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| 1 | Retrieval of global terrestrial solar-induced chlorophyll fluorescence from TanSat satellite显示文摘The first Chinese Carbon Dioxide Observation Satellite Mission(TanSat), which was launched on December 21, 2016, is intended to measure atmospheric CO_2 concentration.The high spectral resolution(0.044 nm) and high SNR(360 at 15.2 mW m^(-1) sr^(-1) nm^(-1)) measurements in the region of the O_2-A band of the Atmospheric Carbon dioxide Grating Spectroradiometer(AGCS) module onboard TanSat make it possible to retrieve solar-induced chlorophyll fluorescence(SIF) from TanSat observations at the global scale.This paper aims to explore the potential of the TanSat data for global SIF retrieval.A singular vector decomposition(SVD) statistical method was employed to retrieve SIF using radiance over a micro spectral window(~2 nm) around the Fe Fraunhofer lines(centered at 758.8 nm).The global SIF at 758.8 nm was successfully retrieved with a low residual error of 0.03 mW m^(-1) sr^(-1) nm^(-1).The results show that the spatial and temporal patterns of the retrieved SIF agree well with the global terrestrial vegetation pattern.The monthly SIF products retrieved from the TanSat data were compared with other remote sensing datasets, including OCO-2 SIF, MODIS NDVI, EVI and GPP.The overall consistency between TanSat and OCO-2 SIF products(R^2= 0.86) and the consistency of the spatial patterns and temporal variations between the TanSat SIF and MODIS vegetation indices and GPP enhance our confidence in the potential and feasibility of TanSat data for SIF retrieval.TanSat, therefore, provides a new opportunity for global sampling of SIF at fine spatial resolution(2 km × 2 km), thus improving photosynthesis observations from space. | Shanshan Du Liangyun Liu Xinjie Liu Xiao Zhang Xingying Zhang Yanmeng Bi Lianchong Zhang | 2018 | Science Bulletin2018，63，22： | 29 |
| 2 | Finer-Resolution Mapping of Global Land Cover: Recent Developments, Consistency Analysis, and Prospects显示文摘Land-cover mapping is one of the foundations of Earth science.As a result of the combined efforts of many scientists,numerous global land-cover(GLC)products with a resolution of 30 m have so far been generated.However,the increasing number of fineresolution GLC datasets is imposing additional workloads as it is necessary to confirm the quality of these datasets and check their suitability for user applications.To provide guidelines for users,in this study,the recent developments in currently available 30 m GLC products(including three GLC products and thematic products for four different land-cover types,i.e.,impervious surface,forest,cropland,and inland water)were first reviewed.Despite the great efforts toward improving mapping accuracy that there have been in recent decades,the current 30 m GLC products still suffer from having relatively low accuracies of between 46.0%and 88.9%for GlobeLand30-2010,57.71%and 80.36%for FROM_GLC-2015,and 65.59%and 84.33%for GLC_FCS30-2015.The reported accuracies for the global 30 m thematic maps vary from 67.86%to 95.1%for the eight impervious surface products that were reviewed,56.72%to 97.36%for the seven forest products,32.73%to 98.3%for the six cropland products,and 15.67%to 99.7%for the six inland water products.The consistency between the current GLC products was then examined.The GLC maps showed a good overall agreement in terms of spatial patterns but a limited agreement for some vegetation classes(such as shrub,tree,and grassland)in specific areas such as transition zones.Finally,the prospects for fine-resolution GLC mapping were also considered.With the rapid development of cloud computing platforms and big data,the Google Earth Engine(GEE)greatly facilitates the production of global fine-resolution land-cover maps by integrating multisource remote sensing datasets with advanced image processing and classification algorithms and powerful computing capability.The synergy between the spectral,spatial,and temporal features derived from multisource satellite datasets and stored in cloud computing platforms will definitely improve the classification accuracy and spatiotemporal resolution of fineresolution GLC products.In general,up to now,most land-cover maps have not been able to achieve the maximum(per class or overall)error of 5%–15%required by many applications.Therefore,more efforts are needed toward improving the accuracy of these GLC products,especially for classes for which the accuracy has so far been low(such as shrub,wetland,tundra,and grassland)and in terms of the overall quality of the maps. | Liangyun Liu Xiao Zhang Yuan Gao Xidong Chen Xie Shuai Jun Mi | 2021 | Journal of Remote Sensing2021，，1： | 9 |
