Sparse large-scale multi-objective optimization problems(SLMOPs)are common in science and engineering.However,the large-scale problem represents the high dimensionality of the decision space,requiring algorithms to tr...Sparse large-scale multi-objective optimization problems(SLMOPs)are common in science and engineering.However,the large-scale problem represents the high dimensionality of the decision space,requiring algorithms to traverse vast expanse with limited computational resources.Furthermore,in the context of sparse,most variables in Pareto optimal solutions are zero,making it difficult for algorithms to identify non-zero variables efficiently.This paper is dedicated to addressing the challenges posed by SLMOPs.To start,we introduce innovative objective functions customized to mine maximum and minimum candidate sets.This substantial enhancement dramatically improves the efficacy of frequent pattern mining.In this way,selecting candidate sets is no longer based on the quantity of nonzero variables they contain but on a higher proportion of nonzero variables within specific dimensions.Additionally,we unveil a novel approach to association rule mining,which delves into the intricate relationships between non-zero variables.This novel methodology aids in identifying sparse distributions that can potentially expedite reductions in the objective function value.We extensively tested our algorithm across eight benchmark problems and four real-world SLMOPs.The results demonstrate that our approach achieves competitive solutions across various challenges.展开更多
Accurate meteorological predictions in the Arctic are important in response to the rapid climate change and insufficient meteorological observations in the Arctic.In this study,we adopted a high-resolution Weather Res...Accurate meteorological predictions in the Arctic are important in response to the rapid climate change and insufficient meteorological observations in the Arctic.In this study,we adopted a high-resolution Weather Research and Forecasting(WRF)model to simulate the meteorology at two Arctic stations(Barrow and Summit)in April 2019.Simulation results were also evaluated by using surface measurements and statistical parameters.In addition,weather charts during the studied time period were also used to assess the model performance.The results demonstrate that the WRF model is able to accurately capture the meteorological parameters for the two Arctic stations and the weather systems such as cyclones and anticyclones in the Arctic.Moreover,we found the model performance in predicting the surface pressure the best while the performance in predicting the wind the worst among these meteorological predictions.However,the wind predictions at these Arctic stations were found to be more accurate than those at urban stations in mid-latitude regions,due to the differences in land features and anthropogentic heat sources between these regions.In addition,a comparison of the simulation results showed that the prediction of meteorological conditions at Summit is superior to that at Barrow.Possible reasons for the deviations in temperature predictions between these two Arctic stations are uncertainties in the treatments of the sea ice and the cloud in the model.With respect to the wind,the deviations may source from the overestimation of the wind over the sea and at coastal stations.展开更多
sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which ob...sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: ① The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; ② The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; ③ Before the main rupture of the rock sample the obvious ″tendency anomaly′ and ′short-term anomaly″ were observed, and some of them could be likely considered as the ″impending earthquake ″anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.展开更多
