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Relationship Between Urban Road Traffic Characteristics and Road Grade Based on a Time Series Clustering Model： A Case Study in Nanjing, China

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Chinese geographical science 2018年第6期28卷 1048-1060页

作者： WANG Jiechen WU Jiayi NI Jianhua CHEN Jie XI Changbai Department of geographic information science Nanjing University Nanjing 210023 China jiangsu provincial key Laboratory of geographic information science and technology Nanjing 210023 China jiangsu Center for Collaborative Innovation in geographical information Resource Development and Application Nanjing 210023 China

With the increasing number of vehicles in large-and medium-sized cities challenges in urban traffic management, control, and road planning are being faced. Taxi GPS trajectory data is a novel data source that can be used to study the potential dynamic traffic characteristics of urban roads, and thus identify locations that show a notable lack of road planning. Considering that road traffic characteristics on their own are insufficient for a comprehensive understanding of urban traffic, we develop a road traffic characteristic time series clustering model to analyze the relationship between urban road traffic characteristics and road grade based on existing taxi trajectory data. We select the main urban area of Nanjing as our study area and use the taxi trajectory data of a single month for evaluating our method. The experiments show that the clustering model exhibit good performance and can be successfully used for road traffic characteristic classification. Moreover, we analyze the correlation between traffic characteristics and road grade to identify road segments with planning designs that do not match the actual traffic demands.

关键词：道路等级道路交通聚类模型特征时间特征和城市南京案例

Analysis of jiangsu Tidal Flats Reclamation from 1974 to 2012 Using Remote Sensing

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China Ocean Engineering 2015年第1期29卷 143-154页

作者：赵赛帅刘永学李满春孙超周旻曦张荷霞 jiangsu provincial key Laboratory of geographic information science and technology Nanjing University Collaborative Innovation Center for the South China Sea Studies Department of Geographic Information ScienceNanjing University jiangsu Center for Collaborative Innovation in geographical information Resource Development and Application Nanjing University

jiangsu has the most abundant tidal flat resources among China＇s coastal provinces. To ease the conflict between the growing population and shrinking usable land and to promote regional sustainable development, large-scale coastal reclamation development activities have been performed in jiangsu Province since 1949. The present study has integrated multi-source remote sensing images during 1974 to 2012 by using a Multi-point Fast Marching Method （MFMM） to extract the jiangsu coastal reclamation areas for different time periods. The temporal and spatial patterns of the extent and elevation of the reclamation areas were analysed in order to determine the unused potential for future reclamation. It will provide information necessary to support the development and construction of tidal flats in jiangsu. Results show that：（1） the reclaimed tidal fiats along the jiangsu coast cover more than 19.86×10^4 hm^2, of which 13.97×10^4 hm^2 is located in Yancheng, 4.84×10^4 hm^2 in Nantong, and 1.05×10^4 hm^2 in Lianyungang; （2） the average elevation of the reclaimed jiangsu tidal flats has gradually decreased over the last 40 years, while those in Dongtai and Rudong have showed particularly accelerated decrease since the 1990s; and （3） in 2012, very few unused tidal flats two meters above the sea level are left along the jiangsu coast, and mainly concentrated in Yancheng. As there are still reserving some coastal land resources between 0-2 m, providing us with a potential for future development. All of these findings may be useful for researchers and local authorities for the development and utilization of tidal flat resources in jiangsu.

关键词： tidalflats remote sensing jiangsu coast developmentpotential reclamation

Spatial-temporal variations of natural suitability of human settlement environment in the Three Gorges Reservoir Area A case study in Fengjie County,China

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Frontiers of Earth science 2019年第1期13卷 1-17页

作者： Jieqiong LUO Tinggang ZHOU Peijun DU Zhigang XU key Laboratory for Satellite Mapping technology and Applications of State Administration of Surveying Mapping and Geoinformation of China Nanjing UniversityNanjing 210023China Jiangsu Provincial Key Labomtory of Geographic Information Science and Technology Nanjing UniversityNanjing 210023China jiangsu Center for CoUabomtive Innovation in geographical information Resource Development and Application Nanjing 210023China School of geographical sciences Southwest UniversityChongqing 400715China key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education) Chongqing 400715China