| 3 | Effect of Fe, Si and Cooling Rate on the Formation of Fe-and Mn-rich Intermetallics in Al–5Mg–0.8Mn Alloy显示文摘The Fe-and Mn-rich intermetallics are of great effect on the mechanical properties of the AA5083 type alloy(Al–5Mg–0.8Mn). The effect of Fe, Si and cooling rate on the formation of the intermetallics were investigated by analyzing the microstructures of the alloys with different Fe and Si contents. The results indicated that increasing the Fe content resulted in the increase of the Al_6(Fe,Mn) phase in both amount and size. In the alloys with high Fe content, the platelet-like Al_6(Fe,Mn) compounds lined up and formed a band. Increasing the content of Si resulted in the increase of the Mg_2 Si phase which formed a network structure. Increasing the cooling rate significantly refined the intermetallics. However, increasing the cooling rate did not change the characteristic of the intermetallic compounds in the alloys with low or medium Si contents. For the alloys with high contents of Fe and Si under the condition of near-rapid cooling, the Fe- and Mn-rich intermetallic compound changed to the quaternary (Al)_15(Fe,Mn)_3Si phase and displayed a fine fish bone or Chinese script structure. The refinement of the intermetallics would allow higher tolerance of Fe and Si contents in the AA5083 alloy produced, for instance, via the continuous strip casting process. | Yulin Liu Lei Luo Chaofei Han Liangyun Ou Jijie Wang Chunzhong Liu | 2016 | Journal of Materials Science & Technology2016，32，4： | 7 |
| 4 | Effect of Direct Quenching on Microstructure and Mechanical Properties of a Wear-resistant Steel显示文摘A wear-resistant steel was hot rolled at the same finish temperature,and subsequently treated with conventional reheat quenching and tempering process(RQ&T) and direct quenching and tempering process(DQ&T),respectively.The effect of direct quenching on the microstructure and mechanical properties was investigated in detail by using optical microscope,transmission electron microscope and scanning electron microscope equipped with electron backscattered diffraction.The results showed that the microstructures of both the RQ and DQ specimens were complex constituents of lath martensite and lower bainite.Compared with the RQ specimen,the lower bainite content in DQ specimen was much higher.Furthermore,the bainite in the DQ specimen extended into and segmented the prior austenite grains,which can decrease martensite packet size.The proportion of high-angle boundary in the DQ specimen was higher than that in the RQ specimen,which may improve the impact toughness.The carbides in DQ&T specimen were much finer and distributed even dispersively because direct quenching can retain substantive defects which may provide more nucleation sites for carbide precipitation in the tempering process.Besides,the mechanical properties of DQ and DQ&T specimens were superior than those subjected to RQ and RQ&T processes,respectively. | Hongyu SONG Shunhu ZHANG Liangyun LAN Canming LI Haitao LIU Dewen ZHAO Guodong WANG | 2013 | Acta Metallurgica Sinica(English Letters)2013，26，4： | 7 |
| 5 | Effects of elevation on spring phenological sensitivity to temperature in Tibetan Plateau grasslands显示文摘Vegetation phenology is an important indicator of climate change impacts on the seasonal dynamics of the biosphere. However, little is known about the influence of elevation on spring phenological sensitivity to temperature in an alpine ecosystem. Based on remotely sensed land surface phenology and temperature data from 2001 to2010, this study investigated the rate of spring phenological change of the Tibetan Plateau(TP) grasslands in response to interannual temperature variations at different elevations. Results suggest that spring phenology in the TP grasslands exhibits a stronger response to changes in temperature at higher elevations than at lower ones. In particular, spring phenology advanced by 1–2 days in response to a 1 °C increase in May average temperature at elevations from 3,000 to 3,500 m, while the rate was up to8–9 days/°C at 5,000–5,500 m. Analysis using accumulated growing degree days(AGDD) from January 1through May 31 showed the same general trend with increased elevation associated with increased