Knowledge of the statistical characteristics of inversions and their effects on aerosols under different large-scale synoptic circulations is important for studying and modeling the diffusion of pollutants in the boun...Knowledge of the statistical characteristics of inversions and their effects on aerosols under different large-scale synoptic circulations is important for studying and modeling the diffusion of pollutants in the boundary layer. Based on results gen- erated using the self-organizing map （SOM） weather classification method, this study compares the statistical characteristics of surface-based inversions （SBIs） and elevated inversions （EIs）, and quantitatively evaluates the effect of SBIs on aerosol condensation nuclei （CN） concentrations and the relationship between temperature gradients and aerosols for six prevailing synoptic patterns over the the Southern Great Plains （SGP） site during 2001-10. Large-scale synoptic patterns strongly influ- ence the statistical characteristics of inversions and the accumulation of aerosols in the low-level atmosphere. The activity, frequency, intensity, and vertical distribution of inversions are significantly different among these synoptic patterns. The verti- cal distribution of inversions varies diurnally and is significantly different among the different synoptic patterns. Anticyclonic patterns affect the accumulation of aerosols near the ground more strongly than cyclonic patterns. Mean aerosol CN con- centrations increase during SBIs compared to no inversion cases by 16.1%, 22.6%, 24.5%, 58.7%, 29.8% and 23.7% for the six synoptic patterns. This study confirms that there is a positive correlation between temperature gradients and aerosol CN concentrations near the ground at night under similar large-scale synoptic patterns. The relationship is different for different synoptic patterns and can be described by linear functions. These findings suggest that large-scale synoptic patterns change the static stability of the atmosphere and inversions in the lower atmosphere, thereby influencing the diffusion of aerosols near the ground.展开更多
Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998–2004 and its weather-influencing system,multiple synthesized physical fields in the middle–upper troposphere of the out- a...Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998–2004 and its weather-influencing system,multiple synthesized physical fields in the middle–upper troposphere of the out- and in-TPV are computationally analyzed by using re-analysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) of United States.Our research shows that the departure of TPV is caused by the mutual effects among the weather systems in Westerlies and in the subtropical area,within the middle and the upper troposphere.This paper describes the large-scale meteorological condition and the physics image of the departure of TPV,and the main differences among the large-scale conditions for all types of TPVs.This study could be used as the scientific basis for predicting the torrential rain and the floods caused by the TPV departure.展开更多
We analyzed the hydrographic variability of La Paz Bay, the largest coastal water body in the Gulf of California, and its relationship with Pacific large-scale phenomena, including the El Ni?o-Southern Oscillation (EN...We analyzed the hydrographic variability of La Paz Bay, the largest coastal water body in the Gulf of California, and its relationship with Pacific large-scale phenomena, including the El Ni?o-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Pacific-North America pattern (PNA), and North Pacific pattern (NP). We used several indices related to these phenomena and the hydrographic variability data of La Paz Bay, consisting of the annual sea surface temperature patterns from satellite imagery from 2000 to 2010 and the mixed layer depths measured with?in situ?data from 1994 to 2009. The results indicate the sea surface temperature fluctuated during the study period, with 2007 as the coldest year and 2009 as the warmest. Two periods were identified in the annual thermal cycle of the bay, one period of warmth from June to November, and one of cold from December to May. The sea surface temperature is primarily influenced by the ENSO. The mixed layer depth analysis showed its absence during August-September, while the deepest ones were in November-March. The unusual 100 m mixed layer depth noted during February 2002 and its absence in March 1996 and 2009 were related to uncommon atmospheric conditions in the annual patterns of the ENSO, PNA, and NP. The variability of the mixed layer depth is primarily related to the variability of the NP. We concluded that the hydrographic conditions of La Paz Bay are most influenced by the NP during the cold phase of its annual cycle, and by the ENSO during the warm phase.展开更多
