Here,we analyze the characteristics and the formation mechanisms of low-level jets(LLJs)in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth genera...Here,we analyze the characteristics and the formation mechanisms of low-level jets(LLJs)in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5)reanalysis dataset.Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs)concentrated at heights of 900-1200 m.The BLJs occur most frequently at 2300 LST(LST=UTC+8 hours)but are strongest at 0200 LST,with composite wind velocities>14 m s^(-1).Synoptic-system-related LLJs(SLLJs)occur most frequently at 0800 LST but are strongest at 1100LST,with composite wind velocities>12 m s^(-1).Both BLJs and SLLJs are characterized by a southwesterly wind direction,although the wind direction of SLLJs is more westerly,and northeasterly SLLJs occur more frequently than northeasterly BLJs.When Wuhan is south of the mei-yu front,the westward extension of the northwest Pacific subtropical high intensifies,and the low-pressure system in the eastern Tibetan Plateau strengthens,favoring the formation of LLJs,which are closely related to precipitation.The wind speeds on rainstorm days are greater than those on LLJ days.Our analysis of four typical heavy precipitation events shows the presence of LLJs at the center of the precipitation and on its southern side before the onset of heavy precipitation.BLJs were shown to develop earlier than SLLJs.展开更多
Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has 'two-layer str...Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has 'two-layer structure' and partly has 'multi-layered structure', and is inhomogeneous and shows the distinct feature of E-W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800-2000 Ma and 1200-1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low.展开更多
In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Netwo...In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Networks Center)in the study area.We adopted the double-difference seismic tomographic method(tomo DD)to invert the 3-D P-wave velocity structure and constrain the crust-upper mantle architecture of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt(MLYB).A 1-D initial model extracted from wide-angle seismic profiles was used in the seismic tomography,which greatly reduced the inversion residual.Our results indicate that reliable velocity structure of th e uppermost mantle can be obtained when Pn is involved in the tomography.Our results show that:(1)the pattern of the uppermost mantle velocity structure corresponds well with the geological partitioning:a nearly E-W-trending low-velocity zone is present beneath the Dabie Orogen,in contrast to the mainly NE-trending low-velocity anomalies beneath the Jiangnan Orogen.They suggest the presence of thickened lower crust beneath the orogens in the study area.In contrast,the Yangtze and Cathaysia blocks are characterized by relatively high-velocity anomalies;(2)both the ultra-high-pressure(UHP)metamorphic rocks in the Dabie Orogen and the low-pressure metamorphic rocks in the Zhangbaling dome are characterized by high-velocity anomalies.The upper crust in the Dabie Orogen is characterized by a low-velocity belt,sandwiched between two high velocity zones in a horizontal direction,with discontinuous low-velocity layers in the middle crust.The keel of the Dabie Orogen is mainly preserved beneath its northern section.We infer that the lower crustal delamination may have mainly occurred in the southern Dabie Orogen,which caused the mantle upwelling responsible for the formation of the granitic magmas emplaced in the middle crust as the low-velocity layers observed there.Continuous deep-level compression likely squeezed the granitic magma upward to intrude the upper crustal UHP metamorphic rocks,forming the'sandwich'velocity structure there;(3)high-velocity updoming is widespread in the crust-mantle transition zone beneath the MLYB.From the Anqing-Guichi ore field northeastward to the Luzong,Tongling,Ningwu and Ningzhen orefields,high-velocity anomalies in the crust-mantle transition zone increase rapidly in size and are widely distributed.The updoming also exists in the crust-mantle transition zone beneath the Jiurui and Edongnan orefields,but the high-velocity anomalies are mainly stellate distributed.The updoming high-velocity zone beneath the MLYB generally extends from the crust-mantle transition zone to the middle crust,different from the velocity structure in the upper crust.The upper crust beneath the Early Cretaceous extension-related Luzong and Ningwu volcanic basins is characterized by high velocity zones,in contrast to the low velocity anomalies beneath the Late Jurassic to Early Cretaceous compression-related Tongling ore field.The MLYB may have undergone a compressive-to-extensional transition during the Yanshanian(Jurassic-Cretaceous)period,during which extensive magmatism occurred.The near mantle-crustal boundary updoming was likely caused by asthenospheric underplating at the base of the lower crust.The magmas may have ascended through major crustal faults,undergoing AFC(assimilation and fractional crystallization)processes,became emplaced in the fault-bounded basins or Paleozoic sequences,eventually forming the many Cu-Fe polymetallic deposits there.展开更多
Identification of the spatial mismatch between land use functions(LUFs)and land use efficiencies(LUEs)is essential to regional land use policies.However,previous studies about LUF-LUE mismatch and its driving factors ...Identification of the spatial mismatch between land use functions(LUFs)and land use efficiencies(LUEs)is essential to regional land use policies.However,previous studies about LUF-LUE mismatch and its driving factors have been insufficient.In this study,we explored the spatiotemporal mismatch of LUFs and LUEs and their influencing factors from 2000 to 2018 in the Middle Reaches of the Yangtze River(MRYR).Specifically,we used Spearman correlation analysis to reveal the trade-off relationship between LUFs and LUEs and determine the direction of the influencing factors on the LUF-LUE mismatch,adopted spatial mismatch analysis to measure the imbalance between LUFs and LUEs,and used the geographical detector model to analyze the factors influencing this spatial mismatch.The results showed that production function(PDF),living function(LVF),ecological function(ELF),agricultural production efficiency(APE),urban construction efficiency(UCE),and ecological services efficiency(ESE)all displayed significant spatial heterogeneity.The high trade-off areas were widely distributed and long-lasting in agricultural space and urban space,while gradually decreasing in ecological space.Wuhan and Changsha showed high spatial mismatch coefficients in urban space,but low spatial mismatch coefficients in agricultural space.Hunan generally presented high spatial mismatch coefficients in ecological space.Furthermore,the interaction of the proportion of cultivated area and transportation accessibility exacerbated the mismatch in agricultural space.The interaction effects of capital investment and technology innovation with other factors have the most intense impact on the mismatch in urban space.The internal factor for cultivated area interacts with other external factors to drastically affect ecological spatial mismatch.展开更多