With rapid environmental degeneration and socio-economie development,the human settlement environment (HSE)has experienced dramatic changes and attracted attention from different communities.Consequently,the spatial-temporal evaluation of natural suitability of the human settlement environment (NSHSE)has become essential for understanding the patterns and dynamics of HSE,and for coordinating sustainable development among regional populations,resources,and environments.This study aims to explore the spatialtemporal evolution of NSHSE patterns in 1997,2005,and 2009 in Fengjie County near the Three Gorges Reservoir Area (TGRA).A spatially weighted NSHSE model was established by integrating multi-source data (e.g.,census data,meteorological data,remote sensing images,DEM data,and GIS data)into one framework,where the Ordinary Least Squares (OLS)linear regression model was applied to calculate the weights of indices in the NSHSE model.Results show that the trend of natural suitability has been first downward and then upward, which is evidenced by the disparity of NSHSE existing in the south,north,and central areas of Fengjie County. Results also reveal clustered NSHSE patterns for all 30 townships.Meanwhile,NSHSE has significant influence on population distribution,and 71.49% of the total population is living in moderate and high suitable districts.

关键词： natural suitability of human settlement environment ordinary least squares model global and local spatial autocorrelation analyses Three Gorges Reservoir Area (TGRA) Fengjie Cotmty

Aerial observations of sea ice and melt ponds near the North Pole during CHINARE2010

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Acta Oceanologica Sinica 2017年第1期36卷 64-72页

作者： LI Lanyu KE Changqing XIE Hongjie LEI Ruibo TAO Anqi jiangsu provincial key Laboratory of geographic information science and technology Nanjing University Department of Geological sciences University of Texas at San Antonio Polar Research Institute of China State Oceanic Administration

An aerial photography has been used to provide validation data on sea ice near the North Pole where most polar orbiting satellites cannot cover. This kind of data can also be used as a supplement for missing data and for reducing the uncertainty of data interpolation. The aerial photos are analyzed near the North Pole collected during the Chinese national arctic research expedition in the summer of 2010（CHINARE2010）. The result shows that the average fraction of open water increases from the ice camp at approximately 87°N to the North Pole, resulting in the decrease in the sea ice. The average sea ice concentration is only 62.0% for the two flights（16 and 19 August 2010）. The average albedo（0.42） estimated from the area ratios among snow-covered ice,melt pond and water is slightly lower than the 0.49 of HOTRAX 2005. The data on 19 August 2010 shows that the albedo decreases from the ice camp at approximately 87°N to the North Pole, primarily due to the decrease in the fraction of snow-covered ice and the increase in fractions of melt-pond and open-water. The ice concentration from the aerial photos and AMSR-E（The Advanced Microwave Scanning Radiometer-Earth Observing System） images at 87.0°–87.5°N exhibits similar spatial patterns, although the AMSR-E concentration is approximately 18.0%（on average） higher than aerial photos. This can be attributed to the 6.25 km resolution of AMSR-E, which cannot separate melt ponds/submerged ice from ice and cannot detect the small leads between floes. Thus, the aerial photos would play an important role in providing high-resolution independent estimates of the ice concentration and the fraction of melt pond cover to validate and/or supplement space-borne remote sensing products near the North Pole.

关键词： sea ice melt pond albedo concentration aerial observation North Pole

Ensemble projections of climate and streamflow in a typical basin of semi-arid steppes in Mongolian Plateau of 2021-2100

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Advances in Climate Change Research 2024年第2期15卷 230-243页

作者： Hang PAN Jian-Ping TANG Liang CHENG Man-Chun LI jiangsu provincial key Laboratory of geographic information science and technology Nanjing UniversityNanjing 210023China School of Geography and Ocean science Nanjing UniversityNanjing 210023China key Laboratory of Mesoscale Severe Weather/Ministry of Education Nanjing UniversityNanjing 210023China School of Atmospheric sciences Nanjing UniversityNanjing 210023China

