Water use efficiency(WUE),as a pivotal indicator of the coupling degree within the carbon–water cycle of ecosystems,holds considerable importance in assessment of the carbon–water balance within terrestrial ecosyste...Water use efficiency(WUE),as a pivotal indicator of the coupling degree within the carbon–water cycle of ecosystems,holds considerable importance in assessment of the carbon–water balance within terrestrial ecosystems.However,in the context of global warming,WUE evolution and its primary drivers on the Tibetan Plateau remain unclear.This study employed the ensemble empirical mode decomposition method and the random forest algorithm to decipher the nonlinear trends and drivers of WUE on the Tibetan Plateau in 2001–2020.Results indicated an annual mean WUE of 0.8088 gC/mm·m^(2)across the plateau,with a spatial gradient reflecting decrease from the southeast toward the northwest.Areas manifesting monotonous trends of increase or decrease in WUE accounted for 23.64%and 9.69%of the total,respectively.Remarkably,66.67%of the region exhibited trend reversals,i.e.,39.94%of the area of the Tibetan Plateau showed transition from a trend of increase to a trend of decrease,and 26.73%of the area demonstrated a shift from a trend of decrease to a trend of increase.Environmental factors accounted for 70.79%of the variability in WUE.The leaf area index and temperature served as the major driving forces of WUE variation.展开更多
To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the...To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.展开更多
Although the factors affecting rural-to-urban migration have been discussed and analyzed in detail, few studies have examined the spatiotemporal dynamic characteristics of rural migrants’ employment and working-citie...Although the factors affecting rural-to-urban migration have been discussed and analyzed in detail, few studies have examined the spatiotemporal dynamic characteristics of rural migrants’ employment and working-cities in the post-immigrate era, which is essential for the citizenization and social integration of new-type urbanization in China. This study uses survey data from rural migration laborers across the eastern, central, and western China to construct a comprehensive labor migration stability index, and compares the determinants of the migration stability of rural labor among cities and industries using Geodetector. The results are as follows: 1) Compared with the midwestern cities, eastern cities have attracted younger and more skilled rural labor, and industries with higher technical content have higher migration stability among rural laborers. 2) Rural laborers more often adapt to changes by changing employment instead of changing working-cities. 3) The individual experiences of rural laborers and urban characteristics have significant impacts on the stability of migration, and family and societal guanxi(Chinese interpersonal relationships) enhance migration stability. 4) A unified labor market and convenient transportation have somewhat slowed industrial transfers and labor backflow. This study enhances our understanding of the roles of industrial transfer and new-type urbanization in shaping the labor geography landscape and provides policy implications for the promotion of people-oriented urbanization.展开更多
Strata in red bed areas have typical characteristics of soft-hard interbedding and high sensitivity to water. Under the comprehensive action of internal stratigraphic structure and external hydrological factors, red b...Strata in red bed areas have typical characteristics of soft-hard interbedding and high sensitivity to water. Under the comprehensive action of internal stratigraphic structure and external hydrological factors, red bed landslides have highly complex spatiotemporal characteristics, presenting significant challenges to the prevention and control of landslide disasters in red bed areas, especially for slope and tunnel engineering projects. In this study, we applied an interdisciplinary approach combining small baseline subset interferometric synthetic aperture radar(SBAS-InSAR), deep displacement monitoring, and engineering geological surveying to identify the deformation mechanisms and spatiotemporal characteristics of the Abi landslide, an individual landslide that occurred in the red bed area of Western Yunnan, China. Surface deformation time series indicated that a basic deformation range developed by March 2020. Based on In SAR results and engineering geological analysis, the landslide surface could be divided into three zones: an upper sliding zone(US), a lower uplifted zone(LU), and a toe zone(Toe). LU was affected by the structure of the sliding bed with variable inclination. Using deep displacement curves combined with the geological profile, a set of sliding surfaces were identified between different lithology. The groundwater level standardization index(GLSI) and deformation normalization index(DNI) showed different quadratic relationships between US and LU. Verification using the Pearson correlation analysis shows that the correlation coefficients between model calculated results and measured data are 0.7933 and 0.7577, respectively, indicating that the DNI-GLSI models are applicable. A fast and short-lived deformation sub stage(ID-Fast) in the initial deformation stage was observed, and ID-Fast was driven by concentrated rainfall.展开更多
In the paper,daily near-surface wind speed data from 462 stations are used to study the spatiotemporal characteristics of the annual and seasonal mean wind speed(MWS)and effective wind energy density(EWED)from 1960 to...In the paper,daily near-surface wind speed data from 462 stations are used to study the spatiotemporal characteristics of the annual and seasonal mean wind speed(MWS)and effective wind energy density(EWED)from 1960 to 2016,through the methods of kriging interpolation,leastsquares,correlation coefficient testing,and empirical orthogonal function(EOF)analysis.The results show that the annual MWS is larger than 3 m s-1 and the EWED is larger than 75 W m-2 in northern China and parts of coastal areas.However,the MWS and EWED values in southern China are all smaller than in northern China.Over the past 50 years,the annual and seasonal MWS in China has shown a significant decreasing trend,with the largest rate of decline in spring for northern China and winter for coastal areas.The annual MWS in some areas of Guangdong has an increasing trend,but it shows little change in southwestern China,South China,and west of Central China.Where the MWS is high,the rate of decline is also high.The main spatial distributions of the annual MWS and the annual EWED show high consistency,with a decreasing trend year by year.The decreasing trend of wind speed and wind energy resources in China is mainly related to global warming and land use/cover change.展开更多
In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and watervapor flux divergence in different seasons over northeast China and the water balance of that area...In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and watervapor flux divergence in different seasons over northeast China and the water balance of that area. The data used in this paper is provided by the European Center for Medium-Range Weather Forecasts （ECMWF）. The results show that the spatial distributions of precipitable water, precipitation, and evaporation feature that the values of elements above in the southeastern area are larger than those in the northwestern area; in summer, much precipitation and evaporation occur in the Changbai Mountain region as a strong moisture convergence region; in spring and autumn, moisture divergence dominates the northeast of China; in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons changed in a truly imperceptible way. In spring, the evaporation exceeded the precipitation in northeast China; in summer, the precipitation was more prominent; in autumn and winter, precipitation played a more dominating role than the evaporation in the northern part of northeast China, while the evaporation exceeded the precipitation in the southern part. The Interim ECMWF Re-Analysis （ERA-Interim） data have properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA- Interim data can be used in the research of water balance in northeast China. On a seasonal scale, the moisture convergence has a greater influence than the local moisture variation on a moisture sink, and the latter is variable slightly, generally as a constant. Likewise, in different seasons, the total precipitation has a much greater influence than the evaporation on the moisture sink.展开更多
