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An automatic extraction method for individual tree crowns based on self-adaptive mutual information and tile computing

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International Journal of Digital Earth 2015年第6期8卷 495-516页

作者： Ying Bao Qingjiu Tian Min Chen Hui Lin International Institute for Earth System science Nanjing UniversityNanjingPR China jiangsu provincial key Laboratory of geographic information science and technology Nanjing UniversityNanjingPR China Institute of Space and Earth information science The Chinese University of Hong KongShatinHong KongPR China Shenzhen Research Institute The Chinese University of Hong KongShenzhenPR China Department of Geography and Resource Management The Chinese University of Hong KongShatinHong KongPR China

Forest data acquisition,which is of crucial importance for modeling global biogeochemical cycles and climate,makes a contribution to building the ecological Digital Earth(DE).Due to the complex calculations and large volumes of data associated with high-resolution images of large areas,accurate and effective extraction of individual tree crowns remains challenging.In this study,two GeoEye-1 panchromatic images of Beihai and Ningbo in China with areas of 5 and 25 km2,respectively,were used as experimental data to establish a novel method for the automatic extraction of individual tree crowns based on a self-adaptive mutual information(SMI)algorithm and tile computing technology(SMI-TCT).To evaluate the performance of the algorithm,four commonly used algorithms were also applied to extract the individual tree crowns.The overall accuracy of the proposed method for the two experimental areas was superior to that of the four other algorithms,with maximum extraction accuracies of 85.7%and 63.8%.Moreover,the results also indicated that the novel method was suitable for individual tree crowns extraction in sizeable areas because of the multithread parallel computing technology.

关键词： individual tree crowns GeoEye-1 automatic extraction tile computing mutual information

Changes of net primary productivity in China during recent 11 years detected using an ecological model driven by MODIS data

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Frontiers of Earth science 2013年第1期7卷 112-127页

作者： Yibo LIU Weimin JU Honglin HE Shaoqiang WANG Rui SUN Yuandong ZHANG jiangsu provincial key Laboratory of geographic information science and technology Nanjing University Nanjing 210093 China International Institute for Earth System science Nanjing University Nanjing 210093 China key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China State key Laboratory of Remote Sensing science Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing Applications of Chinese Academy of Sciences Beijing 100875 China key Laboratory of Forest Ecology and Environment State Forestry Administration Institute of Forest Ecology Environment and Protection Chinese Academy of Forestry Beijing 100091 China

Net primary productivity （NPP） is an important component of the terrestrial carbon cycle. Accurately mapping the spatial-temporal variations of NPP in China is crucial for global carbon cycling study. In this study the process-based Boreal Ecosystem Productivity Simulator （BEPS） was employed to study the changes of NPP in China＇s ecosystems for the period from 2000 to 2010. The BEPS model was first validated using gross primary productivity （GPP） measured at typical flux sites and forest NPP measured at different regions. Then it was driven with leaf area index （LAI） inversed from the Moderate Resolution Imaging Spectroradiometer （MODIS） reflec- tance and land cover products and meteorological data interpolated from observations at753 national basic meteorological stations to simulate NPP at daily time steps and a spatial resolution of 500m from January 1, 2000 to December 31, 2010. Validations show that BEPS is able to capture the seasonal variations of tower-based GPP and the spatial variability of forest NPP in different regions of China. Estimated national total of annual NPP varied from 2.63 to 2.84Pg C.yr-1, averaging 2.74Pg C.yr-1 during the study period. Simulated terrestrial NPP shows spatial patterns decreasing from the east to the west and from the south to the north, in association with land cover types and climate. South-west China makes the largest contribution to the national total of NPP while NPP in the North-west account for only 3.97% of the national total. During the recent 11 years, the temporal changes of NPP were heterogamous. NPP increased in 63.8% of China＇s landmass, mainly in areas north of the Yangtze River and decreased in most areas of southern China, owing to the low temperature freezing in early 2008 and the severe drought in late 2009.