Land spaces function in capacities of urban development,agricultural production,and ecological conservation,among many others.Research of land space utilization efficiency(LSUE)and coupling coordination relationships ...Land spaces function in capacities of urban development,agricultural production,and ecological conservation,among many others.Research of land space utilization efficiency(LSUE)and coupling coordination relationships among its subsystems are significant for sustainable land space development.In this study,taking the Urban Agglomeration in the Middle Reaches of the Yangtze River(UAMRYR)as the study area,we establish a measurement index system to evaluate the LSUE(2000–2018)and analyze its coupling coordination degree by utilizing an improved coupling coordination model.The main results include the following.(1)The average efficiency levels of urban space and agricultural space in the UAMRYR increased 2000–2018,while the average efficiency of ecological space declined.(2)The spatial pattern of the LSUE values varied greatly,with the distributions of high-efficiency and low-efficiency levels significantly different.(3)The coupling degree of LSUE includes three types,i.e.,high-level coupling,break-in,and antagonism.Each coupling degree type was characterized by change over time.(4)The proportion of areas with high coupling coordination and moderate coupling coordination increased from 2000 to 2018,while the proportion of areas with basic coupling coordination,moderate imbalance,and serious imbalance declined during this period.Given that the spatial differentiation of the LSUE and its coupling coordination,it is necessary to implement a differential land space development strategy in the UAMRYR.This study is helpful to promote the efficient utilization and coordinated development of land space utilization systems.展开更多
Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body te...Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body temperature(TBB) dataset during May to August 2000–2016(except 2005). The MCSs were divided into eastward-propagating(EP) and quasi-stationary(QS) types, to compare their spatial and temporal distributions and convective intensities, and to identify the favorable synoptic conditions for the formation and evolution of EP MCSs. The results showed that both MCS types occurred most often in July. The EP MCSs were mainly initiated over the eastern regions of the study area, while the QS type mainly originated in the western regions of the study area. Both MCS types mainly formed in the afternoon, but a second peak occurred in the early morning for QS MCSs. The EP MCSs had a larger cloud area at their mature stage and a lower cloud brightness temperature, indicating more intense convection. Additionally, the longer lifetime and further eastward propagation of the EP MCSs meant that they had a great influence on the precipitation over the middle and lower reaches of the Yangtze River. Synoptic circulation analysis demonstrated that the combination of the mid-level low trough east of the Tibetan Plateau(TP), and the western pacific subtropical high(WPSH), favored the formation and eastward propagation of EP MCSs. The positive vertical relative vorticity and stronger vertical wind shear provided dynamic conditions favorable for convective organization and development. Furthermore, a stronger low level jet imported warm and moist air to the eastern edge of, and the regions east of, the second-step terrain. The substantial convergence of water vapor promoted the development and long-lived maintenance of the EP MCSs.展开更多
To investigate the multi-scale features in two persistent heavy rainfall(PHR) events in the middle and lower reaches of the Yangtze River(MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale ...To investigate the multi-scale features in two persistent heavy rainfall(PHR) events in the middle and lower reaches of the Yangtze River(MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale oscillations in the north and south of 30?N on the PHR events by performing sensitivity experiments with the Weather Research and Forecast(WRF) model. It is found that the 60-day lowpass perturbation made a trivial contribution to the MLRYR precipitation during the PHR event in 1982.This PHR event resulted mainly from the combined effects of 30–60-day oscillation at low latitudes and10–30-day oscillation at both high and low latitudes. The southwesterly anomalies associated with the 30–60-day anticyclonic anomaly over the northwestern Pacific facilitated moisture transport from the ocean to the MLRYR and enhanced the low-level convergence and ascending motion in the MLRYR. This similarly occurred in the 10–30-day oscillation as well. Moreover, the 10–30-day anomalies at high latitudes played a role in strengthening the large-scale low-level convergence over the MLRYR. The PHR event in 1998 was mainly related to the 60-day oscillation at both high and low latitudes and 30–60-day oscillation at low latitudes. The 60-day low-pass filtered anomalous cyclone at high latitudes in the north of 30?N contributed to the development of low-level convergence and ascending motion in northern MLRYR while the anomalous anticyclone at low latitudes in the south of 30?N not only increased the moisture in the MLRYR but also preconditioned the dynamical factors favorable for PHR over the whole area. The 30–60-day perturbations located north and south of 30?N worked together producing positive moisture anomaly in the MLRYR.In addition, the anomalous circulation in the south of 30?N tended to favor the development of ascending motion and low-level convergence in the MLRYR.展开更多
Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle r...Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle reaches of the Yangtze River, and compares them with findings in other areas. Results are as follows: radiation fog in Xuanen is evidently weaker in droplet number concentration and liquid water content than land fogs in other areas. Its liquid water content fluctuates obviously, 0.01g/m3 with visibility of 1,000 meters, which is quite different from that in urban areas, but similar to the Nanling Mountains. Bi-modal droplet distribution is likely to occur in Xuanen mountain radiation fog(MRF) events. Statistical analysis shows that the observed droplet size distribution can be piecewise described well by the Gamma distribution. There is a positive correlation between liquid water content, fog droplet concentration and mean radius, especially in the development and dissipation stage. Condensation growth and droplet evaporation are major processes of Xuanen MRF. The dissipation time coincided with the time when the grass temperature reached the peak value, which indicated that dew evaporation is a key role in maintaining Xuanen MRF. In the early stage of dense fog's growth, droplets with diameter of over 20 micrometers can be observed with visibility of800-1,000 m, which might be caused by the transportation of low cloud droplets to earth's surface by turbulence. Big droplets in the initial stage correspond to higher water content, leading to the higher observed value of water content of Xuanen MRF.展开更多