Glaciers provide essential resources and services for human well-being and socio-economic development in arid regions.It is of great significance for regional socioeconomic sustainable development and environmental pr...Glaciers provide essential resources and services for human well-being and socio-economic development in arid regions.It is of great significance for regional socioeconomic sustainable development and environmental protection to conduct a glacier service value assessment and to analyze its spatiotemporal characteristics.Based on the first and second Chinese glacier inventories of the Qilian Mountains,a glacier service value evaluation system was established.Then the glacier service value and its spatiotemporal variation were assessed by combining the methods of unit area service price,value equivalent factor,and the glacier service value change index(GSCI).Three key results were obtained.(1)The total service value of glaciers in the Qilian Mountains for 2016 was 24.354 billion yuan.The main services provided were climate regulation and runoff regulation,which accounted for 60.58%and 33.14%of the total service value,respectively.Minor services were freshwater supply and hydropower,which accounted for 3.47%and 1.75%of the total value,respectively.The value of other types of services was about 0.259 billion yuan.(2)Among the various river systems in the Qilian Mountains,the Shule River basin had the highest glacier service value(7.771 billion yuan,31.91%),followed by the Haltang River basin(4.321 billion yuan,17.74%)and the Beida River basin(3.281 billion yuan,13.47%).In terms of administrative divisions,the glacier service value of the Qilian Mountains in Qinghai Province was 1.138 billion yuan higher than that of Gansu Province at 11.608 billion yuan,of which the services in the Haixi Mongol and Tibetan Autonomous Prefecture and Jiuquan City were valued at 11.124(45.68%)and 7.758(31.86%)billion yuan,respectively.(3)During the period from 1956 to 2010,the service value of glaciers in the Qilian Mountains declined by 435 million yuan,with an acceleration in the decreasing trend from west to east.展开更多
A high-resolution customized numerical model is used to analyze the water transport in the three major water passages between the Andaman Sea(AS)and the Bay of Bengal,i.e.,the Preparis Channel(PC),the Ten Degree Chann...A high-resolution customized numerical model is used to analyze the water transport in the three major water passages between the Andaman Sea(AS)and the Bay of Bengal,i.e.,the Preparis Channel(PC),the Ten Degree Channel(TDC),and the Great Channel(GC),based on the daily averaged simulation results ranging from 2010 to 2019.Spectral analysis and Empirical Orthogonal Function(EOF)methods are employed to investigate the spatiotemporal variability of the water exchange and controlling mechanisms.The results of model simulation indicate that the net average transports of the PC and GC,as well as their linear trend,are opposite to that of the TDC.This indicates that the PC and the GC are the main inflow channels of the AS,while the TDC is the main outflow channel of the AS.The transport variability is most pronounced at surface levels and between 100 m and 200 m depth,likely affected by monsoons and circulation.A 182.4-d semiannual variability is consistently seen in all three channels,which is also evident in their second principal components.Based on sea level anomalies and EOF analysis results,this is primarily due to equatorial winds during the monsoon transition period,causing eastward movement of Kelvin waves along the AS coast,thereby affecting the spatiotemporal characteristics of the flow in the AS.The first EOF of the PC flow field section shows a split at 100 m deep,likely due to topography.The first EOF of the TDC flow field section is steady but has potent seasonal oscillations in its time series.Meanwhile,the first EOF of the GC flow field section indicates a stable surface inflow,probably influenced by the equatorial Indian Ocean’s eastward current.展开更多
N170 is a negative event-related potential(ERP)component in response to visual stimuli,such as faces.It remains controversial whether N170 reflects the specific processing of faces or can also be elicited by objects o...N170 is a negative event-related potential(ERP)component in response to visual stimuli,such as faces.It remains controversial whether N170 reflects the specific processing of faces or can also be elicited by objects of expertise(e.g.,words).In this research,we conducted a meta-analysis for the spatiotemporal characteristics of N170 of face and word stimuli from 24 studies in which both stimuli were presented for each subject.We observed that(1)both face and word stimuli can elicit conspicuous N170s and that there was no difference between the amplitude of face-N170 and word-N170;(2)there is no difference in the latencies between the two N170s;and(3)both N170s are distributed in the occipitotemporal regions but with a reversed hemispheric distribution pattern-faceN170 is more negative in the right than left occipitotemporal regions,while word-N170 is the opposite.These results showed that the face-and word-N170s are qualitatively the same but have different hemispheric lateralization advantages-N170 might be a general neural index of the expertise-dependent object-recognition process in occipitotemporal regions.展开更多
The size of compression gratings has become a crucial factor in achieving 100-PW level super-intense ultrafast lasers,in view of the laser-induced damage of grating compressor.To improve the output laser energy within...The size of compression gratings has become a crucial factor in achieving 100-PW level super-intense ultrafast lasers,in view of the laser-induced damage of grating compressor.To improve the output laser energy within the damage threshold of grating compressor and therefore obtain higher laser peak power,we proposed the full-aperture grating compressor(FAGC).In this work,the spatiotemporal characteristics of the output pulses from FAGC are investigated,based on the SULF-10 PW laser facility with~400-mm beam diameter.The simulation and proof-of-principle experiment show that the pulse duration and the focusing quality of the output pulses from an FAGC are basically identical with those from a conventional 4-grating compressor;meanwhile,no evident diffractions are induced by the spectral clipping of FAGC.Thus,there is no marked influence of FAGC on the spatiotemporal characteristics of output compressed pulses.This work further demonstrates the feasibility of FAGC efficiently,which should be a promising scheme for realizing single-channel 100-PW level super-intense ultrafast lasers.展开更多
Understanding the coupling relationship between ecosystem services and poverty livelihoods is a prerequisite for poverty eradication and ecological protection in China.In this paper,we intended to quantify the couplin...Understanding the coupling relationship between ecosystem services and poverty livelihoods is a prerequisite for poverty eradication and ecological protection in China.In this paper,we intended to quantify the coupling relationship between ecosystem services and poverty livelihoods in 717 poverty-stricken counties in China.First,we identified distinct levels of ecosystem services and poverty respectively in the poverty-stricken areas based on the ecosystem services subsystem index and poverty livelihoods subsystem index.Then,we calculated the coupling degree and coupling coordination degree between the ecosystem services and the poverty livelihoods in China^poverty-stricken counties from 2000 to 2015.Finally,we analyzed the temporal and spatial evolution of the coupling between ecosystem services and poverty livelihoods.The results indicate that the ecosystem services showed a trend of first decreasing and then increasing,while the poverty level showed an increased trend.In addition,the coupling relationship between ecosystem services and poverty livelihoods in poverty-stricken counties was also improved from 2000 to 2015.However,the coupling degree value or coupling coordination degree values in some counties or contiguous impoverished areas showed a decreased trend,the coupling relationship between ecosystem services and poverty livelihoods in those counties or areas was higher conflict.Future more,the coupling relationship in China's poverty-stricken counties was mainly intermediate conflict and low conflict,which need to improve in the future.Thus,it is suggested that effective measures are required to lift ecosystem services out of the poverty trap and into sustainable livelihoods.展开更多
Precipitable Water Vapor(PWV),as an important indicator of atmospheric water vapor,can be derived from Global Navigation Satellite System(GNSS)observations with the advantages of high precision and all-weather capacit...Precipitable Water Vapor(PWV),as an important indicator of atmospheric water vapor,can be derived from Global Navigation Satellite System(GNSS)observations with the advantages of high precision and all-weather capacity.GNSS-derived PWV with a high spatiotemporal resolution has become an important source of observations in mete-orology,particularly for severe weather conditions,for water vapor is not well sampled in the current meteorological observing systems.In this study,an empirical atmospheric weighted mean temperature(Tm)model for Guilin is estab-lished using the radiosonde data from 2012 to 2017.Then,the observations at 11 GNSS stations in Guilin are used to investigate the spatiotemporal features of GNSS-derived PWV under the heavy rainfalls from June to July 2017.The results show that the new Tm model in Guilin has better performance with the mean bias and Root Mean Square(RMS)of−0.51 and 2.12 K,respectively,compared with other widely used models.Moreover,the GNSS PWV estimates are validated with the data at Guilin radiosonde station.Good agreements are found between GNSS-derived PWV and radiosonde-derived PWV with the mean bias and RMS of−0.9 and 3.53 mm,respectively.Finally,an investigation on the spatiotemporal characteristics of GNSS PWV during heavy rainfalls in Guilin is performed.It is shown that variations of PWV retrieved from GNSS have a direct relationship with the in situ rainfall measurements,and the PWV increases sharply before the arrival of a heavy rainfall and decreases to a stable state after the cease of the rainfall.It also reveals the moisture variation in several regions of Guilin during a heavy rainfall,which is significant for the moni-toring of rainfalls and weather forecast.展开更多