[目的]揭示黄土高原典型区域百年尺度干旱演化特征,与地貌类型耦合阐明气象干旱的时空变化规律,进而为北洛河流域综合治理提供科技支撑。[方法]基于1915—2020年北洛河流域1 km分辨率的平均气温及降水数据,计算了年际标准化降水蒸散指数...[目的]揭示黄土高原典型区域百年尺度干旱演化特征,与地貌类型耦合阐明气象干旱的时空变化规律,进而为北洛河流域综合治理提供科技支撑。[方法]基于1915—2020年北洛河流域1 km分辨率的平均气温及降水数据,计算了年际标准化降水蒸散指数(SPEI),并结合Theil-Sen Median趋势分析、Mann-Kendall检验、小波分析、反距离权重插值(IDW)等方法,分析了流域内100余年不同地貌类型区的气象干旱时空演变特征。[结果](1)北洛河流域降水量及平均气温的空间分布差异较大,总体呈现东南向西北递减的特点;降水量多呈条带状分布,平均气温沿河道自上而下梯度增加,上游区(丘陵沟壑区)降水量相对较少,下游区(阶地平原区)平均气温相对偏高;(2) 1915—2020年北洛河流域SPEI-12震荡明显,干旱事件交替出现且弱减,下降速率为-0.04/10 a, 1942年,1990年和2010年为旱势转折年,并以1990年最为明显;周期变化大致可从1960年分为两个时期,之前以10 a, 17 a为主,其后为3 a, 7 a, 30 a左右,10 a和30 a周期在不同时期干旱变化中起主导作用;(3) SPEI-12的不显著下降趋势具有全域性且由东北向西南有增大趋势,表明北洛河流域总体呈弱旱化发展;(4)不同年代干旱事件发生频率差异较大,1990s重旱和特旱发生频率最高;2000s不同类型干旱事件发生的总频率最大,其中上游区(丘陵沟壑区)和下游区(阶地平原区)可达70%,而中游区(土石山林区和高原沟壑区)约为60%;(5)不同类型干旱空间分布存在异质性,轻旱发生频率有自南向北逐渐降低的趋势,中旱发生频率与之相反。总体来看,北洛河流域上游区(丘陵沟壑区)易发生中旱,下游区(阶地平原区)更易发生轻旱,重旱高发区在流域内零散分布,特旱的发生概率仅为1.69%~2.10%。[结论]全球变暖引发的旱化趋势在黄土高原地区的影响客观存在,北洛河流域不同地貌类型区气象干旱发生的高频类型略有差别,未来应提升中下游地区的抗旱减灾能力。展开更多
An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017.73 out of 96 selected cities,most located in the Beijing-TianjinHebei and the surrounding area(BTHS),s...An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017.73 out of 96 selected cities,most located in the Beijing-TianjinHebei and the surrounding area(BTHS),suffered severe ozone pollution.A north-south contrast ozone distribution,with higher ozone(199±33μg/m3)in the BTHS and lower ozone(118±25μg/m^3)in the Yangtze River Delta(YRD),was found to be dominated by the position of the West Pacific Subtropical High(WPSH)and mid-high latitude wave activities.In the BTHS,the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation.Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity(RH),less total cloud cover(TGC),strong solar radiation and high temperatures.Moreover,southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O3 and its precursors.On one hand,the deep sinking motion and inversion layer suppressed the dispersion of pollutants.On the other hand,O3-rich air in the upper layer was maintained at night due to temperature inversion,which facilitated O3 vertical transport to the surface in the next-day morning due to elevated convection.Generally,temperature,UV radiation,and RH showed good correlations with O3 in the BTHS,with rates of 8.51(μg/m^3)/℃(within the temperature range of 20-38℃),59.54(μg/m^3)/(MJ/m^2)and-1.93(μg/m^3)/%,respectively.展开更多
This paper intends to investigate the urban spatial patterns of Hubei Province and its evolution from three different perspectives: urban nodes, urban connections and urban clusters. The research adopts nighttime ligh...This paper intends to investigate the urban spatial patterns of Hubei Province and its evolution from three different perspectives: urban nodes, urban connections and urban clusters. The research adopts nighttime light imagery of cities in Hubei Province, the viewpoint of ′point-axis-area′ in the ′point-axis system′ theory, and employs light index model, gravity model and social network analysis. The findings are as follows: 1) In terms of urban nodes, the urbanization process of Hubei has been carried out mainly on the basis of external expansion rather than internal increasing. The polarization trend of urban connection network is strengthening. 2) As for urban connections, the estimation of urban connections using light index model is capable of containing various actual flow, and the connections are getting increasingly closer. 3) In regard to urban groups, seven urban groups of varying sizes have formed. On that basis, three stable and relatively independent urban groups as the centers, namely Wuchang, Yichang and Xiangyang emerge as well. But the structures of ′Wuhan Metropolitan Area′, ′Yichang-Jingzhou-Jingmen City Group′ and ′Xiangyang-Shiyen-Suizhou City Group′, which are defined by local development strategy in Hubei Province, are different from the above three urban groups.展开更多
A statistical analysis of the initial vortexes leading to tropical cyclone(TC)formation in the western North Pacific(WNP)is conducted with the ECMWF ERA5 reanalysis data from 1999 to 2018.It is found that TCs in the W...A statistical analysis of the initial vortexes leading to tropical cyclone(TC)formation in the western North Pacific(WNP)is conducted with the ECMWF ERA5 reanalysis data from 1999 to 2018.It is found that TCs in the WNP basically originate from three kinds of vortexes,i.e.,a mid-level vortex(MV),a low-level vortex(LV),and a relatively deep vortex with notable vorticity in both the lower and middle troposphere(DV).Among them,LV and DV account for 47.9%and 24.2%of tropical cyclogenesis events,respectively,while only 27.9%of TCs develop from the