关键词： temporal and spatial variations NPP remotesensing MODIS data BEPS model

Assessment and adjustment of sea surface salinity products from Aquarius in the southeast Indian Ocean based on in situ measurement and My Ocean modeled data

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Acta Oceanologica Sinica 2016年第3期35卷 54-62页

作者： XIA Shenzhen KE Changqing ZHOU Xiaobing ZHANG Jie jiangsu provincial key Laboratory of geographic information science and technology Nanjing UniversityNanjing 210023China Collaborative Innovation Center of South China Sea Studies Nanjing 210023China Collaborative Innovation Center of Novel Software technology and Industrialization Nanjing 210023China Department of Geophysical Engineering Montana Tech of the University of MontanaButteMT 59701USA The First Institute of Oceanography State Oceanic AdministrationQingdao 266061China

The in situ sea surface salinity（SSS） measurements from a scientific cruise to the western zone of the southeast Indian Ocean covering 30°-60°S, 80°-120°E are used to assess the SSS retrieved from Aquarius（Aquarius SSS）.Wind speed and sea surface temperature（SST） affect the SSS estimates based on passive microwave radiation within the mid- to low-latitude southeast Indian Ocean. The relationships among the in situ, Aquarius SSS and wind-SST corrections are used to adjust the Aquarius SSS. The adjusted Aquarius SSS are compared with the SSS data from My Ocean model. Results show that：（1） Before adjustment： compared with My Ocean SSS, the Aquarius SSS in most of the sea areas is higher; but lower in the low-temperature sea areas located at the south of 55°S and west of 98°E. The Aquarius SSS is generally higher by 0.42 on average for the southeast Indian Ocean.（2） After adjustment： the adjustment greatly counteracts the impact of high wind speeds and improves the overall accuracy of the retrieved salinity（the mean absolute error of the Zonal mean is improved by 0.06, and the mean error is-0.05 compared with My Ocean SSS）. Near the latitude 42°S, the adjusted SSS is well consistent with the My Ocean and the difference is approximately 0.004.

关键词： Aquarius sea surface salinity（SSS） in situ SSS My Ocean comparison analysis southeast Indian Ocean

基于MODIS数据的南极半岛北部冰架表面流速估算（英文）

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地理学报：英文版 2016年第2期26卷 243-256页

作者：陈军柯长青周小兵邵珠德李澜宇 jiangsu provincial key Laboratory of geographic information science and technology Nanjing University key Laboratory for Satellite Mapping technology and Applications of State Administration of Surveying Mapping and Geoinformation of ChinaNanjing University Department of Geophysical Engineering Montana Tech of the University of Montana

The ice shelves in the northern Antarctic Peninsula are highly sensitive to variations of temperature and have therefore served as indicators of global warming. In this study,we estimate the velocities of the ice shelves in the northern Antarctic Peninsula using co-registration of optically sensed images and correlation module(COSI-Corr) in the Environment for Visualizing Images(ENVI) based on Moderate Resolution Imaging Spectroradiometer(MODIS) images during 2000–2012,from which we conclude that the ice flow directions generally match the peninsulas pattern and the crevasse,ice flows mainly eastward into the Weddell Sea. The spatial pattern of velocity field exhibits an increasing trend from the western grounding line to the maximum at the middle part of the ice shelf front on Larsen C with a velocity of approximately 700 ma–1,and the velocity field shows relatively higher values in its southerly neighboring ice shelf(e.g. Smith Inlet). Additionally,ice flows are relatively quicker in the outer part of the ice shelf than in the inner parts. Temporal changes in surface velocities show a continuous increase from 2000 to 2012. It is worth noting that,the acceleration rate during 2000–2009 is relatively higher than that during 2009–2012,while the ice movement on the southern Larsen C and Smith Inlet shows a deceleration from 2009 to 2012.

