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Comparison of sea surface wind field measured by HY-2A scatterometer and WindSat in global oceans

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Journal of Oceanology and Limnology 2019年第1期37卷 38-46页

作者： ZHENG Minwei LI Xiao-Ming SHA Jin Key Laboratory of Digital Earth Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences University of Chinese Academy of Sciences laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Hainan key laboratory of earth Observation

In this study, we present a comprehensive comparison of the sea surface wind ?eld measured by scatterometer(Ku-band scatterometer) aboard the Chinese HY-2 A satellite and the full-polarimetric radiometer WindSat aboard the Coriolis satellite. The two datasets cover a four-year period from October2011 to September 2015 in the global oceans. For the sea surface wind speed, the statistical comparison indicates good agreement between the HY-2 A scatterometer and WindSat with a bias of nearly 0 m/s and a root mean square error(RMSE) of 1.13 m/s. For the sea surface wind direction, a bias of 1.41° and an RMSE of 20.39° were achieved after excluding the data collocated with opposing directions. Furthermore,discrepancies in sea surface wind speed measured by the two sensors in the global oceans were investigated.It is found that the larger dif ferences mainly appear in the westerlies in the both hemispheres. Both the bias and RMSE show latitude dependence, i.e., they have signi?cant latitudinal ?uctuations.

关键词： sea surface wind feld global comparisons HY-2A scatterometer polarimetric radiometer WindSat

The Geological Significance of a Tuffite Interlayer in the Cretaceous Port Island Formation in Northeastern Hong Kong

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Acta Geologica Sinica(English Edition) 2018年第3期92卷 1041-1052页

作者： ZHAO Longlong WANG Lulin TIAN Mingzhong WU Fadong Key Laboratory of Digital Earth Science Institute of Remote Sensing and Digital EarthChinese Academy of Sciences School of earth Science and Resources China University of Geosciences

The Port Island Formation(PIF), a typical Cretaceous red bed in Hong Kong, is dominated by non-fossiliferous, reddish clastic rocks, making it difficult to determine the sedimentary age of PIF precisely. Previous studies assigned the PIF to Late Cretaceous provisionally only on the basis of its stratigraphic sequence and lithology. This study identified a tuffite interlayer in the PIF and a zircon UPb age of 128.2±2.7 Ma by LA-ICP-MS method was obtained. It’s the first time to date the depositional age of the PIF with a reliable chronological constraint. With the support of stratigraphic evidence, we concluded that the geological age of PIF should be Early Cretaceous rather than Late Cretaceous. Based on the volcanic history of Hong Kong and Southeast China and the distribution of the PIF in Mirs Bay, it is believed that there was no volcanic activity in Hong Kong in ca. 128 Ma. The tuffite interlayer discovered in PIF was formed by the deposition of volcanic ash, which might originate from remote region outside Hong Kong, in an aquatic environment on Port Island. The identification of the tuffite interlayer, as the response to a volcanic event, has great significance not only to the studies of establishment and regional correlation of the strata system and the geological evolution in Hong Kong,but also to the study of volcanic activities in Southeast China.

关键词： tuffite LA-ICP-MS zircon U-Pb dating Port Island Formation Early Cretaceous volcanic activities Hong Kong China

Linking satellite-based spring phenology to temperate deciduous broadleaf forest photosynthesis activity

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International Journal of digital earth 2014年第11期7卷 881-896页

作者： Jing-Jing Zhao Liang-Yun Liu Key Laboratory of Digital Earth Science Center for Earth Observation and Digital EarthUniversity of Chinese Academy of SciencesBeijingChina

Satellite-based remote sensed phenology has been widely used to assess global climate change.However,it is constrained by uncertain linkages with photo-synthesis activity.Two dynamic threshold methods were employed to retrieve spring phenology metrics from four Moderate Resolution Imaging Spectro-radiometer(MODIS)products,including fraction of Absorbed Photosyntheti-cally Active Radiation(fAPAR),Leaf Area Index(LAI),Normalized Difference Vegetation Index(NDVI),and Enhanced Vegetation Index(EVI)for three temperate deciduous broadleaf forests in North America between 2001 and 2009.These MODIS-based spring phenology metrics were subsequently linked to the photosynthetic curves(daily gross primary productivity,GPP)measured by an eddy covariance flux tower.The 20% dynamic threshold spring onset metrics from MODIS products were closer to the photosynthesis onset metrics at the date of 2% GPP increase for NDVI and fAPAR,and closer to the date of 5%and 10% increase of GPP for EVI and LAI,respectively.The 50% dynamic threshold onset metrics were closer to the photosynthesis onset metrics at the date of 10%GPP increase for NDVI,and closer to the date of 20% GPP increase for fAPAR,LAI and EVI,respectively.These results can improve our knowledge on the photosynthesis activity status of remotely sensed spring phenology metrics.