MV,which is much lower than that which occurs in the North Atlantic and eastern Pacific.Such a difference might be ascribed to the active monsoon systems in the WNP all year round.Due to the nearly upright structure of mid-level convergence in the early pre-genesis stage,TC genesis efficiency is the highest in DV.Compared with MV,LV generally takes a shorter time to intensify to a TC because of the higher humidity and the stronger low-level cyclonic circulation,which is related to air-sea interaction and boundary-layer convergence.Further examination of the relationship between tropical cyclogenesis and large-scale flow patterns indicate that the TC genesis events associated with LV are primarily related to the monsoon shear line,monsoon confluence region,and monsoon gyre,while those associated with MV are frequently connected with easterly waves and wave energy dispersion of preexisting TC.Compared with other flow patterns,tropical cyclones usually form and intensify faster in the monsoon confluence region.展开更多
The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and...The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and complexity.Recently,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods.However,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics.To this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state.After matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion.The applicability and effectiveness of the proposed approach are examined in a road network of Beijing,China.Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.展开更多
This study uses methods,such as a nearest proximity index,nuclear density,spatial interpolation,buffering zone,and overlay analysis,based on an exploratory spatial data analysis tool.It focuses on a large commercial f...This study uses methods,such as a nearest proximity index,nuclear density,spatial interpolation,buffering zone,and overlay analysis,based on an exploratory spatial data analysis tool.It focuses on a large commercial facility in which a mathematical analysis is conducted on its spatial patterns.In the study,45 large-scale retail commercial facilities(LSRCFs)in the Gulou District,Nanjing,China,were chosen,and the spatial concentration,density,and structure of the LSRCFs in this area were analyzed.Three additional factors,namely,population,transportation,and consumption,were examined to determine their impact on the spatial patterns of the LSRCFs.Finally,this study recommends a spatial layout for the future of the Gulou District according to the analysis results.展开更多
基金support by the Open Project of Xiangjiang Laboratory(22XJ02003)the University Fundamental Research Fund(23-ZZCX-JDZ-28,ZK21-07)+5 种基金the National Science Fund for Outstanding Young Scholars(62122093)the National Natural Science Foundation of China(72071205)the Hunan Graduate Research Innovation Project(CX20230074)the Hunan Natural Science Foundation Regional Joint Project(2023JJ50490)the Science and Technology Project for Young and Middle-aged Talents of Hunan(2023TJZ03)the Science and Technology Innovation Program of Humnan Province(2023RC1002).
文摘Sparse large-scale multi-objective optimization problems(SLMOPs)are common in science and engineering.However,the large-scale problem represents the high dimensionality of the decision space,requiring algorithms to traverse vast expanse with limited computational resources.Furthermore,in the context of sparse,most variables in Pareto optimal solutions are zero,making it difficult for algorithms to identify non-zero variables efficiently.This paper is dedicated to addressing the challenges posed by SLMOPs.To start,we introduce innovative objective functions customized to mine maximum and minimum candidate sets.This substantial enhancement dramatically improves the efficacy of frequent pattern mining.In this way,selecting candidate sets is no longer based on the quantity of nonzero variables they contain but on a higher proportion of nonzero variables within specific dimensions.Additionally,we unveil a novel approach to association rule mining,which delves into the intricate relationships between non-zero variables.This novel methodology aids in identifying sparse distributions that can potentially expedite reductions in the objective function value.We extensively tested our algorithm across eight benchmark problems and four real-world SLMOPs.The results demonstrate that our approach achieves competitive solutions across various challenges.