The spatiotemporal characteristics of bridge deck runoff under a natural rainfall event are explored. The Taizhou Bridge is taken as a study case,and a hydrodynamic model based on the two-dimensional shallow water equ...The spatiotemporal characteristics of bridge deck runoff under a natural rainfall event are explored. The Taizhou Bridge is taken as a study case,and a hydrodynamic model based on the two-dimensional shallow water equations is used to analyze the runoff characteristics. The results indicate that the runoff velocity rate and depth are positively related to rainfall intensity,yet they have different response degrees to it. The inlet’s effect degree on lane water film has a positive relationship with rainfall intensity. A natural logarithm function( R^2= 0.706) can illustrate this relationship. However,the inlet’s effect degree on ponding at the curb shows a negative relationship with the rainfall intensity. A negative exponential function( R^2= 0.824) can reveal this relationship. With the decrease in the longitudinal slope SL,the ponding depth at the curb increases significantly at the bridge approach slab,whereas the lane water film thickness( WFT) is almost unchanged,but the lane WFT increases greatly at the location with the minimum longitudinal slope. It is concluded that the characteristics of the bridge deck runoff present apparent spatiotemporal differences,the inlet ’s effects on bridge deck runoff are quantitatively correlated with rainfall intensity, and the effective drainage measures are necessary for the bridge approach slab.展开更多
Tropical cyclone activity has undergone significant changes under the impact of global warming since the 20th century.However,the characteristic and trend changes of landfalling tropical cyclones over China still need...Tropical cyclone activity has undergone significant changes under the impact of global warming since the 20th century.However,the characteristic and trend changes of landfalling tropical cyclones over China still need to be further clarified.The study conducted an analysis of the spatiotemporal characteristics and trends of landfalling tropical cyclones over China from 1949 to 2022 using the dataset of the best tracks of tropical cyclones from the China Meteorological Administration.Additionally,we explored the influences of ENSO and the Pacific Decadal Oscillation(PDO)on landfalling tropical cyclone activities.The results indicate that:(1)The annual average number of landfalling tropical cyclones over China is approximately 8.85,showing a significant decreasing trend,and the decreasing range becomes larger with lower latitude overall.However,both the proportion of landfalling tropical cyclones to the total number and the percentage of higher intensity tropical cyclones increase.(2)The landfall locations of tropical cyclones in China are mainly concentrated between 18°N and 26°N,accounting for approximately 88.2%of the total,and the landfall frequency shows a sharp decline in the regions north of 30°N.The central landfall location of tropical cyclones has shifted significantly northwestward,moving closer to China.Compared to 1949–1969,the central genesis location from 2010 to 2022 shifted 4.5°westward and 2.0°northward.(3)There is a correlation between ENSO and the genesis frequency variation of tropical cyclones in the Northwest Pacific and landfalling over China.El Ni?o promotes the genesis of strong tropical cyclones and leads to a more southeastern bias in the genesis location of landfalling tropical cyclones,while La Ni?a has an opposite effect.The PDO also affects the tropical cyclones to a certain extent.During the PDO warm phase,the genesis position of tropical cyclones is westward and the number is smaller than that in the cold phase.This study further clarifies the changing trends and characteristics of landfalling tropical cyclones over China since 1949.It also highlights the impacts of ENSO and the PDO on tropical cyclone activities.The findings can serve as a scientific basis for conducting simulations and assessments of tropical cyclones and for disaster prevention and mitigation efforts.展开更多
A holistic and precise assessment of retaining wall deformations is critical for on-site risk management of large combined deep excavation projects,where the risk-related points are highly dispersed,evolving,and inter...A holistic and precise assessment of retaining wall deformations is critical for on-site risk management of large combined deep excavation projects,where the risk-related points are highly dispersed,evolving,and interacting.Despite extensive exploration of this topic in previous studies,the omission of intricate spatiotemporal characteristics of wall deformations has resulted in diminished prediction accuracy and stability.To mitigate this deficiency,a spatiotemporal characteristics matrix for all data points and time series was first generated for a deep excavation scenario and used as input for a new hybrid model that combines convolutional neural network(CNN)and long short-term memory(LSTM)with incorporated attention mechanism(CNN-LSTM-Att),which enables the cross-learning mechanism and improves interpretability.In addition,by leveraging the attention weight,a new risk assessment index for retaining wall deformations across various scenarios was formulated.Then the proposed method was applied in a large combined deep excavation in Shanghai,China.The results show that:(1)The incorporation of fedin characteristic data and the attention mechanism enables the proposed method to produce satisfactory prediction results for the holistic spatiotemporal distribution of a large combined excavation;(2)Compared with other published models,the proposed model shows much better prediction accuracy,interpretability,and stability,especially in medium-and long-term predictions;and(3)The new risk assessment index serves as a reliable decision-making tool for assessing the risk evolution of retaining wall deformations and provides valuable guidance for effective risk management in multi-scenario excavation projects.展开更多
Using complex network methods,we construct undirected and directed heatwave networks to systematically analyze heatwave events over China from 1961 to 2023,exploring their spatiotemporal evolution patterns in differen...Using complex network methods,we construct undirected and directed heatwave networks to systematically analyze heatwave events over China from 1961 to 2023,exploring their spatiotemporal evolution patterns in different regions.The findings reveal a significant increase in heatwaves since the 2000s,with the average occurrence rising from approximately 3 to 5 times,and their duration increasing from 15 to around 30 days,nearly doubling.An increasing trend of“early onset and late withdrawal”of heatwaves has become more pronounced each year.In particular,eastern regions experience heatwaves that typically start earlier and tend to persist into September,exhibiting greater interannual variability compared to western areas.The middle and lower reaches of the Yangtze River and Xinjiang are identified as high-frequency heatwave areas.Complex network analysis reveals the dynamics of heatwave propagation,with degree centrality and synchronization distance indicating that the middle and lower reaches of the Yangtze River,Northeast China,and Xinjiang are key nodes in heatwave spread.Additionally,network divergence analysis shows that Xinjiang acts as a“source”area for heatwaves,exporting heat to surrounding regions,while the central region functions as a major“sink,”receiving more heatwave events.Further analysis from 1994 to 2023 indicates that heatwave events exhibit stronger network centrality and more complex synchronization patterns.These results suggest that complex networks provide a refined framework for depicting the spatiotemporal dynamics of heatwave propagation,offering new avenues for studying their occurrence and development patterns.展开更多