关键词： MODIS数据表面速度南极半岛冰架中分辨率成像光谱辐射计估计图像配准 Smith

Vegetation recovery trends under dual dominance of climate change and anthropogenic factors in the severely damaged areas of the Wenchuan earthquake

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Journal of Mountain science 2022年第11期19卷 3131-3147页

作者： WANG Qian WANG Ze-gen YONG Zhi-wei ZHAO Kai XIONG Jun-nan DU Xue-mei Zhao Yang School of Geoscience and technology Southwest Petroleum UniversityChengdu 610500China Applied Geology Research Center of China Geological Survey Chengdu 610036China School of Civil Engineering and Geomatics Southwest Petroleum UniversityChengdu 610500China State key Laboratory of Resources and Environmental information System Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China

The occurrence of the Wenchuan earthquake caused the degradation of regional ecosystems,including vegetation destruction.However,the post-seismic vegetation recovery and its driving forces on the spatial-temporal scale are still vague,especially in the severely damaged areas(including Wenchuan,Beichuan,Mianzhu,Shifang,Qingchuan,Maoxian,Anzhou,Dujiangyan,Pingwu and Pengzhou).Here,we detected vegetation recovery in the severely damaged areas by using Ensemble Empirical Mode Decomposition(EEMD)to analyze the time series characteristics of the Enhanced Vegetation Index(EVI),and explored the driving effects of climate,land use types,nighttime light,water system,slope,and clay content on vegetation recovery based on geographically and Temporally Weighted Regression(GTWR)model.The results indicated that the post-seismic vegetation recovery rate increased rapidly(acceleration>0)but slowed down after 2013.And the areas of best vegetation recovery(EVI increments>0.1)were distributed in the north of the study area,the Minjiang River Basin,and front fault and central fault of the Longmenshan Fault Zone.While the areas with the worst vegetation recovery(EVI increments0),but the impacts weakened after the earthquake,possibly due to the increase of secondary disasters induced by precipitation and the rise in maximum temperature.The impact of cultivated land on vegetation recovery was mostly positive(regression coefficients>0),which may be related to the implementation of the Grain for Green Project.The nighttime light inhibited vegetation recovery(regression coefficients<0),which could be closely associated with urbanization.The results indicated that more attention should be paid to the nonlinear variations of post-earthquake vegetation recovery trends

关键词： Vegetation recovery Enhanced Vegetation Index Ensemble empirical mode decomposition geographically and Temporally Weighted Regression

Strong controls of daily minimum temperature on the autumn photosynthetic phenology of subtropical vegetation in China

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Forest Ecosystems 2021年第3期8卷 413-424页

作者： Peixin Ren Zelin Liu Xiaolu Zhou Changhui Peng Jingfeng Xiao Songhan Wang Xing Li Peng Li College of geographic science Hunan Normal UniversityChangsha 410081China Department of Biology sciences Institute of Environment SciencesUniversity of Quebec at MontrealC.P.8888Succ.Centre-VilleMontreal H3C 3P8Canada Earth Systems Research Center Institute for the Study of EarthOceansand SpaceUniversity of New HampshireDurhamNH 03824USA International Institute for Earth System sciences Nanjing UniversityNanjing 210023China jiangsu provincial key Laboratory of geographic information technology Key Laboratory for Land Satellite Remote Sensing Applications of Ministry of Natural ResourcesSchool of Geography and Ocean ScienceNanjing UniversityNanjing 210023China

Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions.Results:Using satellite solar-induced chlorophyll fluorescence(SIF)and MODIS enhanced vegetation index(EVI)data,we applied two methods to evaluate temporal and spatial patterns of the end of the growing season(EGS)in subtropical vegetation in China,and analyze the dependence of EGS on preseason maximum and minimum temperatures as well as cumulative precipitation.Our results indicated that the averaged EGS derived from the SIF and EVI based on the two methods(dynamic threshold method and derivative method)was later than that derived from gross primary productivity(GPP)based on the eddy covariance technique,and the time-lag for EGSsif and EGSevi was approximately 2 weeks and 4 weeks,respectively.We found that EGS was positively correlated with preseason minimum temperature and cumulative precipitation(accounting for more than 73%and 62%of the study areas,respectively),but negatively correlated with preseason maximum temperature(accounting for more than 59%of the study areas).In addition,EGS was more sensitive to the changes in the preseason minimum temperature than to other climatic factors,and an increase in the preseason minimum temperature significantly delayed the EGS in evergreen forests,shrub and grassland.Conclusions:Our results indicated that the SIF outperformed traditional vegetation indices in capturing the autumn photosynthetic phenology of evergreen forest in the subtropical region of China.We found that minimum temperature plays a significant role in determining autumn photosynthetic phenology in the study region.These findings contribute to improving our understanding of the response of the EGS to climate change in subtropical vegetation of China,and provide a new perspective for accurately evaluating the role played by evergreen vegetation in the regional carbon budget.

关键词： Carbon cycle Evergreen vegetation Plant phenology Solar-induced Fluorescence Climate change MODIS Eddy covariance

Strength of the North African monsoon in the Last Interglacial and under future warming

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Atmospheric and Oceanic science Letters 2023年第3期16卷 20-26页

作者： Jiazhi He Weiyi Sun Jing Wang Bin Wang Jian Liu key Laboratory for Virtual geographic Environment Ministry of EducationState Key Laboratory Cultivation Base of Geographical Environment Evolution of Jiangsu ProvinceJiangsu Center for Collaborative Innovation in Geographical Information Resource Development and ApplicationSchool of Geography ScienceNanjing Normal UniversityNanjingChina Department of Atmospheric sciences and AtmosphereOcean Research Center University of Hawaii at ManoaHonoluluHIUA jiangsu provincial key Laboratory for Numerical Simulation of Large Scale Complex Systems School of Mathematical ScienceNanjing Normal UniversityNanjingChina Open Studioforthe Simulationof Ocean-Climate-Isotope Qingdao National Laboratoryfor Marine Science and TechnologyQingdaoChina

与人为强迫引起的全球变暖相比,末次间冰期是轨道强迫引起的过去80万年来最暖的一个间冰期,但鲜有人研究末次间冰期中北非季风的响应.因此,本文基于CMIP6多模式模拟结果对比研究了末次间冰期和SSP5-8.5情景下北非季风的响应,发现末次间... 详细信息

与人为强迫引起的全球变暖相比,末次间冰期是轨道强迫引起的过去80万年来最暖的一个间冰期,但鲜有人研究末次间冰期中北非季风的响应.因此,本文基于CMIP6多模式模拟结果对比研究了末次间冰期和SSP5-8.5情景下北非季风的响应,发现末次间冰期下北非季风平均降水及其降水变率均远大于SSP5-8.5情景下的结果.轨道强迫导致的北大西洋暖于南大西洋增加了北非季风环流和平均降水,同时,南北大西洋海温梯度变化通过增强热带北大西洋的海气相互作用增大了海温梯度和撒哈拉低压的变率,从而增强了北非季风降水变率.

关键词：北非季风降水变率末次间冰期全球变暖

Altered trends in carbon uptake in China's terrestrial ecosystems under the enhanced summer monsoon and warming hiatus

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National science Review 2019年第3期6卷 505-514页

作者： Honglin He Shaoqiang Wang Li Zhang Junbang Wang Xiaoli Ren Lei Zhou Shilong Piao Hao Yan Weimin Ju Fengxue Gu Shiyong Yu Yuanhe Yang Miaomiao Wang Zhongen Niu Rong Ge Huimin Yan Mei Huang Guoyi Zhou Yongfei Bai Zongqiang Xie Zhiyao Tang Bingfang Wu Leiming Zhang Nianpeng He Qiufeng Wang Guirui Yu University of Chinese Academy of sciences key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems South China Botanical Garden Chinese Academy of Sciences Department of Ecology College of Urban and Environmental Science Key Laboratory for Earth Surface Processes of the Ministry of Education Peking University Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences Synthesis Research Center of China's Ecosystem Research Network Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences College of Resources and Environment University of Chinese Academy of Sciences Sino-French Institute for Earth System science College of Urban and Environment Sciences Peking University key Laboratory of Alpine Ecology and Biodiversity Institute of Tibetan Plateau Research CAS Center for Excellence in Tibetan Plateau Earth Science Chinese Academy of Sciences National Meteorological Center China Meteorological Administration International Institute for Earth System science and jiangsu provincial key Laboratory of geographic information science and technology Nanjing University key Laboratory of Dryland Agriculture MOA Institute of Environment and Sustainable Development in Agriculture Chinese Academy of Agricultural Sciences School of Geography Geomatics and Planning Jiangsu Normal University State key Laboratory of Vegetation and Environmental Change Institute of Botany Chinese Academy of Sciences