sensitivity(as measured by phenological change per unit of AGDDchange). Such temperature sensitivity gradients in the TP grasslands could be partly explained by the growth efficiency hypothesis which suggests that vegetation adapted to colder climates likely requires less heat energy for the onset of growing season and vice versa in warmer climates.Furthermore, accumulated growing degree days from January 1 to the greenup date were found to decrease with increasing elevations, which provided evidence to support the applicability of the growth efficiency hypothesis in an alpine grassland ecosystem. | Lingling Liu Liangyun Liu Liang Liang Alison Donnelly Isaac Park Mark D.Schwartz | 2014 | Chinese Science Bulletin2014，59，34： | 7 |
| 6 | Dynamic analysis of the Wenchuan Earthquake disaster and reconstruction with 3-year remote sensing data显示文摘Earth observation is an effective technique that plays an important role in earthquake damage reduction and reconstruction.This paper introduces the results of dynamic analysis on monitoring and assessing heavily impacted areas affected by the Wenchuan Earthquake using remote sensing data acquired in the past 3 years from 2008 to 2010.Immediately after the disaster on 12 May 2008,the Chinese Academy of Sciences launched a project entitled‘Wenchuan Earthquake Disasters Monitoring and Assessment Using Remote Sensing Technology.’More than 400 images from 17 satellites and 20.2TB airborne remote sensing data were acquired to facilitate quick monitoring and evaluation of severely damaged areas in 14 counties.Results of the image analyses were forwarded on a timely basis to assist with consultative service and decisionmaking support.In subsequent years,in order to monitor the process of environmental restoration and reconstruction,airborne optical remote sensing images covering most of the severely damaged areas were again acquired in May 2009 and April 2010.These images were analyzed and compared along with images from 2008.Results were useful in support of further work on environmental protection and reconstruction in earthquake-damaged areas.Three typical areas were selected for illustrative purposes including Tangjiashan Barrier Lake,Beichuan County,and counties of Yingxiu and the new Beichuan.These results well demonstrate the importance and effectiveness of the utility of earth observation for disaster mitigation and reconstruction. | Huadong Guo Liangyun Liu Liping Lei Yanhong Wu Liwei Li Bing Zhang Zhengli Zuo Zhen Li | 2010 | International Journal of Digital Earth2010，3，4： | 5 |
| 7 | Prospects for Solar-Induced Chlorophyll Fluorescence Remote Sensing from the SIFIS Payload Onboard the TECIS-1 Satellite显示文摘The importance of solar-induced chlorophyll fluorescence(SIF)to monitoring vegetation photosynthesis has attracted much attention from the ecological and remote sensing research communities.Space-borne SIF products have been obtained owing to the rapid development of atmospheric satellites in recent years.The SIF Imaging Spectrometer(SIFIS)is a payload onboard the upcoming Terrestrial Ecosystem Carbon Inventory Satellite(TECIS-1)that is specifically designed for SIF monitoring.We conducted an in situ experiment to evaluate the performance of SIFIS on spectral measurement and SIF retrieval through comparison to the commercial spectrometer QE Pro.Disregarding the spatiotemporal mismatch between the collected measurements of the two spectrometers,the radiance spectra obtained synchronously by SIFIS and QE Pro showed a high level of consistency.The SIF retrieval,normalized difference vegetation index(NDVI),and near-infrared radiance of vegetation(NIRvR)results for a push-broom image shows consistent spatial distributions over both vegetated and nonvegetated surfaces.A quantitative comparison was conducted by strictly filtering matching pixels.For the far-red band,a high correlation was obtained between the SIF retrieval performances of SIFIS and QE Pro with R^(2)=0:70 and RMSE=0:30mWm^(−2)sr^(−−1)nm^(−1).However,a relatively poor correlation was observed for the red band with an R^(2)value of 0.23 and an RMSE of 0.26 mWm^(−2)sr^(-−1)nm^(−1).Despite the large uncertainties associated with this experiment,the results indicate that TECIS-1 should offer a reliable SIF monitoring performance after its launch. | Shanshan Du Xinjie Liu Jidai Chen Liangyun Liu | 2022 | Journal of Remote Sensing2022，，1： | 3 |