The spatiotemporal characteristics of hydrothermal resources in southern rice production area of China have changed under the background of climate change,and this change would affect the effectiveness of hydrothermal...The spatiotemporal characteristics of hydrothermal resources in southern rice production area of China have changed under the background of climate change,and this change would affect the effectiveness of hydrothermal resources during local rice growing period.According to the cropping system subdivision in southern rice production area of China during 1980s,this study used climate data from 254 meteorological stations and phonological data from 168 agricultural observation stations in the south of China,and adopted 6 international evaluation indices about the effectiveness of hydrothermal resources to analyze the temporal and spatial characteristics of hydrothermal resources during the growing period of single cropping rice system and double cropping rice system for 16 planting zones in the whole study area.The results showed that：in southern rice production area of China,the effectiveness of thermal resources of single cropping rice area（SCRA） was less than that of double cropping rice area（DCRA）,whereas the effectiveness of thermal resources of both SARA and DCRA showed a decreasing trend.The index value of effective precipitation satisfaction of SCRA was higher than that of DCRA,nevertheless the index value of effective precipitation satisfaction of both SCRA and DCRA showed a decreasing trend.There was a significant linear relationship between effective thermal resource and water demand,likely water demand increased by 18 mm with every 100°C d increase of effective heat.Effective precipitation satisfaction index（EPSI） showed a negative correlation with effective heat,yet showed a positive correlation with effective precipitation.EPSI reduced by 1% when effective heat resource increased by 125°C d.This study could provide insights for policy makers,land managers or farmers to improve water and heat resource uses and rationally arrange rice production activities under global climate change condition.展开更多
Background:Biogenic volatile organic compounds(BVOCs)play an essential role in tropospheric atmospheric chemical reactions.There are few studies conducted on BVOCs emission of dominant forest species in the Jing-Jin-J...Background:Biogenic volatile organic compounds(BVOCs)play an essential role in tropospheric atmospheric chemical reactions.There are few studies conducted on BVOCs emission of dominant forest species in the Jing-Jin-Ji area of China.Based on the field survey,forest resources data and the measured standard emission factors,the Guenther model developed in 1993(G93)was applied in this paper to estimate the emission of BVOCs from several dominant forest species(Platycladus orientalis,Quercus variabilis,Betula platyphylla,Populus tomentosa,Pinus tabuliformis,Robinia pseudoacacia,Ulmus pumila,Salix babylonica and Larix gmelinii)in the Jing-Jin-Ji area in 2017.Then the spatiotemporal emission characteristics and atmospheric chemical reactivity of these species were extensively evaluated.Results:The results showed that the total annual BVOCs emission was estimated to be 70.8 Gg C·year^(−1),consisting 40.5%(28.7 Gg C·year^(−1))of isoprene,36.0%(25.5 Gg C·year^(−1))of monoterpenes and 23.4%(16.6 Gg C·year^(−1))of other VOCs.The emissions from Platycladus orientalis,Quercus variabilis,Populus tomentosa and Pinus tabulaeformis contributed 56.1%,41.2%,36.0% and 31.1%,respectively.The total BVOCs emission from the Jing-Jin-Ji area accounted for 61.9% and 1.8%in summer and winter,respectively.Up to 28.8% of emission was detected from Chengde followed by Beijing with 24.9%,that mainly distributed in the Taihang Mountains and the Yanshan Mountains.Additionally,the Robinia pseudoacacia,Populus tomentosa,Quercus variabilis,and Pinus tabulaeformis contributed mainly to BVOCs reaction activity.Conclusions:The BVOCs emission peaked in summer(June,July,and August)and bottomed out in winter(December,January,and February).Chengde contributed the most,followed by Beijing.Platycladus orientalis,Quercus variabilis,Populus tomentosa,Pinus tabulaeformis and Robinia pseudoacacia represent the primary contributors to BVOCs emission and atmospheric reactivity,hence the planting of these species should be reduced.展开更多
Owing to the expansion of the grid interconnection scale,the spatiotemporal distribution characteristics of the frequency response of power systems after the occurrence of disturbances have become increasingly importa...Owing to the expansion of the grid interconnection scale,the spatiotemporal distribution characteristics of the frequency response of power systems after the occurrence of disturbances have become increasingly important.These characteristics can provide effective support in coordinated security control.However,traditional model-based frequencyprediction methods cannot satisfactorily meet the requirements of online applications owing to the long calculation time and accurate power-system models.Therefore,this study presents a rolling frequency-prediction model based on a graph convolutional network(GCN)and a long short-term memory(LSTM)spatiotemporal network and named as STGCN-LSTM.In the proposed method,the measurement data from phasor measurement units after the occurrence of disturbances are used to construct the spatiotemporal input.An improved GCN embedded with topology information is used to extract the spatial features,while the LSTM network is used to extract the temporal features.The spatiotemporal-network-regression model is further trained,and asynchronous-frequency-sequence prediction is realized by utilizing the rolling update of measurement information.The proposed spatiotemporal-network-based prediction model can achieve accurate frequency prediction by considering the spatiotemporal distribution characteristics of the frequency response.The noise immunity and robustness of the proposed method are verified on the IEEE 39-bus and IEEE 118-bus systems.展开更多
Human-wildlife conflict(HWC)and its socioeconomic impacts are a pressing global issue.Accurately quantifying HWCs and their interaction with residential development is crucial for rural revitalization and biodiversity...Human-wildlife conflict(HWC)and its socioeconomic impacts are a pressing global issue.Accurately quantifying HWCs and their interaction with residential development is crucial for rural revitalization and biodiversity conservation efforts.This study investigates the interplay between rural residential expansion(RRE)with humanelephant conflict(HEC)in southern Yunnan Province using high-accuracy yearly land use/land cover data and Asian elephant accident data.A piecewise regression along with several metrics,including expansion intensity,rate of rural residential land,and residential density,were employed to analyze the spatial-temporal change characteristics of RRE.Then,a geographical detector and a bivariate spatial autocorrelation model were used to reveal the driving mechanisms of RRE,with particular emphasis on the spatial relations between RRE and HECs.The results indicate that HECs had a significant negative impact on RRE,exhibiting higher expansion intensity and rate of rural residential land in non-HEC areas than in HEC areas.High spatiotemporal consistency between accelerated RRE and intensified HECs occurred from 2010 onwards,which aligns with the year when the trend of settlement area expansion changed.RRE activities and ensuing land use conversions led to increased occurrences of HECs,which negatively affected the RRE.Compared to HECs,topography and locational factors exhibited a secondary effect on RRE activities.The findings underscore reciprocal feedback mechanisms between RRE and HECs and the elevated risk of adverse interactions between humans and elephants within the range of China’s wild elephants,providing theoretical support for coordinating conservation initiatives for Asian elephants with rural revitalization in the border areas of Southwest China.展开更多
基金National Nonprofit Institute Research Grant of CAF,No.CAFYBB2018ZA004,No.CAFYBB2023ZA009Fengyun Application Pioneering Project,No.FY-APP-ZX-2023.02。
文摘Water use efficiency(WUE),as a pivotal indicator of the coupling degree within the carbon–water cycle of ecosystems,holds considerable importance in assessment of the carbon–water balance within terrestrial ecosystems.However,in the context of global warming,WUE evolution and its primary drivers on the Tibetan Plateau remain unclear.This study employed the ensemble empirical mode decomposition method and the random forest algorithm to decipher the nonlinear trends and drivers of WUE on the Tibetan Plateau in 2001–2020.Results indicated an annual mean WUE of 0.8088 gC/mm·m^(2)across the plateau,with a spatial gradient reflecting decrease from the southeast toward the northwest.Areas manifesting monotonous trends of increase or decrease in WUE accounted for 23.64%and 9.69%of the total,respectively.Remarkably,66.67%of the region exhibited trend reversals,i.e.,39.94%of the area of the Tibetan Plateau showed transition from a trend of increase to a trend of decrease,and 26.73%of the area demonstrated a shift from a trend of decrease to a trend of increase.Environmental factors accounted for 70.79%of the variability in WUE.The leaf area index and temperature served as the major driving forces of WUE variation.