基金funded by the National Key Research and Development Program of China(Grant no.2022YFC3701204)the 2023 Outstanding Young Backbone Teacher of Jiangsu“Qinglan”Project(Grant no.R2023Q02)the National Natural Science Foundation of China(Grant no.41705103).
文摘Accurate meteorological predictions in the Arctic are important in response to the rapid climate change and insufficient meteorological observations in the Arctic.In this study,we adopted a high-resolution Weather Research and Forecasting(WRF)model to simulate the meteorology at two Arctic stations(Barrow and Summit)in April 2019.Simulation results were also evaluated by using surface measurements and statistical parameters.In addition,weather charts during the studied time period were also used to assess the model performance.The results demonstrate that the WRF model is able to accurately capture the meteorological parameters for the two Arctic stations and the weather systems such as cyclones and anticyclones in the Arctic.Moreover,we found the model performance in predicting the surface pressure the best while the performance in predicting the wind the worst among these meteorological predictions.However,the wind predictions at these Arctic stations were found to be more accurate than those at urban stations in mid-latitude regions,due to the differences in land features and anthropogentic heat sources between these regions.In addition,a comparison of the simulation results showed that the prediction of meteorological conditions at Summit is superior to that at Barrow.Possible reasons for the deviations in temperature predictions between these two Arctic stations are uncertainties in the treatments of the sea ice and the cloud in the model.With respect to the wind,the deviations may source from the overestimation of the wind over the sea and at coastal stations.
文摘sing the natural limestone samples taken from the field with dimension of 500 mm×500 mm×1 000 mm, the D-D (dilatancy-diffusion) seismogeny pattern was modeled under the condition of water injection, which observes the time-space evolutionary features about the relative physics fields of the loaded samples from deformation, formation of microcracks to the occurrence of main rupture. The results of observed apparent resistivity show: ① The process of the deformation from microcrack to main rupture on the loaded rock sample could be characterized by the precursory spatial-temporal changes in the observation of apparent resistivity; ② The precursory temporal changes of observation in apparent resistivity could be divided into several stages, and its spatial distribution shows the difference in different parts of the rock sample; ③ Before the main rupture of the rock sample the obvious ″tendency anomaly′ and ′short-term anomaly″ were observed, and some of them could be likely considered as the ″impending earthquake ″anomaly precursor of apparent resistivity. The changes and distribution features of apparent resistivity show that they are intrinsically related to the dilatancy phenomenon of the loaded rock sample. Finally, this paper discusses the mechanism of resistivity change of loaded rock sample theoretically.
基金sponsored by the U.S. Department of Energy (DOE)supported by the Ministry of Science and Technology of China (Grant Nos. 2010CB950804 and 2013CB955801)+1 种基金the "Strategic Priority Research Program" of the Chinese Academy of Sciences (Grant No. XDA05100300)the National Natural Science Foundation of China (Grant No. 41305011)
文摘Knowledge of the statistical characteristics of inversions and their effects on aerosols under different large-scale synoptic circulations is important for studying and modeling the diffusion of pollutants in the boundary layer. Based on results gen- erated using the self-organizing map （SOM） weather classification method, this study compares the statistical characteristics of surface-based inversions （SBIs） and elevated inversions （EIs）, and quantitatively evaluates the effect of SBIs on aerosol condensation nuclei （CN） concentrations and the relationship between temperature gradients and aerosols for six prevailing synoptic patterns over the the Southern Great Plains （SGP） site during 2001-10. Large-scale synoptic patterns strongly influ- ence the statistical characteristics of inversions and the accumulation of aerosols in the low-level atmosphere. The activity, frequency, intensity, and vertical distribution of inversions are significantly different among these synoptic patterns. The verti- cal distribution of inversions varies diurnally and is significantly different among the different synoptic patterns. Anticyclonic patterns affect the accumulation of aerosols near the ground more strongly than cyclonic patterns. Mean aerosol CN con- centrations increase during SBIs compared to no inversion cases by 16.1%, 22.6%, 24.5%, 58.7%, 29.8% and 23.7% for the six synoptic patterns. This study confirms that there is a positive correlation between temperature gradients and aerosol CN concentrations near the ground at night under similar large-scale synoptic patterns. The relationship is different for different synoptic patterns and can be described by linear functions. These findings suggest that large-scale synoptic patterns change the static stability of the atmosphere and inversions in the lower atmosphere, thereby influencing the diffusion of aerosols near the ground.
