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Improving Simulations of Vegetation Dynamics over the Tibetan Plateau:Role of Atmospheric Forcing Data and spatial resolution

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Advances in Atmospheric Sciences 2022年第7期39卷 1115-1132,I0018-I0022页

作者： Zhijie KANG Bo QIU Zheng XIANG Ye LIU Zhiqiang LIN Weidong GUO School of Atmospheric Sciences Nanjing UniversityNanjing 210046China Pacific Northwest National Laboratory Washington 99354USA Plateau Atmosphere and Environment Key Laboratory of Sichuan Province School of Atmospheric SciencesChengdu University of Information TechnologyChengdu 610225China

The efficacy of vegetation dynamics simulations in offline land surface models(LSMs)largely depends on the quality and spatial resolution of meteorological forcing *** this study,the Princeton Global Meteorological Forcing Data(PMFD)and the high spatial resolution and upscaled China Meteorological Forcing Data(CMFD)were used to drive the Simplified Simple Biosphere model version 4/Top-down Representation of Interactive Foliage and Flora Including Dynamics(SSiB4/TRIFFID)and investigate how meteorological forcing datasets with different spatial resolutions affect simulations over the Tibetan Plateau(TP),a region with complex topography and sparse *** comparing the monthly Leaf Area Index(LAI)and Gross Primary Production(GPP)against observations,we found that SSiB4/TRIFFID driven by upscaled CMFD improved the performance in simulating the spatial distributions of LAI and GPP over the TP,reducing RMSEs by 24.3%and 20.5%,*** multi-year averaged GPP decreased from 364.68 gC m^(-2)yr^(-1)to 241.21 gC m^(-2)yr^(-1)with the percentage bias dropping from 50.2%to-1.7%.When using the high spatial resolution CMFD,the RMSEs of the spatial distributions of LAI and GPP simulations were further reduced by 7.5%and 9.5%,*** study highlights the importance of more realistic and high-resolution forcing data in simulating vegetation growth and carbon exchange between the atmosphere and biosphere over the TP.

关键词： SSiB4 meteorological forcing data vegetation dynamics spatial resolution Tibetan Plateau

Areal density and spatial resolution of high energy electron radiography

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Chinese Physics B 2018年第3期27卷 321-326页

作者：肖家浩张子民曹树春袁平申晓康程锐赵全堂宗阳刘铭周贤明李中平赵永涛唐传祥黄文会杜应超盖炜 Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China Department of Engineering Physics Tsinghua UniversityBeijing 100084China Argonne National Lab ArgonneIL 60439USA

Ultrafast imaging tools are of great importance for determining the dynamic density distribution in high energy density （HED） matter. In this work, we designed a high energy electron radiography （HEER） system based on a linear electron accelerator to evaluate its capability for imaging HED matter. 40 MeV electron beams were used to image an aluminum target to study the density resolution and spatial resolution of HEER. The results demonstrate a spatial resolution of tens of micrometers. The interaction of the beams with the target and the beam transport of the transmitted electrons are further simulated with EGS5 and PARMELA codes, with the results showing good agreement with the experimental resolution. Furthermore, the experiment can be improved by adding an aperture at the Fourier plane.

关键词： high energy density matter high energy electron radiography areal density resolution spatial resolution

Effects of spatial resolution of remotely sensed data on estimating urban impervious surfaces

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Journal of Environmental Sciences 2011年第8期23卷 1375-1383页

作者： Weifeng Li Zhiyun Ouyang Weiqi Zhou Qiuwen Chen State Key laboratory of Urban and Region Ecology Research Centre for Eco-Environmental Sciences Chinese Academy of Sciences Beijing1000~85 China. Department of Plant Sciences University of California Davis Mail Stop 1 1210 PES One Shields Ave. Davis CA 95616 USA

