sharpening methods capable of taking advantage of MS and Pan images. Each remote sensing system has its own advantages and disadvantages, leading to the question ‘Which pan-sharpening method should be used for which type of imagery?’ The aim of this research is to investigate the pan-sharpening performance of PLÉIADES-1A images. For this purpose, pan-sharpened images were generated using PCA, IHS and Brovey Transform which are the most popular pan-sharpening methods. Then, the pan-sharpened images were evaluated quantitatively using Correlation Coefficient, Root Mean Square Error, Relative Average Spectral Error, Spectral Angle Mapper and Erreur Relative Globale Adimensionnelle de Synthése. In addition, pan-sharpened images were evaluated qualitatively by taking object availability and completeness into consideration.     

天津地区雨季降水异常年大气环流特征分析

利用1958—2009年天津地区和中国160站月总降水资料以及NCEP/NCAR月平均再分析数据资料集,采用相关分析和合成分析,分别研究了天津地区雨季降水的变化特征以及异常年同期（7—8月）和前期（前一年1 2月至当年6月）大气环流的特征。结果表明：天津地区的降水大部分集中于雨季且雨季降水存在着年际变化和年代际变化。天津地区雨季降水偏多年同期,西太平洋副热带高压主体偏北,天津地区西北部有低值系统发展,对流层低层有正涡度发展,辐合上升运动较强,南亚高压和高空副热带西风急流偏北,西南暖湿气流输送较强;雨季降水偏少年同期情况正好相反。此外,天津地区雨季降水与前期夏季6月SAM（南半球环状模）存在显著的反相关关系,这为天津地区雨季降水的短期气候预测提供了有参考意义的前兆信号。     

Discrimination of Different Erosion Levels of Porphyry Cu Deposits using ASTER Image Processing in Eastern Iran: a Case Study in the Maherabad, Shadan, and Chah Shaljami Areas

The Lut block, eastern Iran, is one of the most extensive Cenozoic magmatic rocks, that show suitable targets for porphyry Cu-Au and high-sulfidation epithermal Au related to porphyry Cu-Au mineralization. In this study, Advanced Spaceborne Thermal Emission and Reflection Radiometer （ASTER） was used to identify different erosion levels of three porphyry Cu deposits, including Maherabad, Shadan, and Chah Shaljami, located in the Lut block volcanic-plutonic belt. Alteration minerals, including kaolinite, dickite, alunite, jarosite, epidote, chlorite, montmorillonite, muscovite, biotite, orthoclase, gypsum, and quartz, are selected to map different alteration zones and erosion levels. Distributions of end-members are mapped by using the SAM and MTMF in VNIR and SWIR of ASTER bands and the results are evaluated against the field studies. For some end-members, the results of SAM processing are more reliable compared to the MTMF because the latter looses field spectra. The use of angle threshold in the SAM, and MF-score and infeasibility value in the MTMF or low abundance of some end-members, and finally comparison of output images of spectral processing show good correlation with alteration maps. Differentiation and explanation of various erosion levels of porphyry Cu deposits are done successfully by using the ASTER sensor data.     

基于光谱角匹配预测的高光谱图像无损压缩

在地表信息获取方面,高光谱遥感是对地观测技术的主要方法,观测同时产生了海量高光谱图像的存贮与传输问题.研究发现,高光谱图像具有独特的光谱上下文特征,可从光谱维分析高光谱图像的光谱相关性,并用光谱角来度量相邻像素间的光谱相似性的差异,探测水平或垂直光谱边界,由此提出了基于光谱角匹配预测(SAMP)的无损压缩算法.实验表明,SAMP算法的预测效果好于已有文献中提出的一些优秀算法,且具有低复杂性.     

地物波谱数据辅助的SPOT影像模拟真彩色方法研究

提出一种新的高分辨率遥感影像真彩色模拟方法。该方法从遥感成像光谱角度,依据地物波谱特性,采用光谱角匹配模型(SAM),首先计算出地物在绿(G)、红(R)、近红外(NIR)以及短波红外(SWIR)波段的整体和局部波谱向量角;然后根据角度距离构建最小距离隶属函数,查找对应地物波谱库中最为相似的地物波谱;最后对此条地物波谱曲线积分计算出该像素点在蓝波段的反射率。实验表明,该方法模拟出的SPOT真彩色影像在视觉效果和空间信息上优于传统的方法。