To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan...To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan in Zhejiang.This profile traverses the Cu-Au metallogenic belt in the middle and lower reaches of the Yangtze River(YMB),the Jiangnan W-polymetal metallogenic belt(JNMB),and the Qinhang Cu-polymetal metallogenic belt(QHMB).Our imaging results reveal various interesting velocity features along the profile.(1)The velocity structure is characterized by vertical layering and horizontal blocking;(2)the YMB is marked by high velocity and high V_(p)/V_(s) ratios in general with a significantly uplifted Moho interface and a thin crust of~31 km,and the lower crust contains high-velocity anomalies and has the characteristics of a crustmantle transition zone;(3)the JNMB is bounded by the Jiangnan fault and Jingdezhen-Huangshan fault and has low-velocity anomalies and low V_(p)/V_(s) ratios;and(4)the QHMB is characterized by high-velocity anomalies and high V_(p)/V_(s) ratios.The highvelocity anomalies in the YMB and QHMB represent relatively Cu-Au-rich mafic juvenile lower crust.The formation of this kind of crust is considered to be related to mantle-derived magma underplating or residues of Neoproterozoic oceanic crustal materials,and it also provided sources for large-scale Cu-Au mineralization in the Mesozoic.The JNMB has features similar to those of ancient crusts enriched in W-Sn,the partial melting of which played a leading role in the formation of the superlarge W deposits in this belt.Considering these results and other regional geological data,we propose that a large-scale oblique upwelling of the asthenosphere along the collisional belt of the Yangtze and Cathaysia blocks during the Mesozoic was the deep driving mechanism for the explosive mineralization of Cu,Au,and W in northeastern South China.The boundaries of the blocks or terrains and discontinuities of the lithosphere were the main channels for deep heat and magmas and therefore controlled the spatial distribution of the metallogenic belt.展开更多
Given the importance of waterway depths in river development,the effects of the evolution of bars and troughs on waterway expansion play an important role in river management and water depth conservation.This study ai...Given the importance of waterway depths in river development,the effects of the evolution of bars and troughs on waterway expansion play an important role in river management and water depth conservation.This study aims to expand the waterway dimensions of the Jingjiang Reach of the Yangtze River.To achieve this objective,determining the relationship between river evolution processes and the potential for waterway depth improvement and navigation hindrances is vital.Therefore,the sedimentation,hydrological,and terrain data of the Jingjiang Reach from 1955 to 2020 are analysed to elucidate the above-mentioned relationship.Since the commissioning of the Three Gorges Dam,the scouring of the low-flow channel has accounted for 90%-95%of all scouring in the Jingjiang Reach.Furthermore,the central bars and beaches have shrunk by 9.4%and 24.9%,respectively,and 18.3%overall.Considering the bed scouring and waterway regulation projects in the Jingjiang Reach,we investigated the continuity of a 4.5 m×200 m×1050 m(depth×width×bend radius)waterway along the Jingjiang Reach,and find that navigation-hindering channels account for over 5.3%of the waterway length.Furthermore,part of the Jingjiang Reach is an important nature reserve and shelters numerous water-related facilities,which inhibits the implementation of waterway deepening projects.The findings of this study demonstrate that numerous challenges are associated with increasing the waterway depths of the Jingjiang Reach.展开更多
The operation of large-scale reservoirs have modified water and sediment transport processes,resulting in adjustments to the river topography and water levels.The polynomial fitting method was applied to analyze the v...The operation of large-scale reservoirs have modified water and sediment transport processes,resulting in adjustments to the river topography and water levels.The polynomial fitting method was applied to analyze the variation characteristics of water levels under different water discharge values in the Jingjiang reach of the Yangtze River from 1991–2016.The segregation variable method was used to estimate the contributions of the varied riverbed evaluation,the downstream-controlled water level,and the comprehensive roughness on the altered water level at an identical flow.We find that low water levels in the Jingjiang reach of the Yangtze River from 1991–2016 are characterized by a significant downward trend,which has intensified since 2009.Riverbed scouring has been the dominate factor causing the reduced low water level while increased roughness alleviated this reduction.From 1991–2016,there was first a decrease followed by an increase in the high water level.The variation characteristic in terms of the'high flood discharge at a high water level'before 2003 transformed into a'middle flood discharge at a high water level'since 2009.The increased comprehensive roughness was the main reason for the increased high water level,where river scouring alleviated this rise.For navigation conditions and flood control,intensified riverbed scouring of the sandy reaches downstream from dams enhanced the effects that the downstream water level has on the upstream water level.This has led to an insufficient water depth in the reaches below the dams,which should receive immediate attention.The alteredvariation characteristics of the high water level have also increased the flood pressure in the middle reaches of the Yangtze River.展开更多