Impervious surfaces are the result of urbanization that can be explicitly quantified, managed and controlled at each stage of land development. It is a very useful environmental indicator that can be used to measure the impacts of urbanization on surface runoff, water quality, air quality, biodiversity and rnicroclimate. Therefore, accurate estimation of impervious surfaces is critical for urban environmental monitoring, land management, decision-making and urban planning. Many approaches have been developed to estimate surface imperviousness, using remotely sensed data with various spatial resolutions. However, few studies, have investigated the effects of spatial resolution on estimating surface imperviousness. We compare medium-resolution Landsat data with high-resolution SPOT images to quantify the imperviousness in Beijing, China. The results indicated that the overall 91% accuracy of estimates of imperviousness based on TM data was considerably higher than the 81% accuracy of the SPOT data. The higher resolution SPOT data did not always predict the imperviousness of the land better than the TM data. At the whole city level, the TM data better predicts the percentage cover of impervious surfaces. At the sub-city level, however, the ring belts from the central core to the urban-rural peripheral, the SPOT data may better predict the imperviousness. These results highlighted the need to combine multiple resolution data to quantify the percentage of imperviousness, as higher resolution data do not necessarily lead to more accurate estimates. The methodology and results in this study can be utilized to identify the most suitable remote sensing data to quickly and efficiently extract the pattern of the impervious land, which could provide the base for further study on many related urban environmental problems.

关键词： remote sensing impervious surface landscape pattern spatial resolution object-based image analysis urban landscape

On the effects of spatial resolution on effective distance measurement in digital landscapes

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Ecological Processes 2021年第1期10卷 659-677页

作者： Rachel Mundeli Murekatete Takeshi Shirabe KTH Royal Institute of Technology School of Architecture and the Built EnvironmentTeknikringen 10A11428 StockholmSweden University of Rwanda College of Science and TechnologyCentre for Geographic Information Systems and Remote SensingKN 67 Street NyarugengeKigaliRwanda

Background:Connectivity is an important landscape attribute in ecological studies and conservation practices and is often expressed in terms of effective *** the cost of movement of an organism over a landscape is effectively represented by a raster surface,effective distances can be equated with the cost-weighted distance of least-cost *** is generally recognized that this measure is sensitive to the grid’s cell size,but little is known if it is always sensitive in the same way and to the same degree and if not,what makes it more(or less)*** conducted computational experiments with both synthetic and real landscape data,in which we generated and analyzed large samples of effective distances measured on cost surfaces of varying cell sizes derived from those *** particular focus was on the statistical behavior of the ratio—referred to as‘accuracy indicator’—of the effective distance measured on a lower-resolution cost surface to that measured on a higher-resolution cost ***:In the experiment with synthetic cost surfaces,the sample values of the accuracy indicator were generally clustered around 1,but slightly greater with the absence of linear sequences(or barriers)of high-cost or inadmissible cells and smaller with the presence of such *** latter tendency was more dominant,and both tendencies became more pronounced as the difference between the spatial resolutions of the associated cost surfaces *** two real satellite images(of different resolutions with fairly large discrepancies)were used as the basis of cost estimation,the variation of the accuracy indicator was found to be substantially large in the vicinity(1500 m)of the source but decreases quickly with an increase in distance from ***:Effective distances measured on lower-resolution cost surfaces are generally highly correlated with—and useful predictors of—effective distances measured on higher-resolution cost *** relationship t

关键词： Landscape connectivity Effective distance Raster-based least-cost path model Accuracy spatial resolution

Beam hardening correction for a cone-beam CT system and its effect on spatial resolution

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Chinese Physics C 2011年第10期35卷 978-985页

作者：赵维付国涛孙翠丽王燕芳魏存峰曹大泉阙介民唐晓史戒坚魏龙郁忠强 Key Laboratory of Nuclear Analytical Techniques Institute of High Energy PhysicsCAS Beijing Engineering Research Center of Radiographic Techniques and Equipment Graduate University of Chinese Academy of Sciences

In this paper, we present a beam hardening correction （BHC） method in three-dimension space for a cone-beam computed tomography （CBCT） system in a mono-material case and investigate its effect on the spatial resolution. Due to the polychromatic character of the X-ray spectrum used, cupping and streak artifacts called beam hardening artifacts arise in the reconstructed CT images, causing reduced image quality. In addition, enhanced edges are introduced in the reconstructed CT images because of the beam hardening effect. The spatial resolution of the CBCT system is calculated from the edge response function （ERF） on different planes in space. Thus, in the CT images with beam hardening artifacts, enhanced ERFs will be extracted to calculate the modulation transfer function （MTF）, obtaining a better spatial resolution that deviates from the real value. Reasonable spatial resolution can be obtained after reducing the artifacts. The 10% MTF value and the full width at half maximum （FWHM） of the point spread function with and without BHC are presented.