| 8 | A New Global Solar-induced Chlorophyll Fluorescence(SIF)Data Product from TanSat Measurements显示文摘The Chinese Carbon Dioxide Observation Satellite Mission(TanSat)is the third satellite for global CO2 monitoring and is capable of detecting weak solar-induced chlorophyll fluorescence(SIF)signals with its advanced technical characteristics.Based on the Institute of Atmospheric Physics Carbon Dioxide Retrieval Algorithm for Satellite Remote Sensing(IAPCAS)platform,we successfully retrieved the TanSat global SIF product spanning the period of March 2017 to February 2018 with a physically based algorithm.This paper introduces the new TanSat SIF dataset and shows the global seasonal SIF maps.A brief comparison between the IAPCAS TanSat SIF product and the data-driven SVD(singular value decomposition)SIF product is also performed for follow-up algorithm optimization.The comparative results show that there are regional biases between the two SIF datasets and the linear correlations between them are above 0.73 for all seasons.The future SIF data product applications and requirements for SIF space observation are discussed. | Lu YAO Dongxu YANG Yi LIU Jing WANG Liangyun LIU Shanshan DU Zhaonan CAI Naimeng LU Daren LYU Maohua WANG Zengshan YIN | 2021 | Advances in Atmospheric Sciences2021，38，3： | 3 |
| 9 | Some Subsystems of a Lie Triple System Closely Related to Its Frattini Subsystem显示文摘The main purpose of the present paper is to give some properties of the Jacobson radical,the Frattini subsystem and c-ideals of a Lie triple system.Some further results concerning the Frattini subsystems of nilpotent and solvable Lie triple systems are obtained.Moreover,we develop initially c-ideals for a Lie triple system and make use of them to give some characterizations of a solvable Lie triple system. | Liangyun CHEN Dong LIU Xiaoning XU | 2013 | Chinese Annals of Mathematics,Series B2013，34，5： | 2 |
| 10 | Seasonal dynamic pattern analysis on global FPAR derived from AVHRR GIMMS NDVI显示文摘The purpose of this paper is to develop Advanced Very High Resolution Radiometer(AVHRR)Global Inventory Modelling and Mapping Studies(GIMMS)Normalised Difference Vegetation Index(NDVI;AVHRR GIMMS NDVI for short)based fraction of absorbed photosynthetically active radiation(FPAR)from 1982 to 2006 and focus on their seasonal and spatial patterns analysis.The available relationship between FPAR and NDVI was used to calculate FPAR values from 1982 to 2006 and validated by Moderate-resolution Imaging Spectroradiometer(MODIS)FPAR product.Then,the seasonal dynamic patterns were analysed,as well as the driving force of climatic factors.Results showed that there was an agreement between FPAR values from this study and those of the MODIS product in seasonal dynamic,and the spatial patterns of FPARvary with vegetation type distribution and seasonal cycles.The time series of average FPAR revealed a strong seasonal variation,regular periodic variations from January 1982 to December 2006,and opposite patterns between the Northern and Southern Hemispheres.Evergreen vegetation FPARvalues were close to 0.7.A clear single-peak curve was observed between 308N and 808N?an area covered by deciduous vegetation.In the Southern Hemisphere,the time series fluctuations of FPAR averaged by 0.78 latitude zones were not clear compared to those in the Northern Hemisphere.A significant positive correlation(PB0.01)was observed between the seasonal variation of temperature and precipitation and FPAR over most other global meteorological sites. | Dailiang Peng Bing Zhang Liangyun Liu Dongmei Chen Hongliang Fang Yong Hu | 2012 | International Journal of Digital Earth2012，5，5： | 2 |
| 11 | Specific patterns of XC02 observed by GOSAT during 2009-2016and assessed with model simulations over China显示文摘Spatiotemporal patterns of column-averaged dry air mole fraction of CO2(XCO2)have not been well characterized on a regional scale due to limitations in data availability and precision.This paper addresses these issues by examining such patterns in China using the long-term mapping XCO2 dataset(2009-2016)derived from the Greenhouse gases Observing SATellite(GOSAT).XCO2 simulations are also constructed using the high-resolution nested-grid GEOS-Chem model.The following results are found:Firstly,the correlation coefficient between the anthropogenic emissions and XCO2 spatial distribution is nearly zero in summer but up to 0.32 in autumn.Secondly,on average,XCO2 increases by 2.08 ppm every year from2010 to 2015,with a sharp increase of 2.6 ppm in 2013.Lastly,in the analysis of three typical regions,the GOSAT XCO2 time series is inbetter agreement with the GEOS-Chem simulation of XCO2 in the Taklimakan Desert region(the least difference with bias 0.65±0.78 ppm),compared with the northern urban agglomerationregion(-1.3±1.2 ppm)and the northeastern forest region(-1.4±1.4 ppm).The results are likely attributable to uncertainty in both the satellite-retrieved XCO2 data and the model simulation data. | Nian BIE Liping LEI Zhonghua HE Zhaocheng ZENG Liangyun LIU Bing ZHANG Bofeng CAI | 2020 | Science China Earth Sciences2020，63，3： | 2 |