The spatial relationships between traffic accessibility and supply and demand(S&D)of ecosystem services(ESs)are essential for the formulation of ecological compensation policies and ESs regulation.In this study,an...The spatial relationships between traffic accessibility and supply and demand(S&D)of ecosystem services(ESs)are essential for the formulation of ecological compensation policies and ESs regulation.In this study,an ESs matrix and coupling analysis method were used to assess ESs S&D based on land-use data for 2000,2010,and 2020,and spatial regression models were used to analyze the correlated impacts of traffic accessibility.The results showed that the ESs supply and balance index in the middle reaches of the Yangtze River urban agglomeration(MRYRUA)continuously decreased,while the demand index increased from 2000 to 2020.The Gini coefficients of these indices continued to increase but did not exceed the warning value(0.4).The coupling degree of ESs S&D continued to increase,and its spatial distribution patterns were similar to that of the ESs demand index,with significantly higher values in the plains than in the montane areas,contrasting with those of the ESs supply index.The results of global bivariate Moran’s I analysis showed a significant spatial dependence between traffic accessibility and the degree of coupling between ESs S&D;the spatial regression results showed that an increase in traffic accessibility promoted the coupling degree.The present results provide a new perspective on the relationship between traffic accessibility and the coupling degree of ESs S&D,representing a case study for similar future research in other regions,and a reference for policy creation based on the matching between ESs S&D in the MRYRUA.展开更多
Since the launch of China’s reform and opening up policy,the process of urbanization in China has accelerated significantly.With the development of cities,inter-city interactions have become increasingly close,formin...Since the launch of China’s reform and opening up policy,the process of urbanization in China has accelerated significantly.With the development of cities,inter-city interactions have become increasingly close,forming urban agglomerations that tend to be integrated.Urban agglomerations are regional spaces with network relationships and hierarchies,and have always been the main units for China to promote urbanization and regional coordinated development.In this paper,we comprehensively consider the network and hierarchical characteristics of an urban agglomeration,while using urban flow to describe the interactions of the inter-city networks and the hierarchical generalized linear model(HGLM)to reveal the hierarchical driving mechanism of the urban agglomeration.By coupling the HGLM with a cellular automata(CA)model,we introduced the HGLM-CA model for the simulation of the spatial expansion of an urban agglomeration,and compared the simulation results with those of the logistic-CA model and the biogeography-based optimization CA(BBO-CA)model.According to the results,we further analyzed the advantages and disadvantages of the proposed HGLM-CA model.We selected the middle reaches of the Yangtze River in China as the research area to conduct this empirical research,and simulated the spatial expansion of the urban agglomeration in 2017 on the basis of urban land-use data from 2007 and 2012.The results indicate that the spatial expansion of the urban agglomeration can be attributed to various driving factors.As a driving factor at the urban level,urban flow promotes the evolution of land use in the urban agglomeration,and also plays an important role in regulating cell-level factors,making the cell-level factors of different cities show different driving effects.The HGLM-CA model is able to obtain a higher simulation accuracy than the logistic-CA model,which indicates that the simulation results for urban agglomeration expansion considering urban flow and hierarchical characteristics are more accurate.When compared with the intelligent algorithm model,i.e.,BBO-CA,the HGLM-CA model obtains a lower simulation accuracy,but it can analyze the interaction of the various driving factors from a hierarchical perspective.It also has a strong explanatory effect for the spatial expansion mechanism of urban agglomerations.展开更多
The continuous degradation of ecosystem services is an important challenge faced by the world.Improvements in transportation infrastructure have had substantial impacts on economic development and ecosystem services.E...The continuous degradation of ecosystem services is an important challenge faced by the world.Improvements in transportation infrastructure have had substantial impacts on economic development and ecosystem services.Exploring the influence of traffic accessibility on ecosystem services can delay or stop their deterioration;however,studies on its impact are lacking.This study addresses this gap by analysing the impact of traffic accessibility on ecosystem services using an integrated spatial regression approach based on an evaluation of the ecosystem services value(ESV)and traffic accessibility in the Middle Reaches of the Yangtze River Urban Agglomeration(MRYRUA)in China.The results indicated that the ESV in the MRYRUA continuously decreased during the study period,and the average ESV in plain areas,areas surrounding the core cities,and areas along the main traffic routes was significantly lower than that in areas along the Yangtze River and the surrounding mountainous areas.Traffic accessibility continued to increase during the study period,and the high-value areas centred on Wuhan,Changsha,Nanchang,and Yichang were radially distributed.The global bivariate spatial autocorrelation coefficient between the average ESV and traffic accessibility was negative.The average ESV and traffic accessibility exhibited significant spatial dependence and spatial heterogeneity.Spatial regression also proved that there was a negative association between the average ESV and traffic accessibility,and scale effects were evident.The findings of this study have important policy implications for future ecological protection and transportation planning.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42230612,41620104009,41705019,42075186,and 41975058)the Projects of the S&T Development Foundation of the Hubei Meteorological Bureau(Grants No.2021Q04 and 2020Y04)。
文摘Here,we analyze the characteristics and the formation mechanisms of low-level jets(LLJs)in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5)reanalysis dataset.Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs)concentrated at heights of 900-1200 m.The BLJs occur most frequently at 2300 LST(LST=UTC+8 hours)but are strongest at 0200 LST,with composite wind velocities>14 m s^(-1).Synoptic-system-related LLJs(SLLJs)occur most frequently at 0800 LST but are strongest at 1100LST,with composite wind velocities>12 m s^(-1).Both BLJs and SLLJs are characterized by a southwesterly wind direction,although the wind direction of SLLJs is more westerly,and northeasterly SLLJs occur more frequently than northeasterly BLJs.When Wuhan is south of the mei-yu front,the westward extension of the northwest Pacific subtropical high intensifies,and the low-pressure system in the eastern Tibetan Plateau strengthens,favoring the formation of LLJs,which are closely related to precipitation.The wind speeds on rainstorm days are greater than those on LLJ days.Our analysis of four typical heavy precipitation events shows the presence of LLJs at the center of the precipitation and on its southern side before the onset of heavy precipitation.BLJs were shown to develop earlier than SLLJs.