关键词： beam hardening correction cone-beam computed tomography spatial resolution

Optimization of the in-line X-ray phase-contrast imaging setup considering edge-contrast enhancement and spatial resolution

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Chinese Physics C 2012年第3期36卷 267-274页

作者：贾全杰陈雨黎刚姜晓明 Institute of High Energy Physics Chinese Academy of Sciences

Employing the approximation theory based on refraction and the definition of the total pointspread-function of the imaging system, the variation in the edge contrast of simple model samples is discussed with different source-to-sample and sample-to-detector distances, which actually means different spatial resolutions of the imaging system. The experiments were carried out with the Beamline 4W1A imaging setup at the Beijing Synchrotron Radiation Facility for simple model and insect samples. The results show that to obtain clear phase-contrast images of biologic tissues for the X-ray in-line imaging setup, with determined parameters such as the size of the X-ray source, the pixel size of the detector and the fixed source-to-sample distance, there is a range of optimized sample-to-detector distances. The analysis method discussed in this article can be helpful in optimizing the setup of X-ray in-line phase-contrast imaging.

关键词： X-ray phase contrast imaging edge-contrast enhancement spatial resolution

Study of measuring methods on spatial resolution of a GEM imaging detector

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Chinese Physics C 2012年第3期36卷 228-234页

作者：吕新宇樊瑞睿陈元柏欧阳群刘荣光刘鹏祁辉荣张健赵平平赵东旭赵豫斌章红宇盛华义董丽媛 Institute of High Energy Physics Chinese Academy of Sciences Graduate University of Chinese Academy of Sciences State Key Laboratory of Particle Detection and Electronics School of Nuclear Science and Technology Lanzhou University

In this paper, the limitations of the common method measuring intrinsic spatial resolution of the GEM imaging detector are presented. Through theoretical analysis and experimental verification, we have improved the common method to avoid these limitations. Using these improved methods, a more precise measurement of intrinsic spatial resolutions are obtained.

关键词： spatial resolution imaging detector GEM convolution deconvolution

Study on spatial resolution of micromegas as a neutron detector under condition of high neutron flux and γ ray background

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Chinese Physics C 2009年第2期33卷 110-113页

作者：王文昕张毅王集锦胡碧涛 School of Nuclear Science and Technology Lanzhou University

In this paper Micromegas has been designed to detect neutrons. The simulation of the spatial resolution of Micromegas as neutron detector is carried out by GEANT4 toolkit. The neutron track reconstruction method based on the time coincidence technology is employed in the present work. The influence of the flux of incident 14 MeV neutron and high gamma background on the spatial resolution is carefully studied. Our results show that the spatial resolution of the detector is sensitive to the neutron flux, but insensitive to the intensity of γ background if the neutron track reconstruction method proposed by our group is used. The γ insensitivity makes it possible for us to use the Micromegas detector under condition which has high γ-rays background.

关键词： micromegas neutron detection GEANT4 spatial resolution γ sensitivity

A sub-millimeter spatial resolution achieved by a large sized glass RPC

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Chinese Physics C 2013年第1期37卷 76-79页

作者：李奇特叶沿林纪玮文超刘洪涛葛愉成 School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University

Three large sized glass resistive plate chambers （RPCs） are built and applied to measure the spatial resolution of the detector. The readout strips are collected to a LC delay-line and the time difference is used to determine the position. Cosmic rays are triggered by a set of two scintillation counters and the coincidently measured positions from the three RPCs are used to deduce the position uncertainty. In average a spatial resolution of 0.90 mm （FWHM） is obtained for a single RPC, with a good uniformity across the detection area. This result suggests that large sized glass RPC operating in the avalanche mode is a promising candidate for the muon tomography detection system.

关键词： RPC spatial resolution cosmic ray delay-line