Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geom...Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geometric characteristics of the ocean eddies in the South China Sea（SCS）. However, very few studies attempt to examine eddies＇ internal evolution processes. In this study, we reported a hybrid method to trace eddies＇ propagation in the SCS based on their internal structures, which are characterized by eddy centers, footprint borders, and composite borders. Eddy identification and tracking results were represented by a GIS-based spatiotemporal model. Information on instant states, dynamic evolution processes, and events of disappearance, reappearance, split, and mergence is stored in a GIS database. Results were validated by comparing against the ten Dongsha Cyclonic Eddies（DCEs） and the three long-lived anticyclonic eddies（ACEs） in the northern SCS, which were reported in previous literature. Our study confirmed the development of these eddies. Furthermore, we found more DCE-like and ACE-like eddies in these areas from 2005 to 2012 in our database. Spatial distribution analysis of disappearing, reappearing, splitting, and merging activities shows that eddies in the SCS tend to cluster to the northwest of Luzon Island, southwest of Luzon Strait, and around the marginal sea of Vietnam. Kuroshio intrusions and the complex sea floor topography in these areas are the possible factors that lead to these spatial clusters.展开更多
The eddy tracking approach is developed using the global nearest neighbor filter（GNNF） to investigate the evolution processes and behaviors of mesoscale eddies in the South China Sea（SCS）. Combining the Kalman fil...The eddy tracking approach is developed using the global nearest neighbor filter（GNNF） to investigate the evolution processes and behaviors of mesoscale eddies in the South China Sea（SCS）. Combining the Kalman filter and optimal data association technologies, the GNNF algorithm is able to reduce pairing errors to 0.2% in tracking synthetic eddy tracks, outperforming other existing methods. A total of 4 913 eddy tracks that last more than a week are obtained by the GNNF during 1993–2012. The analysis of a growth and a decay based on 3 445 simple eddy tracks show that eddy radius, amplitude, and vorticity smoothly increase during the first half of lifetime and decline during the second half following a parabola opening downwards. The genesis of eddies mainly clusters northwest and southwest of Luzon Island whereas the dissipations concentrate the Xisha Islands where the underwater bay traps and terminates eddies. West of the Luzon Strait, northwest of Luzon Island, and southeast of Vietnam are regions where eddy splits and mergers are frequently observed. Short disappearances mainly distribute in the first two regions. Moreover, eddy splits generally result in a decrease of the radius and the amplitude whereas eddy mergers induce growing up. Eddy intensity and vorticity, on the contrary, are strengthened in the eddy splits and diminished in mergers.展开更多
As one of the most ecologically sensitive issues in the world,migration now plays an important role in population growth on the Qinghai-Tibet Plateau.To promote sustainable development in the world’s third pole,it is...As one of the most ecologically sensitive issues in the world,migration now plays an important role in population growth on the Qinghai-Tibet Plateau.To promote sustainable development in the world’s third pole,it is necessary to investigate population migration on the Plateau.Using 2010 census data,a spatial database of county-level migrants on the Plateau was constructed,and migrants were divided into short-distance and long-distance migrants according to the hukou-registered origins.Measuring migration intensity allowed the spatial pattern of population migration on the Plateau to be ascertained.The driving factors were identified using spatial regression models,and the main conclusions are as follows:(1)In 2010,there were 1.23 million inter-county migrants on the Qinghai-Tibet Plateau,and the overall migration intensity reached 10.50%.There existed significant spatial differences in population migration intensity on the Plateau at that time,and the provincial or prefectural capitals were attractive destinations for migrants.Northwestern Qinghai,which boasted mining industries,constituted a significant spatial cluster with a relatively high migration intensity.However,most areas on the Plateau attracted relatively few migrants,especially in western and northern parts of Tibet,which were sparsely populated and uninhabitable.(2)There were 0.95 million short-distance migrants and 0.28 million long-distance migrants.The short-distance migration intensity was 8.14%,while the long-distance migration intensity was only 2.36%.Short-distance migration was the main form of population migration,with a pattern similar to the layout of overall population migration intensity.Only a few county-level units strongly attracted long-distance migrants,which were mostly distributed in northwestern Qinghai.(3)Economic factors were considered fundamental drivers for migrants to live on the Plateau.Destinations with high levels of economic development and more opportunities in non-agricultural jobs proved more attractive for migrants.For short-distance migrants,urbanization level also proved a considerable driving factor for in-migration.However,long-distance migrants were mainly affected by the job chances of the secondary industry on the Qinghai-Tibet Plateau.展开更多