基金This study was supported by the National Natural Science Foundation of China grant 49802007.
文摘Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has 'two-layer structure' and partly has 'multi-layered structure', and is inhomogeneous and shows the distinct feature of E-W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800-2000 Ma and 1200-1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low.
基金funded by grants from the Key Project of the National Natural Science Foundation of China(No.41630320)the National Key Research and Development Program of China(No.2016YFC0600200)the Hefei Postdoctoral Science Foundation。
文摘In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Networks Center)in the study area.We adopted the double-difference seismic tomographic method(tomo DD)to invert the 3-D P-wave velocity structure and constrain the crust-upper mantle architecture of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt(MLYB).A 1-D initial model extracted from wide-angle seismic profiles was used in the seismic tomography,which greatly reduced the inversion residual.Our results indicate that reliable velocity structure of th e uppermost mantle can be obtained when Pn is involved in the tomography.Our results show that:(1)the pattern of the uppermost mantle velocity structure corresponds well with the geological partitioning:a nearly E-W-trending low-velocity zone is present beneath the Dabie Orogen,in contrast to the mainly NE-trending low-velocity anomalies beneath the Jiangnan Orogen.They suggest the presence of thickened lower crust beneath the orogens in the study area.In contrast,the Yangtze and Cathaysia blocks are characterized by relatively high-velocity anomalies;(2)both the ultra-high-pressure(UHP)metamorphic rocks in the Dabie Orogen and the low-pressure metamorphic rocks in the Zhangbaling dome are characterized by high-velocity anomalies.The upper crust in the Dabie Orogen is characterized by a low-velocity belt,sandwiched between two high velocity zones in a horizontal direction,with discontinuous low-velocity layers in the middle crust.The keel of the Dabie Orogen is mainly preserved beneath its northern section.We infer that the lower crustal delamination may have mainly occurred in the southern Dabie Orogen,which caused the mantle upwelling responsible for the formation of the granitic magmas emplaced in the middle crust as the low-velocity layers observed there.Continuous deep-level compression likely squeezed the granitic magma upward to intrude the upper crustal UHP metamorphic rocks,forming the'sandwich'velocity structure there;(3)high-velocity updoming is widespread in the crust-mantle transition zone beneath the MLYB.From the Anqing-Guichi ore field northeastward to the Luzong,Tongling,Ningwu and Ningzhen orefields,high-velocity anomalies in the crust-mantle transition zone increase rapidly in size and are widely distributed.The updoming also exists in the crust-mantle transition zone beneath the Jiurui and Edongnan orefields,but the high-velocity anomalies are mainly stellate distributed.The updoming high-velocity zone beneath the MLYB generally extends from the crust-mantle transition zone to the middle crust,different from the velocity structure in the upper crust.The upper crust beneath the Early Cretaceous extension-related Luzong and Ningwu volcanic basins is characterized by high velocity zones,in contrast to the low velocity anomalies beneath the Late Jurassic to Early Cretaceous compression-related Tongling ore field.The MLYB may have undergone a compressive-to-extensional transition during the Yanshanian(Jurassic-Cretaceous)period,during which extensive magmatism occurred.The near mantle-crustal boundary updoming was likely caused by asthenospheric underplating at the base of the lower crust.The magmas may have ascended through major crustal faults,undergoing AFC(assimilation and fractional crystallization)processes,became emplaced in the fault-bounded basins or Paleozoic sequences,eventually forming the many Cu-Fe polymetallic deposits there.
基金Key Project of the National Social Science Foundation of China,No.23AZD058National Natural Science Foundation of China,No.72004209。
文摘Identification of the spatial mismatch between land use functions(LUFs)and land use efficiencies(LUEs)is essential to regional land use policies.However,previous studies about LUF-LUE mismatch and its driving factors have been insufficient.In this study,we explored the spatiotemporal mismatch of LUFs and LUEs and their influencing factors from 2000 to 2018 in the Middle Reaches of the Yangtze River(MRYR).Specifically,we used Spearman correlation analysis to reveal the trade-off relationship between LUFs and LUEs and determine the direction of the influencing factors on the LUF-LUE mismatch,adopted spatial mismatch analysis to measure the imbalance between LUFs and LUEs,and used the geographical detector model to analyze the factors influencing this spatial mismatch.The results showed that production function(PDF),living function(LVF),ecological function(ELF),agricultural production efficiency(APE),urban construction efficiency(UCE),and ecological services efficiency(ESE)all displayed significant spatial heterogeneity.The high trade-off areas were widely distributed and long-lasting in agricultural space and urban space,while gradually decreasing in ecological space.Wuhan and Changsha showed high spatial mismatch coefficients in urban space,but low spatial mismatch coefficients in agricultural space.Hunan generally presented high spatial mismatch coefficients in ecological space.Furthermore,the interaction of the proportion of cultivated area and transportation accessibility exacerbated the mismatch in agricultural space.The interaction effects of capital investment and technology innovation with other factors have the most intense impact on the mismatch in urban space.The internal factor for cultivated area interacts with other external factors to drastically affect ecological spatial mismatch.