基金The National Natural Science Foundation of China(No.61171081,No.61471164)the Natural Science Foundation of Hunan Province(No.14JJ6043)
文摘To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.
基金the auspices of the National Natural Science Foundation of China(No.41471469)the Key Project of National Natural Science Found of China(No.41930651)Sichuan Provincial Research Center for Philosophy and Social Sciences-Sichuan Rural Development Research Center(No.CR1908)。
文摘Although the factors affecting rural-to-urban migration have been discussed and analyzed in detail, few studies have examined the spatiotemporal dynamic characteristics of rural migrants’ employment and working-cities in the post-immigrate era, which is essential for the citizenization and social integration of new-type urbanization in China. This study uses survey data from rural migration laborers across the eastern, central, and western China to construct a comprehensive labor migration stability index, and compares the determinants of the migration stability of rural labor among cities and industries using Geodetector. The results are as follows: 1) Compared with the midwestern cities, eastern cities have attracted younger and more skilled rural labor, and industries with higher technical content have higher migration stability among rural laborers. 2) Rural laborers more often adapt to changes by changing employment instead of changing working-cities. 3) The individual experiences of rural laborers and urban characteristics have significant impacts on the stability of migration, and family and societal guanxi(Chinese interpersonal relationships) enhance migration stability. 4) A unified labor market and convenient transportation have somewhat slowed industrial transfers and labor backflow. This study enhances our understanding of the roles of industrial transfer and new-type urbanization in shaping the labor geography landscape and provides policy implications for the promotion of people-oriented urbanization.
基金funded by the List of Key Science and Technology Projects in the Transportation Industry of the Ministry of Transport in 2021(Grant No.2021-MS4-105)the Science and Technology Project of Yunnan Traffic Planning Design Institute Co.,Ltd.(Grant No.ZL-2021-03)+7 种基金the Postgraduate Scientific Research Innovation Project of Yunnan University(Grant No.2020192)the National Key Research and Development Program of China(Grant No.2018YFC1504906)the National Natural Science Foundation of China(Grant No.41872251)the Plateau Mountain Ecology and Earth’s Environment Discipline Construction Project(Grant No.C1762101030017)the Joint Foundation Project between Yunnan Science and Technology Department and Yunnan University(Grants No.C176240210019 and 2019FY003017)the Yunnan Postdoctoral Foundation(Grant No.C615300504031)the China Geological Survey Project(Grant No.DD20221824)the science and technology innovation program of the department of transportation,Yunnan province,China(No.2019301)。
文摘Strata in red bed areas have typical characteristics of soft-hard interbedding and high sensitivity to water. Under the comprehensive action of internal stratigraphic structure and external hydrological factors, red bed landslides have highly complex spatiotemporal characteristics, presenting significant challenges to the prevention and control of landslide disasters in red bed areas, especially for slope and tunnel engineering projects. In this study, we applied an interdisciplinary approach combining small baseline subset interferometric synthetic aperture radar(SBAS-InSAR), deep displacement monitoring, and engineering geological surveying to identify the deformation mechanisms and spatiotemporal characteristics of the Abi landslide, an individual landslide that occurred in the red bed area of Western Yunnan, China. Surface deformation time series indicated that a basic deformation range developed by March 2020. Based on In SAR results and engineering geological analysis, the landslide surface could be divided into three zones: an upper sliding zone(US), a lower uplifted zone(LU), and a toe zone(Toe). LU was affected by the structure of the sliding bed with variable inclination. Using deep displacement curves combined with the geological profile, a set of sliding surfaces were identified between different lithology. The groundwater level standardization index(GLSI) and deformation normalization index(DNI) showed different quadratic relationships between US and LU. Verification using the Pearson correlation analysis shows that the correlation coefficients between model calculated results and measured data are 0.7933 and 0.7577, respectively, indicating that the DNI-GLSI models are applicable. A fast and short-lived deformation sub stage(ID-Fast) in the initial deformation stage was observed, and ID-Fast was driven by concentrated rainfall.
基金This work was supported by the National Key R&D Program of China[grant numbers 2016YFA0600403 and 2016YFA0602501]the General Project of the National Natural Science Foundation of China[grant number 41875134].
文摘In the paper,daily near-surface wind speed data from 462 stations are used to study the spatiotemporal characteristics of the annual and seasonal mean wind speed(MWS)and effective wind energy density(EWED)from 1960 to 2016,through the methods of kriging interpolation,leastsquares,correlation coefficient testing,and empirical orthogonal function(EOF)analysis.The results show that the annual MWS is larger than 3 m s-1 and the EWED is larger than 75 W m-2 in northern China and parts of coastal areas.However,the MWS and EWED values in southern China are all smaller than in northern China.Over the past 50 years,the annual and seasonal MWS in China has shown a significant decreasing trend,with the largest rate of decline in spring for northern China and winter for coastal areas.The annual MWS in some areas of Guangdong has an increasing trend,but it shows little change in southwestern China,South China,and west of Central China.Where the MWS is high,the rate of decline is also high.The main spatial distributions of the annual MWS and the annual EWED show high consistency,with a decreasing trend year by year.The decreasing trend of wind speed and wind energy resources in China is mainly related to global warming and land use/cover change.
基金Project supported by the State Key Development Program for Basic Research of China(Grant Nos.2013CB430204 and 2012CB955902)the National Natural Science Foundation of China(Grant Nos.41175067,41175084,and 41205040)
文摘In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and watervapor flux divergence in different seasons over northeast China and the water balance of that area. The data used in this paper is provided by the European Center for Medium-Range Weather Forecasts （ECMWF）. The results show that the spatial distributions of precipitable water, precipitation, and evaporation feature that the values of elements above in the southeastern area are larger than those in the northwestern area; in summer, much precipitation and evaporation occur in the Changbai Mountain region as a strong moisture convergence region; in spring and autumn, moisture divergence dominates the northeast of China; in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons changed in a truly imperceptible way. In spring, the evaporation exceeded the precipitation in northeast China; in summer, the precipitation was more prominent; in autumn and winter, precipitation played a more dominating role than the evaporation in the northern part of northeast China, while the evaporation exceeded the precipitation in the southern part. The Interim ECMWF Re-Analysis （ERA-Interim） data have properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA- Interim data can be used in the research of water balance in northeast China. On a seasonal scale, the moisture convergence has a greater influence than the local moisture variation on a moisture sink, and the latter is variable slightly, generally as a constant. Likewise, in different seasons, the total precipitation has a much greater influence than the evaporation on the moisture sink.