关键词： MODIS spring phenology deciduous broadleaf forest GPP eddy covariance flux tower photosynthesis activity period

Scientific big data and digital earth

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Chinese Science Bulletin 2014年第35期59卷 5066-5073页

作者： Huadong Guo Lizhe Wang Fang Chen Dong Liang Key Laboratory of Digital Earth Sciences Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences

Big data has been a focus of research in science,technology,economics,and social studies.Many countries have already incorporated big data research into their national strategies.This paper elaborates upon the origin,connotation,and development of big data from both a spatial and temporal perspective.It proposes that scientific big data will become a new solution in scientific research as the paradigm changes from being model-driven to data-driven.This paper defines the concept of ‘‘scientific big data'' and proposes strategies for solving ‘‘big data problems' '.Theoretical frameworks and data systems for digital earth are discussed with a clear conclusion that scientific big data is a prominent feature of digital earth.As an example,spatial cognition of the formation mechanism of China's Heihe-Tengchong Line—a geo-demographic demarcation line dividing China into two parts—is discussed within the context of big data computation and analysis for digital earth.

关键词：科学研究数字地球社会研究国家战略空间角度模型驱动数据驱动数据系统

Simulation analysis on the relationship between the leaf area index and polarimetric parameters of crops

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International Journal of digital earth 2012年第4期5卷 319-337页

作者： Lu Zhang Huadong Guo Xinwu Li The Key Laboratory of Digital Earth Center for Earth Observation and Digital EarthChinese Academy of SciencesBeijing 100094China

The leaf area index(LAI)is an important parameter to quantitatively describe the structure of vegetation and crops.Uncertainty in the relationship between the LAI and polarimetric parameters is the key problem for LAI estimation from polarimetric synthetic aperture radar(POLSAR)data.However,the existing POLSAR data have difficulties meeting the demand of the aforementioned research.This paper analyses the correlations between the LAI and the polarimetric parameters derived from Cloude and Freeman decompositions using simulated POLSAR data based on a coherent scattering model for maize and wheat.The results show:(1)The POLSAR data at C-band with a large incidence angle(40 degrees)are very suitable for finding the LAI for maize and wheat.(2)For maize there is a strong correlation between the scattering type angle and the LAI at C-band with a large incidence angle,and the coherency entropy,anisotropy,and the power of the double-bounce scattering power component also have significant correlations with the LAI.(3)For wheat at Cband with a high incidence angle,although the correlation coefficient is low,there is still a correlation between the entropy,anisotropy and LAI.Besides,the volume scattering is suitable for extracting the LAI for wheat at X-band.

关键词： POLSAR simulation LAI polarimetric parameter digital earth

Antarctic ice-sheet near-surface snowmelt detection based on the synergy of SSM/I data and QuikSCAT data

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Geoscience Frontiers 2018年第3期9卷 955-963页

作者： Xing-Dong Wang Xin-Wu Li Cheng Wang Xin-Guang Li College of Information Science and Engineering Henan University of Technology Key Laboratory of Digital Earth Institute of Remote Sensing & Digital EarthChinese Academy of Sciences

Microwave radiometer SSM/I data and scatterometer QuikSCAT data have been widely used for the icesheet near-surface snowmelt detection based on their sensitivity to liquid water present in snow. In order to improve the Antarctic ice-sheet near-surface snowmelt detection accuracy, a new Antarctic icesheet near-surface snowmelt synergistic detection method was proposed based on the principle of complementary advantages of SSM/I data(high reliability) and QuikSCAT data(high sensitivity) by the use of edge detection model to automatically extract the edge information to get the distribution of Antarctic snowmelt onset date, snowmelt duration and snowmelt end date. The verification result shows that the proposed snowmelt synergistic detection method improves the detection accuracy from about 75% to 86% based on AWS(Automatic Weather Stations) Butler Island and Larsen Ice Shelf. The algorithm can also be applied to other regions, which provides methodological support and supplement for the global snowmelt detection.