基金National Natural Science Foundation of China,No.42171249,No.42201270National Social Science Foundation of China,No.20BJY119Jiangsu Social Science Foundation,No.18GLC016。
文摘Land spaces function in capacities of urban development,agricultural production,and ecological conservation,among many others.Research of land space utilization efficiency(LSUE)and coupling coordination relationships among its subsystems are significant for sustainable land space development.In this study,taking the Urban Agglomeration in the Middle Reaches of the Yangtze River(UAMRYR)as the study area,we establish a measurement index system to evaluate the LSUE(2000–2018)and analyze its coupling coordination degree by utilizing an improved coupling coordination model.The main results include the following.(1)The average efficiency levels of urban space and agricultural space in the UAMRYR increased 2000–2018,while the average efficiency of ecological space declined.(2)The spatial pattern of the LSUE values varied greatly,with the distributions of high-efficiency and low-efficiency levels significantly different.(3)The coupling degree of LSUE includes three types,i.e.,high-level coupling,break-in,and antagonism.Each coupling degree type was characterized by change over time.(4)The proportion of areas with high coupling coordination and moderate coupling coordination increased from 2000 to 2018,while the proportion of areas with basic coupling coordination,moderate imbalance,and serious imbalance declined during this period.Given that the spatial differentiation of the LSUE and its coupling coordination,it is necessary to implement a differential land space development strategy in the UAMRYR.This study is helpful to promote the efficient utilization and coordinated development of land space utilization systems.
基金supported by the National Key R & D Program of China (Grants No. 2018YFC1507200)the National Natural Science Foundation of China (Grants Nos. 41505038, 91637211, 41775046 & 41575045)。
文摘Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body temperature(TBB) dataset during May to August 2000–2016(except 2005). The MCSs were divided into eastward-propagating(EP) and quasi-stationary(QS) types, to compare their spatial and temporal distributions and convective intensities, and to identify the favorable synoptic conditions for the formation and evolution of EP MCSs. The results showed that both MCS types occurred most often in July. The EP MCSs were mainly initiated over the eastern regions of the study area, while the QS type mainly originated in the western regions of the study area. Both MCS types mainly formed in the afternoon, but a second peak occurred in the early morning for QS MCSs. The EP MCSs had a larger cloud area at their mature stage and a lower cloud brightness temperature, indicating more intense convection. Additionally, the longer lifetime and further eastward propagation of the EP MCSs meant that they had a great influence on the precipitation over the middle and lower reaches of the Yangtze River. Synoptic circulation analysis demonstrated that the combination of the mid-level low trough east of the Tibetan Plateau(TP), and the western pacific subtropical high(WPSH), favored the formation and eastward propagation of EP MCSs. The positive vertical relative vorticity and stronger vertical wind shear provided dynamic conditions favorable for convective organization and development. Furthermore, a stronger low level jet imported warm and moist air to the eastern edge of, and the regions east of, the second-step terrain. The substantial convergence of water vapor promoted the development and long-lived maintenance of the EP MCSs.
基金Supported by the National Key Basic Research and Development(973)Program of China(2012CB417201)
文摘To investigate the multi-scale features in two persistent heavy rainfall(PHR) events in the middle and lower reaches of the Yangtze River(MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale oscillations in the north and south of 30?N on the PHR events by performing sensitivity experiments with the Weather Research and Forecast(WRF) model. It is found that the 60-day lowpass perturbation made a trivial contribution to the MLRYR precipitation during the PHR event in 1982.This PHR event resulted mainly from the combined effects of 30–60-day oscillation at low latitudes and10–30-day oscillation at both high and low latitudes. The southwesterly anomalies associated with the 30–60-day anticyclonic anomaly over the northwestern Pacific facilitated moisture transport from the ocean to the MLRYR and enhanced the low-level convergence and ascending motion in the MLRYR. This similarly occurred in the 10–30-day oscillation as well. Moreover, the 10–30-day anomalies at high latitudes played a role in strengthening the large-scale low-level convergence over the MLRYR. The PHR event in 1998 was mainly related to the 60-day oscillation at both high and low latitudes and 30–60-day oscillation at low latitudes. The 60-day low-pass filtered anomalous cyclone at high latitudes in the north of 30?N contributed to the development of low-level convergence and ascending motion in northern MLRYR while the anomalous anticyclone at low latitudes in the south of 30?N not only increased the moisture in the MLRYR but also preconditioned the dynamical factors favorable for PHR over the whole area. The 30–60-day perturbations located north and south of 30?N worked together producing positive moisture anomaly in the MLRYR.In addition, the anomalous circulation in the south of 30?N tended to favor the development of ascending motion and low-level convergence in the MLRYR.