Developing a comprehensive understanding of inter-city interactions is crucial for regional planning.We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau(QTP)using mig...Developing a comprehensive understanding of inter-city interactions is crucial for regional planning.We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau(QTP)using migration big data from Tencent for the period between 2015 and 2019.We initially used decomposition and breakpoint detection methods to examine time-series migration data and to identify the two seasons with the strongest and weakest population migration levels,between June 18th and August 18th and between October 8th and February 15th,respectively.Population migration within the former period was 2.03 times that seen in the latter.We then used a variety of network analysis methods to examine population flow directions as well as the importance of each individual city in migration.The two capital cities on the QTP,Lhasa and Xining,form centers for population migration and are also transfer hubs through which migrants from other cities off the plateau enter and leave this region.Data show that these two cities contribute more than 35%of total population migration.The majority of migrants tend to move within the province,particularly during the weakest migration season.We also utilized interactive relationship force and radiation models to examine the interaction strength and the radiating energy of each individual city.Results show that Lhasa and Xining exhibit the strongest interactions with other cities and have the largest radiating energies.Indeed,the radiating energy of the QTP cities correlates with their gross domestic product(GDP)(Pearson correlation coefficient:0.754 in the weakest migration season,WMS versus 0.737 in the strongest migration season,SMS),while changes in radiating energy correlate with the tourism-related revenue(Pearson correlation coefficient:0.685).These outcomes suggest that level of economic development and level of tourism are the two most important factors driving the QTP population migration.The results of this analysis provide critical clarification guidance regarding huge QTP development differences.展开更多
Mobile internet and wireless communication technologies have produced unprecedented location-aware data.Such big geospatial data can be used as a proxy measure of the‘digital footprints’left by us on the planet and ...Mobile internet and wireless communication technologies have produced unprecedented location-aware data.Such big geospatial data can be used as a proxy measure of the‘digital footprints’left by us on the planet and provide a valuable opportunity to understand the dynamic and short-term human disturbance on the nature at fine scales.This study investigated the spatiotemporal variations of human’s digital footprints on the Qinghai-Tibet Plateau using smartphone-users-generated Tencent’s location request data.The results showed that human’s digital footprints cover less than 5%of Qinghai and Tibet,exhibiting either a U-shaped or an N-shaped temporal change pattern during the major festivals.Spatial changes of the digital footprints manifested a transition process from dispersion to concentration in Xining and Lhasa.Human disturbance assessment of seven large nature reserves on the plateau showed that the Qinghai Lake is the most disturbed one as shown by 14.6%of its area is stained with human digital footprints and the areal average of footprint intensity is 1.59,and the disturbance was significantly escalated during the National Day holiday.By contrast,the Qangtang and Hoh Xil are the least affected nature reserves with the two indices less than 1%and 0.1,respectively.展开更多
基金The National Science Foundation of China under contract Nos 41071250 and 41371378the Innovation Projects of the State Key Laboratory of Resource and Environment Information System,Chinese Academy of Sciences,under contract No.088RA500TA
文摘Automated identification and tracking of mesoscale ocean eddies has recently become one research hotspot in physical oceanography. Several methods have been developed and applied to survey the general kinetic and geometric characteristics of the ocean eddies in the South China Sea（SCS）. However, very few studies attempt to examine eddies＇ internal evolution processes. In this study, we reported a hybrid method to trace eddies＇ propagation in the SCS based on their internal structures, which are characterized by eddy centers, footprint borders, and composite borders. Eddy identification and tracking results were represented by a GIS-based spatiotemporal model. Information on instant states, dynamic evolution processes, and events of disappearance, reappearance, split, and mergence is stored in a GIS database. Results were validated by comparing against the ten Dongsha Cyclonic Eddies（DCEs） and the three long-lived anticyclonic eddies（ACEs） in the northern SCS, which were reported in previous literature. Our study confirmed the development of these eddies. Furthermore, we found more DCE-like and ACE-like eddies in these areas from 2005 to 2012 in our database. Spatial distribution analysis of disappearing, reappearing, splitting, and merging activities shows that eddies in the SCS tend to cluster to the northwest of Luzon Island, southwest of Luzon Strait, and around the marginal sea of Vietnam. Kuroshio intrusions and the complex sea floor topography in these areas are the possible factors that lead to these spatial clusters.
基金The National Natural Science Foundation of China under contract Nos 41421001 and 41371378
文摘The eddy tracking approach is developed using the global nearest neighbor filter（GNNF） to investigate the evolution processes and behaviors of mesoscale eddies in the South China Sea（SCS）. Combining the Kalman filter and optimal data association technologies, the GNNF algorithm is able to reduce pairing errors to 0.2% in tracking synthetic eddy tracks, outperforming other existing methods. A total of 4 913 eddy tracks that last more than a week are obtained by the GNNF during 1993–2012. The analysis of a growth and a decay based on 3 445 simple eddy tracks show that eddy radius, amplitude, and vorticity smoothly increase during the first half of lifetime and decline during the second half following a parabola opening downwards. The genesis of eddies mainly clusters northwest and southwest of Luzon Island whereas the dissipations concentrate the Xisha Islands where the underwater bay traps and terminates eddies. West of the Luzon Strait, northwest of Luzon Island, and southeast of Vietnam are regions where eddy splits and mergers are frequently observed. Short disappearances mainly distribute in the first two regions. Moreover, eddy splits generally result in a decrease of the radius and the amplitude whereas eddy mergers induce growing up. Eddy intensity and vorticity, on the contrary, are strengthened in the eddy splits and diminished in mergers.