关键词： Snowmelt detection SSM/I data QuikSCAT data Synergy Edge detection model

Comparision of Methods for Polarimetric SAR Tomography with Small Number of Baselines in Forested Areas

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Chinese Journal of Electronics 2019年第5期28卷 1073-1079页

作者： LIANG Lei ZHOU Chenghu LI Xinwu GAO Xizhang WU Wenjin State key laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Key Laboratory of Digital Earth Sciences Institute of Remote Sensing and Digital Earth (RADI) Chinese Academy of Sciences

Synthetic aperture radar Tomography(TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. However, the more multi-baselines acquisition, the longer the time span of acquisition, which will result in serious temporal decorrelation in forested area. In this way, we expect to use as smaller number of baselines as possible to obtain high estimation accuracy in elevation direction. We thus investigate the performance of Polarimetric SAR tomography(Pol-TomoSAR) with small number of baselines in forested areas. The results show that compressive sensingbased Pol-TomoSAR has higher estimation accuracy in elevation direction than conventional Pol-TomoSAR with small number of baselines.

关键词： Synthetic aperture radar(SAR) Polarimetric SAR SAR tomography Compressive sensing

Gap analysis on open data interconnectivity for disaster risk research

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Geo-Spatial Information Science 2019年第1期22卷 45-58页

作者： Guoqing Li Jing Zhao Virginia Murray Carol Song Lianchong Zhang Key Laboratory of Digital Earth Science Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijingChina Hainan key laboratory of earth Observation SanyaChina Institute of Remote Sensing and digital earth University of Chinese Academy of SciencesBeijingChina Public Health England Health and Social CareLondonUK Rosen Centre for Advance Computing Purdue UniversityWest LafayetteINUSA

Open data strategies are being adopted in disaster-related data particularly because of the need to provide information on global targets and indicators for implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030.In all phases of disaster risk management including forecasting,emergency response and post-disaster reconstruction,the need for interconnected multidisciplinary open data for collaborative reporting as well as study and analysis are apparent,in order to determine disaster impact data in timely and reportable manner.The extraordinary progress in computing and information technology in the past decade,such as broad local and wide-area network connectivity(***),highperformance computing,service and cloud computing,big data methods and mobile devices,provides the technical foundation for connecting open data to support disaster risk research.A new generation of disaster data infrastructure based on interconnected open data is evolving rapidly.There are two levels in the conceptual model of Linked Open Data for Global Disaster Risk Research(LODGD)Working Group of the Committee on Data for Science and Technology(CODATA),which is the Committee on Data of the International Council for Science(ICSU):data characterization and data connection.In data characterization,the knowledge about disaster taxonomy and data dependency on disaster events requires specific scientific study as it aims to understand and present the correlation between specific disaster events and scientific data through the integration of literature analysis and semantic knowledge discovery.Data connection concepts deal with technical methods to connect distributed data resources identified by data characterization of disaster type.In the science community,interconnected open data for disaster risk impact assessment are beginning to influence how disaster data are shared,and this will need to extend data coverage and provide better ways of utilizing data across domains where innovation and integration are now necessarily nee

关键词： Open data interconnectivity gap analysis disaster risk

The measurement and model construction of complex permittivity of vegetation

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Science China earth Sciences 2014年第3期57卷 729-740页

作者： LI Zhen ZENG JiangYuan CHEN Quan BI HaiYun Key Laboratory of Digital Earth Science Institute of Remote Sensing and Digital EarthChinese Academy of Sciences University of Chinese Academy of Sciences

The complex permittivity of targeted objects is an important factor that influences its microwave radiation and scattering characteristics.In the quantitative research of microwave remote sensing,the study of the dielectric properties of the vegetation to establish the relationship between its specific physical parameters and complex permittivity is fundamental.In this study,six categories of vegetation samples were collected at the city of Zhangye,a key research area of the Heihe watershed allied telemetry experimental research.The vector network analyzer E8362B was used to measure the complex permittivity of these samples from 0.2 to 20 GHz by the coaxial probe technique.The research focused mainly on the corn leaves,and an empirical model was established between the gravimetric moisture and the real/imaginary parts of complex permittivity at the main frequency points of microwave sensors.Furthermore,the empirical model and the classical Debye-Cole model were compared and verified by the measured data collected from the Huailai County of Hebei Province.The results show that the newly- established empirical model is more accurate and more practical as compared to the traditional Debye-Cole model.

关键词：复介电常数模型构建测量数据植被矢量网络分析仪植物样品微波传感器散射特性

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