基金National Natural Science Foundation of China(41375138,41305120,41275151)Natural Science Foundation of Jiangsu Province,China(BK20130988)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education(20133228120002)Graduate Student Innovation Plan at the Universities of Jiangsu province(N0782002211)
文摘Based on data of radiation fog events in Xuanen, Hubei province, 2010, this paper analyzes the microphysical process and evolution characteristics of radiation fogs with complicated substrate in the upper and middle reaches of the Yangtze River, and compares them with findings in other areas. Results are as follows: radiation fog in Xuanen is evidently weaker in droplet number concentration and liquid water content than land fogs in other areas. Its liquid water content fluctuates obviously, 0.01g/m3 with visibility of 1,000 meters, which is quite different from that in urban areas, but similar to the Nanling Mountains. Bi-modal droplet distribution is likely to occur in Xuanen mountain radiation fog(MRF) events. Statistical analysis shows that the observed droplet size distribution can be piecewise described well by the Gamma distribution. There is a positive correlation between liquid water content, fog droplet concentration and mean radius, especially in the development and dissipation stage. Condensation growth and droplet evaporation are major processes of Xuanen MRF. The dissipation time coincided with the time when the grass temperature reached the peak value, which indicated that dew evaporation is a key role in maintaining Xuanen MRF. In the early stage of dense fog's growth, droplets with diameter of over 20 micrometers can be observed with visibility of800-1,000 m, which might be caused by the transportation of low cloud droplets to earth's surface by turbulence. Big droplets in the initial stage correspond to higher water content, leading to the higher observed value of water content of Xuanen MRF.
基金supported by the National Key R&D Program of China(Grant Nos.2019YFA0708602,2019YFA0708603,and 2016YFC0600201)the National Natural Science Foundation of China(Grant Nos.42130807,42074099)the China Geological Survey(Grant No.1212011220243)。
文摘To investigate the geodynamic processes of Mesozoic large-scale mineralization in South China,we deployed a 350-km-long,wide-angle seismic reflection/refraction sounding profile between Yingshan in Hubei and Changshan in Zhejiang.This profile traverses the Cu-Au metallogenic belt in the middle and lower reaches of the Yangtze River(YMB),the Jiangnan W-polymetal metallogenic belt(JNMB),and the Qinhang Cu-polymetal metallogenic belt(QHMB).Our imaging results reveal various interesting velocity features along the profile.(1)The velocity structure is characterized by vertical layering and horizontal blocking;(2)the YMB is marked by high velocity and high V_(p)/V_(s) ratios in general with a significantly uplifted Moho interface and a thin crust of~31 km,and the lower crust contains high-velocity anomalies and has the characteristics of a crustmantle transition zone;(3)the JNMB is bounded by the Jiangnan fault and Jingdezhen-Huangshan fault and has low-velocity anomalies and low V_(p)/V_(s) ratios;and(4)the QHMB is characterized by high-velocity anomalies and high V_(p)/V_(s) ratios.The highvelocity anomalies in the YMB and QHMB represent relatively Cu-Au-rich mafic juvenile lower crust.The formation of this kind of crust is considered to be related to mantle-derived magma underplating or residues of Neoproterozoic oceanic crustal materials,and it also provided sources for large-scale Cu-Au mineralization in the Mesozoic.The JNMB has features similar to those of ancient crusts enriched in W-Sn,the partial melting of which played a leading role in the formation of the superlarge W deposits in this belt.Considering these results and other regional geological data,we propose that a large-scale oblique upwelling of the asthenosphere along the collisional belt of the Yangtze and Cathaysia blocks during the Mesozoic was the deep driving mechanism for the explosive mineralization of Cu,Au,and W in northeastern South China.The boundaries of the blocks or terrains and discontinuities of the lithosphere were the main channels for deep heat and magmas and therefore controlled the spatial distribution of the metallogenic belt.
基金National Natural Science Foundation of China,No.52279066Fundamental Research Funds for Central Welfare Research Institutes,No.TKS20190406Follow-up Scientific Research Project of the Three Gorges Project,No.SXHXGZ-2022-1。
文摘Given the importance of waterway depths in river development,the effects of the evolution of bars and troughs on waterway expansion play an important role in river management and water depth conservation.This study aims to expand the waterway dimensions of the Jingjiang Reach of the Yangtze River.To achieve this objective,determining the relationship between river evolution processes and the potential for waterway depth improvement and navigation hindrances is vital.Therefore,the sedimentation,hydrological,and terrain data of the Jingjiang Reach from 1955 to 2020 are analysed to elucidate the above-mentioned relationship.Since the commissioning of the Three Gorges Dam,the scouring of the low-flow channel has accounted for 90%-95%of all scouring in the Jingjiang Reach.Furthermore,the central bars and beaches have shrunk by 9.4%and 24.9%,respectively,and 18.3%overall.Considering the bed scouring and waterway regulation projects in the Jingjiang Reach,we investigated the continuity of a 4.5 m×200 m×1050 m(depth×width×bend radius)waterway along the Jingjiang Reach,and find that navigation-hindering channels account for over 5.3%of the waterway length.Furthermore,part of the Jingjiang Reach is an important nature reserve and shelters numerous water-related facilities,which inhibits the implementation of waterway deepening projects.The findings of this study demonstrate that numerous challenges are associated with increasing the waterway depths of the Jingjiang Reach.