The carbon budgets in terrestrial ecosystems in China are strongly coupled with climate changes. Over the past decade, China has experienced dramatic climate changes characterized by enhanced summer monsoon and decelerated warming. However, the changes in the trends of terrestrial net ecosystem production(NEP) in China under climate changes are not well documented. Here, we used three ecosystem models to simulate the spatiotemporal variations in China’s NEP during 1982–2010 and quantify the contribution of the strengthened summer monsoon and warming hiatus to the NEP variations in four distinct climatic regions of the country. Our results revealed a decadal-scale shift in NEP from a downtrend of–5.95 TgC/yr~2(reduced sink) during 1982–2000 to an uptrend of 14.22 TgC/yr~2(enhanced sink) during 2000–10. This shift was essentially induced by the strengthened summer monsoon, which stimulated carbon uptake, and the warming hiatus, which lessened the decrease in the NEP trend. Compared to the contribution of 56.3% by the climate effect, atmospheric CO2concentration and nitrogen deposition had relatively small contributions(8.6 and 11.3%, respectively) to the shift. In conclusion, within the context of the global-warming hiatus, the strengthening of the summer monsoon is a critical climate factor that enhances carbon uptake in China due to the asymmetric response of photosynthesis and respiration. Our study not only revealed the shift in ecosystem carbon sequestration in China in recent decades, but also provides some insight for understanding ecosystem carbon dynamics in other monsoonal areas.

关键词： climate change Asian summer monsoon warming hiatus biogeochemical modeling ecosystem carbon dynamics

Uncertainty analysis of cross-calibration for HJ-1 CCD camera

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Chinese science Bulletin 2013年第7期58卷 713-723页

作者： WANG Zuo XIAO PengFeng GU XingFa FENG XueZhi LI XiaoYing GAO HaiLiang LI Hui LIN JinTang ZHANG XueLiang jiangsu provincial key Laboratory of geographic information science and technology Nanjing University Department of geographic information science Nanjing University 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 Department of Spatial information science and Engineering Xiamen University of Technology Department of Geography science Minjiang University

Radiometric calibration of sensor is the basis of quantitative remote sensing,and uncertainty analysis is critical to ensure the accuracy of cross-calibration.Therefore,firstly,cross-calibration formulas were improved by redefining calibration coefficient and spectral band matching factor.In these formulas,cci was redefined as the calibration coefficient of normalized apparent reflectance,and spectral band matching factor as the ratio of normalized apparent reflectance.Secondly,based on the contrast of ideal and actual conditions in cross-calibration,8 sources of cross-calibration uncertainty were proposed:calibration uncertainty of standard sensor;pixel matching uncertainty;spectral band matching factor uncertainty caused by site altitude setting error,atmospheric parameters setting error,surface spectrum source,surface bidirectional reflectance characteristic,and error of atmospheric radiative transfer model;and uncertainty caused by other factors which were not considered.Finally,the contribution of each uncertainty was further analyzed and discussed for the HJ-1 CCD camera.The results provide many valuable references for evaluating the feasibility of alternative cross-calibration measurements.

关键词：校准系数 CCD相机不确定度分析不确定性分析表观反射率传感器校准辐射传输模型交叉定标