基金National Natural Science Foundation of China,No.41801052,No.41861013National Basic Work Program of MST,No.2013FY111400。
文摘Glaciers provide essential resources and services for human well-being and socio-economic development in arid regions.It is of great significance for regional socioeconomic sustainable development and environmental protection to conduct a glacier service value assessment and to analyze its spatiotemporal characteristics.Based on the first and second Chinese glacier inventories of the Qilian Mountains,a glacier service value evaluation system was established.Then the glacier service value and its spatiotemporal variation were assessed by combining the methods of unit area service price,value equivalent factor,and the glacier service value change index(GSCI).Three key results were obtained.(1)The total service value of glaciers in the Qilian Mountains for 2016 was 24.354 billion yuan.The main services provided were climate regulation and runoff regulation,which accounted for 60.58%and 33.14%of the total service value,respectively.Minor services were freshwater supply and hydropower,which accounted for 3.47%and 1.75%of the total value,respectively.The value of other types of services was about 0.259 billion yuan.(2)Among the various river systems in the Qilian Mountains,the Shule River basin had the highest glacier service value(7.771 billion yuan,31.91%),followed by the Haltang River basin(4.321 billion yuan,17.74%)and the Beida River basin(3.281 billion yuan,13.47%).In terms of administrative divisions,the glacier service value of the Qilian Mountains in Qinghai Province was 1.138 billion yuan higher than that of Gansu Province at 11.608 billion yuan,of which the services in the Haixi Mongol and Tibetan Autonomous Prefecture and Jiuquan City were valued at 11.124(45.68%)and 7.758(31.86%)billion yuan,respectively.(3)During the period from 1956 to 2010,the service value of glaciers in the Qilian Mountains declined by 435 million yuan,with an acceleration in the decreasing trend from west to east.
基金The Joint Advanced Marine and Ecological Studies(JAMES)in the Bay of Bengal and eastern equatorial Indian Ocean supported by the Global Change and Air-Sea InteractionⅡProgram under contract Nos GASI-01-EIND-STwin and GASI-04-WLHY-03Zhejiang Provincial Ten Thousand Talents Plan under contract No.2020R52038.
文摘A high-resolution customized numerical model is used to analyze the water transport in the three major water passages between the Andaman Sea(AS)and the Bay of Bengal,i.e.,the Preparis Channel(PC),the Ten Degree Channel(TDC),and the Great Channel(GC),based on the daily averaged simulation results ranging from 2010 to 2019.Spectral analysis and Empirical Orthogonal Function(EOF)methods are employed to investigate the spatiotemporal variability of the water exchange and controlling mechanisms.The results of model simulation indicate that the net average transports of the PC and GC,as well as their linear trend,are opposite to that of the TDC.This indicates that the PC and the GC are the main inflow channels of the AS,while the TDC is the main outflow channel of the AS.The transport variability is most pronounced at surface levels and between 100 m and 200 m depth,likely affected by monsoons and circulation.A 182.4-d semiannual variability is consistently seen in all three channels,which is also evident in their second principal components.Based on sea level anomalies and EOF analysis results,this is primarily due to equatorial winds during the monsoon transition period,causing eastward movement of Kelvin waves along the AS coast,thereby affecting the spatiotemporal characteristics of the flow in the AS.The first EOF of the PC flow field section shows a split at 100 m deep,likely due to topography.The first EOF of the TDC flow field section is steady but has potent seasonal oscillations in its time series.Meanwhile,the first EOF of the GC flow field section indicates a stable surface inflow,probably influenced by the equatorial Indian Ocean’s eastward current.
基金the Natural National Science Foundation of China,Grant/Award Number:31970993the major educational science planning project of Guangzhou,Grant/Award Number:2020zd003+1 种基金the Philosophy and Social Sciences Co-construction Project in Guangdong Province of China,Grant/Award Number:GD17XXL03the Youth Project of Humanities and Social Sciences by Ministry of Education in China,Grant/Award Number:19YJC190017。
文摘N170 is a negative event-related potential(ERP)component in response to visual stimuli,such as faces.It remains controversial whether N170 reflects the specific processing of faces or can also be elicited by objects of expertise(e.g.,words).In this research,we conducted a meta-analysis for the spatiotemporal characteristics of N170 of face and word stimuli from 24 studies in which both stimuli were presented for each subject.We observed that(1)both face and word stimuli can elicit conspicuous N170s and that there was no difference between the amplitude of face-N170 and word-N170;(2)there is no difference in the latencies between the two N170s;and(3)both N170s are distributed in the occipitotemporal regions but with a reversed hemispheric distribution pattern-faceN170 is more negative in the right than left occipitotemporal regions,while word-N170 is the opposite.These results showed that the face-and word-N170s are qualitatively the same but have different hemispheric lateralization advantages-N170 might be a general neural index of the expertise-dependent object-recognition process in occipitotemporal regions.
基金supported by the National Key R&D Program of China(2020YFA0714500,2019YFF01014401)The National Natural Science Foundation of China(12388102)+2 种基金Strategic Priority Research Program of Chinese Academy of Sciences(XDB0890102)Shanghai Science and Technology Committee Program(22DZ1100300,22560780100,23560750200)The Youth Innovation Promotion Association of the Chinese Academy of Sciences.
文摘The size of compression gratings has become a crucial factor in achieving 100-PW level super-intense ultrafast lasers,in view of the laser-induced damage of grating compressor.To improve the output laser energy within the damage threshold of grating compressor and therefore obtain higher laser peak power,we proposed the full-aperture grating compressor(FAGC).In this work,the spatiotemporal characteristics of the output pulses from FAGC are investigated,based on the SULF-10 PW laser facility with~400-mm beam diameter.The simulation and proof-of-principle experiment show that the pulse duration and the focusing quality of the output pulses from an FAGC are basically identical with those from a conventional 4-grating compressor;meanwhile,no evident diffractions are induced by the spectral clipping of FAGC.Thus,there is no marked influence of FAGC on the spatiotemporal characteristics of output compressed pulses.This work further demonstrates the feasibility of FAGC efficiently,which should be a promising scheme for realizing single-channel 100-PW level super-intense ultrafast lasers.
基金supported by the Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJZD-K201800702)Natural Science Foundation of Chongqing in China(No.cstc2020jcyj-jqX0004)+2 种基金Late Project of National Social Science Foundation in China(No.20FJYB035)the Ministry of education of Humanities and Social Science project(No.20YJA790016)the Fundamental Research Funds for the Central Universities(No.2018CDYJSY0055).
文摘Understanding the coupling relationship between ecosystem services and poverty livelihoods is a prerequisite for poverty eradication and ecological protection in China.In this paper,we intended to quantify the coupling relationship between ecosystem services and poverty livelihoods in 717 poverty-stricken counties in China.First,we identified distinct levels of ecosystem services and poverty respectively in the poverty-stricken areas based on the ecosystem services subsystem index and poverty livelihoods subsystem index.Then,we calculated the coupling degree and coupling coordination degree between the ecosystem services and the poverty livelihoods in China^poverty-stricken counties from 2000 to 2015.Finally,we analyzed the temporal and spatial evolution of the coupling between ecosystem services and poverty livelihoods.The results indicate that the ecosystem services showed a trend of first decreasing and then increasing,while the poverty level showed an increased trend.In addition,the coupling relationship between ecosystem services and poverty livelihoods in poverty-stricken counties was also improved from 2000 to 2015.However,the coupling degree value or coupling coordination degree values in some counties or contiguous impoverished areas showed a decreased trend,the coupling relationship between ecosystem services and poverty livelihoods in those counties or areas was higher conflict.Future more,the coupling relationship in China's poverty-stricken counties was mainly intermediate conflict and low conflict,which need to improve in the future.Thus,it is suggested that effective measures are required to lift ecosystem services out of the poverty trap and into sustainable livelihoods.
基金the National Natural Foundation of China(41704027,41664002,41864002)the Guangxi Natural Science Foundation of China(2017GXNSFBA198139,2017GXNSFDA198016,2018GXNSFAA281182,2018GXNSFAA281279)the“Ba Gui Scholars”program of the provincial government of Guangxi,and the Open Fund of Hunan Natural Resources Investigation and Monitoring Engineering Technology Research Center(No:2020-9).