| 12 | Estimating winter wheat plant water content using red edge pa- rameters 显示文摘 | LIU LIANGYUN WANG JIHUA HUANG WENJIANG | 2004 | International Journal of Remote Sensing2004，25，17： | 1 |
| 13 | Analysis of the changes of vegetation coverage of western Beijing mountainous areas using remote sensing and GIS显示文摘 | Liu Liangyun Jing Xia Wang Jihua | 2009 | Environ Monit Assess2009，153，： | 1 |
| 14 | Polynomial analysis of canopy spectra and biochemical component content inversion显示文摘A polynomial expression model was developed in this paper to describe directional canopy spectra, and the decomposition of the polynomial expression was used as a tool for re-trieving biochemical component content from canopy multi-angle spectra. First, the basic formula of the polynomial expression was introduced and the physical meaning of its terms and coeffi-cients was discussed. Based on this analysis, a complete polynomial expression model and its decomposition method were given. By decomposing the canopy spectra simulated with SAILH model, it shows that the polynomial expression can not only fit well the canopy spectra, but also show the contribution of every order scattering to the whole reflectance. Taking the first scattering coefficients a10 and a01 for example, the test results show that the polynomial coefficients reflect very well the hot spot phenomenon and the effects of viewing angles, LAI and leaf inclination angle on canopy spectra. By coupling the polynomial expression with leaf model PROSPECT, a canopy biochemical component content inversion model was given. In the simulated test, the canopy multi-angle spectra were simulated by two different models, SAILH and 4-SCALE re-spectively, then the biochemical component content was retrieved by inverting the coupled polynomial expression + PROSPECT model. Results of the simulated test are promising, and when applying the algorithm to measured corn canopy multi-angle spectra, we also get relatively accurate chlorophyll content. It shows that the polynomial analysis provides a new method to get biochemical component content independent of any specific canopy model. | YAN Chunyan1, LIU Qiang1, NIU Zheng1, WANG Jihua2, HUANG Wenjiang2 & LIU Liangyun 2 1. State Key Laboratory of Remote Sensing Science, Jointly Sponsored by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University, Beijing 100101, China 2. National Engineering Research Center for Information Technology in Agriculture, Beijing 100089, China | 2005 | Science China Earth Sciences2005，48，10： | 1 |
| 15 | Estimating biophysical and biochemical parameters and yield of winterwheat based on land sat tm images显示文摘 | Yansong Bao Liangyun Liu Jihua Wang | 2008 | IEEE Transaction on Pattern Analysis and Machine Intelligence2008，7，2： | 1 |
| 16 | Identification of yellow rust in wheat using in-situ spectral reflectance measurements and airborne hyperspectral imaging显示文摘 | Wenjiang Huang David W. Lamb Zheng Niu Yongjiang Zhang Liangyun Liu Jihua Wang | 2007 | Precision Agriculture (-)2007，，4： | 1 |
| 17 | Predicting grain protein content of winter wheat using remote sensing data based on nitrogen status and water stress显示文摘 | Chunjiang Zhao Liangyun Liu Jihua Wang | 2005 | International Journal of Applied Earth Observation and Geoinformation2005，7，1： | 1 |
| 18 | Uncertainty Analysis for NDVI Using the Physical Models显示文摘 | JING juanjuan LIU liangyun WANG jihua | 2004 | IGARSS2004，6，： | 1 |
| 19 | Predicting winter wheat condition,grain yield and protein content using Multi-temporal EnviSat-ASAR and Landsat TM satellite images显示文摘 | Liangyun Liu Jihua Wang Yansong Bao | 2006 | International Journal of Remote Sensing2006，27，4： | 1 |
| 20 | Characteristics and drivers of global NDVI-based FPAR from 1982 to 2006显示文摘 | Peng Dailiang Zhang Bing Liu Liangyun Fang Hongliang Chen Dongmei Hu Yong Liu Lingling | 2012 | EN2012，，3： | 1 |
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