The Kherlen River is the main water source for Hulun Lake,the largest lake in northern China.Due to reduced inflow from the Kherlen River,Hulun Lake experienced rapid shrinkage at the beginning of the 21st century,posing a serious threat to the ecological security of northern China.However,there is still a significant lack of projections regarding future climate change and its hydrological response in the Kherlen River basin.This study analyzed the projected climate and streamflow changes in the Kherlen River basin,a vital yet vulnerable international semi-arid steppes type basin.A combination of multi-model ensemble projection techniques,and the soil and water assessment tool(SWAT)model was employed to examine the spatio-temporal changes in precipitation,temperature,streamflow,and the associated uncertainties in the basin.The temperature(an increase of 1.84-6.42℃)and the precipitation(an increase of 15.0-46.0 mm)of Kherlen River basin are projected to increase by 2100,leading to a rise in streamflow(1.08-4.78 m^(3) s^(-1)).The upstream of the Kherlen River exhibits remarkable increasing trends in precipitation,which has a dominant influence on streamflow of Kherlen River.Noteworthy increases in streamflow are observed in April,August,September,and October compared to the reference period(1971-2000).These findings suggest a partial alleviation of water scarcity in the Kherlen River,but also an increased likelihood of hydrological extreme events.The projected temperature increase in the Kherlen River basin exhibits the smallest uncertainty,while more pronounced uncertainties are found in precipitation and streamflow.The spread among the results of CMIP6 models is greater than that of CMIP5 models,with lower signal-to-noise ratio(SNR)values for temperature,precipitation,and streamflow.

关键词： Climate change Flow projection Uncertainty SWAT Mongolian Plateau

Improvement of ecological geographic regionalization based on remote sensing and canonical correspondence analysis： A case study in China

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science China Earth sciences 2016年第9期59卷 1745-1753页

作者： JIN JiaXin WANG Ying JIANG Hong KONG Yan LU XueHe ZHANG XiuYing jiangsu provincial key Laboratory of geographic information science and technology Nanjing University Nanjing 210023 China International Institute for Earth System science Nanjing University Nanjing 210023 China information Center of Urban Planning Wuxi 214072 China

Ecological geographic regions, also called eco-regions, can be used to divide a remotely sensed image, which is helpful for reducing the complexity of land cover types within eco-regions and for improving the classification accuracy of land cover. In this case study in China, we improved a method of ecological geographic regionalization that is more suitable for remote sensing mapping of regional land cover, and we obtained new eco-regions. The canonical correspondence analysis(CCA) and k-means clustering were adopted in the ecological geographic regionalization using both seasonal remotely-sensed vegetation information and environmental data including climate, elevation and soil features. Our results show that the combination of seasonal vegetation information and the CCA performed well in the selection of the dominant environmental factor of the biogeographic pattern, and it can be used as regionalization indicators of eco-regions. We found that thermal factors are the most important driving forces of the biogeographic pattern in China, which followed by moisture factors. Two global land cover products(MODIS MCD12C1 and Glob Cover) were used to assess our eco-regions. The results show that our eco-regions performed better than that of a previous study regarding the complexity of land cover types, such as in the number of types and the proportional area of the major/secondary type. These results indicate that the method of ecological geographic regionalization, which is based on environmental factors associated with seasonal vegetation features, is effective for reducing the regional complexity of land cover.

关键词：生态地理区划典范对应分析遥感图像中国案例土地覆盖类型生态区域生态地理区域

Water storage changes in the North China Plain from 2004 to 2019

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science China(Technological sciences) 2023年第7期66卷 2036-2046页

作者： CHEN MinLan XU YuYue PAN Hang WANG LuHan School of Geography and Ocean science Nanjing UniversityNanjing 210023China jiangsu provincial key Laboratory of geographic information science and technology Nanjing UniversityNanjing 210023China Frontiers science Center for Critical Earth Material Cycling Nanjing UniversityNanjing 210023China National Earth System science Data Center National Science and Technology Infrastructure of ChinaBeijing 100101China

In the past few decades,the irrational use of water resources has resulted in many issues such as land subsidence in the North China Plain(NCP),hindering its socio-economic development.An accurate understanding of water resource changes is important for the allocation of water resources in the NCP.In this study,we employed Gravity Recovery and Climate Experiment(GRACE) satellite data to monitor the total water storage(TWS) change in the NCP during 2004–2019.Evapotranspiration,precipitation,and runoff during 2004–2019 were sequentially examined,using the water balance formula(WBF),to retrieve TWS change.Furthermore,the soil moisture,snow water equivalent,and canopy water storage from the Global Land Data Assimilation System were used to calculate the natural component of the TWS variations.A comparison of these results revealed the drivers of the changes in water resources.The results showed that:(1) overall TWS retrieved by GRACE decreased substantially as a consequence of human activity,while TWS obtained by WBF fluctuated periodically around zero under the impact of three natural drivers;(2) TWS in the NCP fell at a remarkable rate of-12.39 mm/y from 2004 to 2019,and the natural part of TWS experienced two significant declines,during 2004–2010 and 2013–2016;(3) variations in runoff,precipitation,and evapotranspiration from 2004 to 2019 were not significant,but human activities contributed more to the decreasing TWS than natural factors.This study provides a reference for water resource management and groundwater exploitation across the NCP under climate change.