文摘Precipitable Water Vapor(PWV),as an important indicator of atmospheric water vapor,can be derived from Global Navigation Satellite System(GNSS)observations with the advantages of high precision and all-weather capacity.GNSS-derived PWV with a high spatiotemporal resolution has become an important source of observations in mete-orology,particularly for severe weather conditions,for water vapor is not well sampled in the current meteorological observing systems.In this study,an empirical atmospheric weighted mean temperature(Tm)model for Guilin is estab-lished using the radiosonde data from 2012 to 2017.Then,the observations at 11 GNSS stations in Guilin are used to investigate the spatiotemporal features of GNSS-derived PWV under the heavy rainfalls from June to July 2017.The results show that the new Tm model in Guilin has better performance with the mean bias and Root Mean Square(RMS)of−0.51 and 2.12 K,respectively,compared with other widely used models.Moreover,the GNSS PWV estimates are validated with the data at Guilin radiosonde station.Good agreements are found between GNSS-derived PWV and radiosonde-derived PWV with the mean bias and RMS of−0.9 and 3.53 mm,respectively.Finally,an investigation on the spatiotemporal characteristics of GNSS PWV during heavy rainfalls in Guilin is performed.It is shown that variations of PWV retrieved from GNSS have a direct relationship with the in situ rainfall measurements,and the PWV increases sharply before the arrival of a heavy rainfall and decreases to a stable state after the cease of the rainfall.It also reveals the moisture variation in several regions of Guilin during a heavy rainfall,which is significant for the moni-toring of rainfalls and weather forecast.
基金The National Natural Science Foundation of China(No.51109039,5147814)
文摘The spatiotemporal characteristics of bridge deck runoff under a natural rainfall event are explored. The Taizhou Bridge is taken as a study case,and a hydrodynamic model based on the two-dimensional shallow water equations is used to analyze the runoff characteristics. The results indicate that the runoff velocity rate and depth are positively related to rainfall intensity,yet they have different response degrees to it. The inlet’s effect degree on lane water film has a positive relationship with rainfall intensity. A natural logarithm function( R^2= 0.706) can illustrate this relationship. However,the inlet’s effect degree on ponding at the curb shows a negative relationship with the rainfall intensity. A negative exponential function( R^2= 0.824) can reveal this relationship. With the decrease in the longitudinal slope SL,the ponding depth at the curb increases significantly at the bridge approach slab,whereas the lane water film thickness( WFT) is almost unchanged,but the lane WFT increases greatly at the location with the minimum longitudinal slope. It is concluded that the characteristics of the bridge deck runoff present apparent spatiotemporal differences,the inlet ’s effects on bridge deck runoff are quantitatively correlated with rainfall intensity, and the effective drainage measures are necessary for the bridge approach slab.
基金Young Taishan Scholars Program of Shandong Province,No.tsqn202103065National Natural Science Foundation of China,No.42371084。
文摘Tropical cyclone activity has undergone significant changes under the impact of global warming since the 20th century.However,the characteristic and trend changes of landfalling tropical cyclones over China still need to be further clarified.The study conducted an analysis of the spatiotemporal characteristics and trends of landfalling tropical cyclones over China from 1949 to 2022 using the dataset of the best tracks of tropical cyclones from the China Meteorological Administration.Additionally,we explored the influences of ENSO and the Pacific Decadal Oscillation(PDO)on landfalling tropical cyclone activities.The results indicate that:(1)The annual average number of landfalling tropical cyclones over China is approximately 8.85,showing a significant decreasing trend,and the decreasing range becomes larger with lower latitude overall.However,both the proportion of landfalling tropical cyclones to the total number and the percentage of higher intensity tropical cyclones increase.(2)The landfall locations of tropical cyclones in China are mainly concentrated between 18°N and 26°N,accounting for approximately 88.2%of the total,and the landfall frequency shows a sharp decline in the regions north of 30°N.The central landfall location of tropical cyclones has shifted significantly northwestward,moving closer to China.Compared to 1949–1969,the central genesis location from 2010 to 2022 shifted 4.5°westward and 2.0°northward.(3)There is a correlation between ENSO and the genesis frequency variation of tropical cyclones in the Northwest Pacific and landfalling over China.El Ni?o promotes the genesis of strong tropical cyclones and leads to a more southeastern bias in the genesis location of landfalling tropical cyclones,while La Ni?a has an opposite effect.The PDO also affects the tropical cyclones to a certain extent.During the PDO warm phase,the genesis position of tropical cyclones is westward and the number is smaller than that in the cold phase.This study further clarifies the changing trends and characteristics of landfalling tropical cyclones over China since 1949.It also highlights the impacts of ENSO and the PDO on tropical cyclone activities.The findings can serve as a scientific basis for conducting simulations and assessments of tropical cyclones and for disaster prevention and mitigation efforts.
基金supported by the National Natural Science Foundation of China(Grant No.52090082).
文摘A holistic and precise assessment of retaining wall deformations is critical for on-site risk management of large combined deep excavation projects,where the risk-related points are highly dispersed,evolving,and interacting.Despite extensive exploration of this topic in previous studies,the omission of intricate spatiotemporal characteristics of wall deformations has resulted in diminished prediction accuracy and stability.To mitigate this deficiency,a spatiotemporal characteristics matrix for all data points and time series was first generated for a deep excavation scenario and used as input for a new hybrid model that combines convolutional neural network(CNN)and long short-term memory(LSTM)with incorporated attention mechanism(CNN-LSTM-Att),which enables the cross-learning mechanism and improves interpretability.In addition,by leveraging the attention weight,a new risk assessment index for retaining wall deformations across various scenarios was formulated.Then the proposed method was applied in a large combined deep excavation in Shanghai,China.The results show that:(1)The incorporation of fedin characteristic data and the attention mechanism enables the proposed method to produce satisfactory prediction results for the holistic spatiotemporal distribution of a large combined excavation;(2)Compared with other published models,the proposed model shows much better prediction accuracy,interpretability,and stability,especially in medium-and long-term predictions;and(3)The new risk assessment index serves as a reliable decision-making tool for assessing the risk evolution of retaining wall deformations and provides valuable guidance for effective risk management in multi-scenario excavation projects.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFE0136000 and 2024YFC3013100)the Joint Meteorological Fund(Grant No.U2342211)+1 种基金the Joint Research Project for Meteorological Capacity Improvement(Grant No.22NLTSZ004)the National Meteorological Information Center(Grant No.NMICJY202301)。
文摘Using complex network methods,we construct undirected and directed heatwave networks to systematically analyze heatwave events over China from 1961 to 2023,exploring their spatiotemporal evolution patterns in different regions.The findings reveal a significant increase in heatwaves since the 2000s,with the average occurrence rising from approximately 3 to 5 times,and their duration increasing from 15 to around 30 days,nearly doubling.An increasing trend of“early onset and late withdrawal”of heatwaves has become more pronounced each year.In particular,eastern regions experience heatwaves that typically start earlier and tend to persist into September,exhibiting greater interannual variability compared to western areas.The middle and lower reaches of the Yangtze River and Xinjiang are identified as high-frequency heatwave areas.Complex network analysis reveals the dynamics of heatwave propagation,with degree centrality and synchronization distance indicating that the middle and lower reaches of the Yangtze River,Northeast China,and Xinjiang are key nodes in heatwave spread.Additionally,network divergence analysis shows that Xinjiang acts as a“source”area for heatwaves,exporting heat to surrounding regions,while the central region functions as a major“sink,”receiving more heatwave events.Further analysis from 1994 to 2023 indicates that heatwave events exhibit stronger network centrality and more complex synchronization patterns.These results suggest that complex networks provide a refined framework for depicting the spatiotemporal dynamics of heatwave propagation,offering new avenues for studying their occurrence and development patterns.