基金The Strategic Priority Research Program of Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road(Pan-TPE)(XDA20040401)The Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK1005)National Natural Sciences Foundation of China(41701165)。
文摘As one of the most ecologically sensitive issues in the world,migration now plays an important role in population growth on the Qinghai-Tibet Plateau.To promote sustainable development in the world’s third pole,it is necessary to investigate population migration on the Plateau.Using 2010 census data,a spatial database of county-level migrants on the Plateau was constructed,and migrants were divided into short-distance and long-distance migrants according to the hukou-registered origins.Measuring migration intensity allowed the spatial pattern of population migration on the Plateau to be ascertained.The driving factors were identified using spatial regression models,and the main conclusions are as follows:(1)In 2010,there were 1.23 million inter-county migrants on the Qinghai-Tibet Plateau,and the overall migration intensity reached 10.50%.There existed significant spatial differences in population migration intensity on the Plateau at that time,and the provincial or prefectural capitals were attractive destinations for migrants.Northwestern Qinghai,which boasted mining industries,constituted a significant spatial cluster with a relatively high migration intensity.However,most areas on the Plateau attracted relatively few migrants,especially in western and northern parts of Tibet,which were sparsely populated and uninhabitable.(2)There were 0.95 million short-distance migrants and 0.28 million long-distance migrants.The short-distance migration intensity was 8.14%,while the long-distance migration intensity was only 2.36%.Short-distance migration was the main form of population migration,with a pattern similar to the layout of overall population migration intensity.Only a few county-level units strongly attracted long-distance migrants,which were mostly distributed in northwestern Qinghai.(3)Economic factors were considered fundamental drivers for migrants to live on the Plateau.Destinations with high levels of economic development and more opportunities in non-agricultural jobs proved more attractive for migrants.For short-distance migrants,urbanization level also proved a considerable driving factor for in-migration.However,long-distance migrants were mainly affected by the job chances of the secondary industry on the Qinghai-Tibet Plateau.
基金National Natural Science Foundation of China(41590845)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19040501)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20040401)National Key Research and Development Program of China(2017YFB0503605)National Key Research and Development Program of China(2017YFC1503003)。
文摘Developing a comprehensive understanding of inter-city interactions is crucial for regional planning.We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau(QTP)using migration big data from Tencent for the period between 2015 and 2019.We initially used decomposition and breakpoint detection methods to examine time-series migration data and to identify the two seasons with the strongest and weakest population migration levels,between June 18th and August 18th and between October 8th and February 15th,respectively.Population migration within the former period was 2.03 times that seen in the latter.We then used a variety of network analysis methods to examine population flow directions as well as the importance of each individual city in migration.The two capital cities on the QTP,Lhasa and Xining,form centers for population migration and are also transfer hubs through which migrants from other cities off the plateau enter and leave this region.Data show that these two cities contribute more than 35%of total population migration.The majority of migrants tend to move within the province,particularly during the weakest migration season.We also utilized interactive relationship force and radiation models to examine the interaction strength and the radiating energy of each individual city.Results show that Lhasa and Xining exhibit the strongest interactions with other cities and have the largest radiating energies.Indeed,the radiating energy of the QTP cities correlates with their gross domestic product(GDP)(Pearson correlation coefficient:0.754 in the weakest migration season,WMS versus 0.737 in the strongest migration season,SMS),while changes in radiating energy correlate with the tourism-related revenue(Pearson correlation coefficient:0.685).These outcomes suggest that level of economic development and level of tourism are the two most important factors driving the QTP population migration.The results of this analysis provide critical clarification guidance regarding huge QTP development differences.
基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20040401)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19040501)+2 种基金National Key Research and Development Program of China(2017YFB0503605)National Key Research and Development Program of China(2017YFC1503003)National Natural Science Foundation of China(41901395)。
文摘Mobile internet and wireless communication technologies have produced unprecedented location-aware data.Such big geospatial data can be used as a proxy measure of the‘digital footprints’left by us on the planet and provide a valuable opportunity to understand the dynamic and short-term human disturbance on the nature at fine scales.This study investigated the spatiotemporal variations of human’s digital footprints on the Qinghai-Tibet Plateau using smartphone-users-generated Tencent’s location request data.The results showed that human’s digital footprints cover less than 5%of Qinghai and Tibet,exhibiting either a U-shaped or an N-shaped temporal change pattern during the major festivals.Spatial changes of the digital footprints manifested a transition process from dispersion to concentration in Xining and Lhasa.Human disturbance assessment of seven large nature reserves on the plateau showed that the Qinghai Lake is the most disturbed one as shown by 14.6%of its area is stained with human digital footprints and the areal average of footprint intensity is 1.59,and the disturbance was significantly escalated during the National Day holiday.By contrast,the Qangtang and Hoh Xil are the least affected nature reserves with the two indices less than 1%and 0.1,respectively.