关键词： North China Plain water storage GRACE human activities climatic factor

Drought Change Trend Using MODIS TVDI and Its Relationship with Climate Factors in China from 2001 to 2010

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Journal of Integrative Agriculture 2014年第7期13卷 1501-1508页

作者： LIANG Liang ZHAO Shu-he QIN Zhi-hao HE Ke-xun CHEN Chong LUO Yun-xiao ZHOU Xing-dong School of geographic and Oceanographic sciences Nanjing University School of Geodesy and Geomatics Jiangsu Normal University jiangsu provincial key Laboratory of geographic information science and technology Nanjing University Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences

Changes in drought trends and its relationship with climate change in China were examined in this study. The temperature vegetation drought index （TVDI） datasets recorded during 2001 to 2010 in China were constructed by using the moderate-resolution imaging spectroradiometer （MODIS） data, and the temporal and spatial variations in drought were analyzed. In addition, the mean temperature, mean precipitation, mean relative humidity, and mean sunshine duration data collected from 557 local weather stations in China were analyzed. The relationships between drought and these climate factors were also analyzed by using correlation analysis and partial correlation analysis. Changes in drought tendency were shown to differ among four regions throughout the country. The lfuctuations in climate in the regions of northeastern China, Qinling-Huaihe, and central Qinghai were caused by the increase in soil moisture, and that in southern Tibet was caused by the intensiifcation of drought. Meteorological factors exhibited varied effects on drought among the regions. In southern China, the main inlfuential factor was temperature;other factors only showed minimal effects. That in the northern and northwestern regions was sunshine duration, and those in the Qinghai-Tibet Plateau were relative humidity and temperature.

关键词： drought climate factors TVDI MODIS China

Accelerated glacier mass loss in the southeastern Tibetan Plateau since the 1970s

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Advances in Climate Change Research 2023年第3期14卷 372-386页

作者： Lan-Hua LUO Chang-Qing KE Yu-Bin FAN Zi-Fei WANG jiangsu provincial key Laboratory of geographic information science and technology Key Laboratory for Land Satellite Remote Sensing Applications of Ministry of Natural ResourcesSchool of Geography and Ocean ScienceNanjing UniversityNanjing 210023China Collaborative Innovation Center of Novel Software technology and Industrialization Nanjing 210023China Collaborative Innovation Center of South China Sea Studies Nanjing 210023China

The southeastern Tibetan Plateau(SETP)is a region in High Mountain Asia with the most serious glacier mass loss.However,long-term and large regional-scale studies that estimate glacier mass balance in this area remain limited.In this study,we generated a KH-9 Digital Elevation Model(DEM)(covering 87.6%of the glacier area)for the 1970s from KH-9 Hexagon imagery and quantified geodetic glacier mass over the SETP from the 1970s to 2020 using KH-9 DEM,NASADEM and ICESat-2 ATL06 data.The results show that the SETP was in a state of serious mass loss(at a rate of−0.35±0.03 m w.***.per year)from the 1970s to 2020,and the rate of mass loss accelerated from−0.15±0.05 to−0.56±0.10 m w.***.per year between the 1970s–2000 and 2000–2020.Within the SETP,the glacier mass balance revealed a remarkable spatial heterogeneity.The maximum mean glacier mass loss rate was observed in the Hengduan Shan.Nyainqentanglha exhibited the highest acceleration in the mass loss rate since the 1970s.The warming of air temperature and decreasing snowfall can partly explain the accelerated glacier mass loss in the SETP.The study provides a new long-term glacier mass balance estimation covering almost the entire SETP that suggests the acceleration in glacier mass loss observed in the SETP since the 1970s is a regional tendency,which is crucial for understanding the relationship between glaciers and climate changes.

关键词： Glacier mass balance KH-9 hexagon imagery NASADEM ICESat-2 Southeastern Tibetan Plateau