基金supported by the Special Fund for Meteorology-Scientific Research in the Public Interest,China(GYHY201106020)the National 973 Program of China(2010CB951502)
文摘The spatiotemporal characteristics of hydrothermal resources in southern rice production area of China have changed under the background of climate change,and this change would affect the effectiveness of hydrothermal resources during local rice growing period.According to the cropping system subdivision in southern rice production area of China during 1980s,this study used climate data from 254 meteorological stations and phonological data from 168 agricultural observation stations in the south of China,and adopted 6 international evaluation indices about the effectiveness of hydrothermal resources to analyze the temporal and spatial characteristics of hydrothermal resources during the growing period of single cropping rice system and double cropping rice system for 16 planting zones in the whole study area.The results showed that：in southern rice production area of China,the effectiveness of thermal resources of single cropping rice area（SCRA） was less than that of double cropping rice area（DCRA）,whereas the effectiveness of thermal resources of both SARA and DCRA showed a decreasing trend.The index value of effective precipitation satisfaction of SCRA was higher than that of DCRA,nevertheless the index value of effective precipitation satisfaction of both SCRA and DCRA showed a decreasing trend.There was a significant linear relationship between effective thermal resource and water demand,likely water demand increased by 18 mm with every 100°C d increase of effective heat.Effective precipitation satisfaction index（EPSI） showed a negative correlation with effective heat,yet showed a positive correlation with effective precipitation.EPSI reduced by 1% when effective heat resource increased by 125°C d.This study could provide insights for policy makers,land managers or farmers to improve water and heat resource uses and rationally arrange rice production activities under global climate change condition.
基金supported by the grants from National Natural Science Foundation of China(No.42077454)National Research Program for Key Issues in Air Pollution Control(DQGG202126)National Natural Science Foundation of China(No.41605077).
文摘Background:Biogenic volatile organic compounds(BVOCs)play an essential role in tropospheric atmospheric chemical reactions.There are few studies conducted on BVOCs emission of dominant forest species in the Jing-Jin-Ji area of China.Based on the field survey,forest resources data and the measured standard emission factors,the Guenther model developed in 1993(G93)was applied in this paper to estimate the emission of BVOCs from several dominant forest species(Platycladus orientalis,Quercus variabilis,Betula platyphylla,Populus tomentosa,Pinus tabuliformis,Robinia pseudoacacia,Ulmus pumila,Salix babylonica and Larix gmelinii)in the Jing-Jin-Ji area in 2017.Then the spatiotemporal emission characteristics and atmospheric chemical reactivity of these species were extensively evaluated.Results:The results showed that the total annual BVOCs emission was estimated to be 70.8 Gg C·year^(−1),consisting 40.5%(28.7 Gg C·year^(−1))of isoprene,36.0%(25.5 Gg C·year^(−1))of monoterpenes and 23.4%(16.6 Gg C·year^(−1))of other VOCs.The emissions from Platycladus orientalis,Quercus variabilis,Populus tomentosa and Pinus tabulaeformis contributed 56.1%,41.2%,36.0% and 31.1%,respectively.The total BVOCs emission from the Jing-Jin-Ji area accounted for 61.9% and 1.8%in summer and winter,respectively.Up to 28.8% of emission was detected from Chengde followed by Beijing with 24.9%,that mainly distributed in the Taihang Mountains and the Yanshan Mountains.Additionally,the Robinia pseudoacacia,Populus tomentosa,Quercus variabilis,and Pinus tabulaeformis contributed mainly to BVOCs reaction activity.Conclusions:The BVOCs emission peaked in summer(June,July,and August)and bottomed out in winter(December,January,and February).Chengde contributed the most,followed by Beijing.Platycladus orientalis,Quercus variabilis,Populus tomentosa,Pinus tabulaeformis and Robinia pseudoacacia represent the primary contributors to BVOCs emission and atmospheric reactivity,hence the planting of these species should be reduced.
基金supported by the National Natural Science Foundation of China(Grant Nos.51627811,51725702)the Science and Technology Project of State Grid Corporation of Beijing(Grant No.SGBJDK00DWJS2100164).
文摘Owing to the expansion of the grid interconnection scale,the spatiotemporal distribution characteristics of the frequency response of power systems after the occurrence of disturbances have become increasingly important.These characteristics can provide effective support in coordinated security control.However,traditional model-based frequencyprediction methods cannot satisfactorily meet the requirements of online applications owing to the long calculation time and accurate power-system models.Therefore,this study presents a rolling frequency-prediction model based on a graph convolutional network(GCN)and a long short-term memory(LSTM)spatiotemporal network and named as STGCN-LSTM.In the proposed method,the measurement data from phasor measurement units after the occurrence of disturbances are used to construct the spatiotemporal input.An improved GCN embedded with topology information is used to extract the spatial features,while the LSTM network is used to extract the temporal features.The spatiotemporal-network-regression model is further trained,and asynchronous-frequency-sequence prediction is realized by utilizing the rolling update of measurement information.The proposed spatiotemporal-network-based prediction model can achieve accurate frequency prediction by considering the spatiotemporal distribution characteristics of the frequency response.The noise immunity and robustness of the proposed method are verified on the IEEE 39-bus and IEEE 118-bus systems.
基金supported by the National Natural Science Foundation of China(Grant No.41971239)the Second Tibetan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0402)+1 种基金Lancang-Mekong Cooperation Project on China-Laos Cross-border Asian Elephant Habitat Quality Assessment(Grant No.102169221100000009022)the Graduate Research Innovation Project of Yunnan University(Grant No.2021Y368).
文摘Human-wildlife conflict(HWC)and its socioeconomic impacts are a pressing global issue.Accurately quantifying HWCs and their interaction with residential development is crucial for rural revitalization and biodiversity conservation efforts.This study investigates the interplay between rural residential expansion(RRE)with humanelephant conflict(HEC)in southern Yunnan Province using high-accuracy yearly land use/land cover data and Asian elephant accident data.A piecewise regression along with several metrics,including expansion intensity,rate of rural residential land,and residential density,were employed to analyze the spatial-temporal change characteristics of RRE.Then,a geographical detector and a bivariate spatial autocorrelation model were used to reveal the driving mechanisms of RRE,with particular emphasis on the spatial relations between RRE and HECs.The results indicate that HECs had a significant negative impact on RRE,exhibiting higher expansion intensity and rate of rural residential land in non-HEC areas than in HEC areas.High spatiotemporal consistency between accelerated RRE and intensified HECs occurred from 2010 onwards,which aligns with the year when the trend of settlement area expansion changed.RRE activities and ensuing land use conversions led to increased occurrences of HECs,which negatively affected the RRE.Compared to HECs,topography and locational factors exhibited a secondary effect on RRE activities.The findings underscore reciprocal feedback mechanisms between RRE and HECs and the elevated risk of adverse interactions between humans and elephants within the range of China’s wild elephants,providing theoretical support for coordinating conservation initiatives for Asian elephants with rural revitalization in the border areas of Southwest China.