基金National Key Research and Development Program of China,No.2018YFB1600400Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,No.2017491211Fundamental Research Funds for Central Welfare Research Institutes,No.TKS20200312。
文摘The operation of large-scale reservoirs have modified water and sediment transport processes,resulting in adjustments to the river topography and water levels.The polynomial fitting method was applied to analyze the variation characteristics of water levels under different water discharge values in the Jingjiang reach of the Yangtze River from 1991–2016.The segregation variable method was used to estimate the contributions of the varied riverbed evaluation,the downstream-controlled water level,and the comprehensive roughness on the altered water level at an identical flow.We find that low water levels in the Jingjiang reach of the Yangtze River from 1991–2016 are characterized by a significant downward trend,which has intensified since 2009.Riverbed scouring has been the dominate factor causing the reduced low water level while increased roughness alleviated this reduction.From 1991–2016,there was first a decrease followed by an increase in the high water level.The variation characteristic in terms of the'high flood discharge at a high water level'before 2003 transformed into a'middle flood discharge at a high water level'since 2009.The increased comprehensive roughness was the main reason for the increased high water level,where river scouring alleviated this rise.For navigation conditions and flood control,intensified riverbed scouring of the sandy reaches downstream from dams enhanced the effects that the downstream water level has on the upstream water level.This has led to an insufficient water depth in the reaches below the dams,which should receive immediate attention.The alteredvariation characteristics of the high water level have also increased the flood pressure in the middle reaches of the Yangtze River.
基金National Natural Science Foundation of China,No.42001187,No.41701629。
文摘The spatial relationships between traffic accessibility and supply and demand(S&D)of ecosystem services(ESs)are essential for the formulation of ecological compensation policies and ESs regulation.In this study,an ESs matrix and coupling analysis method were used to assess ESs S&D based on land-use data for 2000,2010,and 2020,and spatial regression models were used to analyze the correlated impacts of traffic accessibility.The results showed that the ESs supply and balance index in the middle reaches of the Yangtze River urban agglomeration(MRYRUA)continuously decreased,while the demand index increased from 2000 to 2020.The Gini coefficients of these indices continued to increase but did not exceed the warning value(0.4).The coupling degree of ESs S&D continued to increase,and its spatial distribution patterns were similar to that of the ESs demand index,with significantly higher values in the plains than in the montane areas,contrasting with those of the ESs supply index.The results of global bivariate Moran’s I analysis showed a significant spatial dependence between traffic accessibility and the degree of coupling between ESs S&D;the spatial regression results showed that an increase in traffic accessibility promoted the coupling degree.The present results provide a new perspective on the relationship between traffic accessibility and the coupling degree of ESs S&D,representing a case study for similar future research in other regions,and a reference for policy creation based on the matching between ESs S&D in the MRYRUA.
基金National Natural Science Foundation of China(42171411)Youth Innovation Promotion Association,CAS(2019055)。
文摘Since the launch of China’s reform and opening up policy,the process of urbanization in China has accelerated significantly.With the development of cities,inter-city interactions have become increasingly close,forming urban agglomerations that tend to be integrated.Urban agglomerations are regional spaces with network relationships and hierarchies,and have always been the main units for China to promote urbanization and regional coordinated development.In this paper,we comprehensively consider the network and hierarchical characteristics of an urban agglomeration,while using urban flow to describe the interactions of the inter-city networks and the hierarchical generalized linear model(HGLM)to reveal the hierarchical driving mechanism of the urban agglomeration.By coupling the HGLM with a cellular automata(CA)model,we introduced the HGLM-CA model for the simulation of the spatial expansion of an urban agglomeration,and compared the simulation results with those of the logistic-CA model and the biogeography-based optimization CA(BBO-CA)model.According to the results,we further analyzed the advantages and disadvantages of the proposed HGLM-CA model.We selected the middle reaches of the Yangtze River in China as the research area to conduct this empirical research,and simulated the spatial expansion of the urban agglomeration in 2017 on the basis of urban land-use data from 2007 and 2012.The results indicate that the spatial expansion of the urban agglomeration can be attributed to various driving factors.As a driving factor at the urban level,urban flow promotes the evolution of land use in the urban agglomeration,and also plays an important role in regulating cell-level factors,making the cell-level factors of different cities show different driving effects.The HGLM-CA model is able to obtain a higher simulation accuracy than the logistic-CA model,which indicates that the simulation results for urban agglomeration expansion considering urban flow and hierarchical characteristics are more accurate.When compared with the intelligent algorithm model,i.e.,BBO-CA,the HGLM-CA model obtains a lower simulation accuracy,but it can analyze the interaction of the various driving factors from a hierarchical perspective.It also has a strong explanatory effect for the spatial expansion mechanism of urban agglomerations.
基金National Natural Science Foundation of China,No.42001187,No.41701629。
文摘The continuous degradation of ecosystem services is an important challenge faced by the world.Improvements in transportation infrastructure have had substantial impacts on economic development and ecosystem services.Exploring the influence of traffic accessibility on ecosystem services can delay or stop their deterioration;however,studies on its impact are lacking.This study addresses this gap by analysing the impact of traffic accessibility on ecosystem services using an integrated spatial regression approach based on an evaluation of the ecosystem services value(ESV)and traffic accessibility in the Middle Reaches of the Yangtze River Urban Agglomeration(MRYRUA)in China.The results indicated that the ESV in the MRYRUA continuously decreased during the study period,and the average ESV in plain areas,areas surrounding the core cities,and areas along the main traffic routes was significantly lower than that in areas along the Yangtze River and the surrounding mountainous areas.Traffic accessibility continued to increase during the study period,and the high-value areas centred on Wuhan,Changsha,Nanchang,and Yichang were radially distributed.The global bivariate spatial autocorrelation coefficient between the average ESV and traffic accessibility was negative.The average ESV and traffic accessibility exhibited significant spatial dependence and spatial heterogeneity.Spatial regression also proved that there was a negative association between the average ESV and traffic accessibility,and scale effects were evident.The findings of this study have important policy implications for future ecological protection and transportation planning.