基金Supported by the Natural Science Foundation of China,No40475020Special Project of National Sci./Tech. Basic Research No 2006FY220300
文摘Based on the circumfluence situation of the out- and in-Tibet Plateau Vortex (TPV) from 1998–2004 and its weather-influencing system,multiple synthesized physical fields in the middle–upper troposphere of the out- and in-TPV are computationally analyzed by using re-analysis data from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) of United States.Our research shows that the departure of TPV is caused by the mutual effects among the weather systems in Westerlies and in the subtropical area,within the middle and the upper troposphere.This paper describes the large-scale meteorological condition and the physics image of the departure of TPV,and the main differences among the large-scale conditions for all types of TPVs.This study could be used as the scientific basis for predicting the torrential rain and the floods caused by the TPV departure.
文摘We analyzed the hydrographic variability of La Paz Bay, the largest coastal water body in the Gulf of California, and its relationship with Pacific large-scale phenomena, including the El Ni?o-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Pacific-North America pattern (PNA), and North Pacific pattern (NP). We used several indices related to these phenomena and the hydrographic variability data of La Paz Bay, consisting of the annual sea surface temperature patterns from satellite imagery from 2000 to 2010 and the mixed layer depths measured with?in situ?data from 1994 to 2009. The results indicate the sea surface temperature fluctuated during the study period, with 2007 as the coldest year and 2009 as the warmest. Two periods were identified in the annual thermal cycle of the bay, one period of warmth from June to November, and one of cold from December to May. The sea surface temperature is primarily influenced by the ENSO. The mixed layer depth analysis showed its absence during August-September, while the deepest ones were in November-March. The unusual 100 m mixed layer depth noted during February 2002 and its absence in March 1996 and 2009 were related to uncommon atmospheric conditions in the annual patterns of the ENSO, PNA, and NP. The variability of the mixed layer depth is primarily related to the variability of the NP. We concluded that the hydrographic conditions of La Paz Bay are most influenced by the NP during the cold phase of its annual cycle, and by the ENSO during the warm phase.
文摘[目的]揭示黄土高原典型区域百年尺度干旱演化特征,与地貌类型耦合阐明气象干旱的时空变化规律,进而为北洛河流域综合治理提供科技支撑。[方法]基于1915—2020年北洛河流域1 km分辨率的平均气温及降水数据,计算了年际标准化降水蒸散指数(SPEI),并结合Theil-Sen Median趋势分析、Mann-Kendall检验、小波分析、反距离权重插值(IDW)等方法,分析了流域内100余年不同地貌类型区的气象干旱时空演变特征。[结果](1)北洛河流域降水量及平均气温的空间分布差异较大,总体呈现东南向西北递减的特点;降水量多呈条带状分布,平均气温沿河道自上而下梯度增加,上游区(丘陵沟壑区)降水量相对较少,下游区(阶地平原区)平均气温相对偏高;(2) 1915—2020年北洛河流域SPEI-12震荡明显,干旱事件交替出现且弱减,下降速率为-0.04/10 a, 1942年,1990年和2010年为旱势转折年,并以1990年最为明显;周期变化大致可从1960年分为两个时期,之前以10 a, 17 a为主,其后为3 a, 7 a, 30 a左右,10 a和30 a周期在不同时期干旱变化中起主导作用;(3) SPEI-12的不显著下降趋势具有全域性且由东北向西南有增大趋势,表明北洛河流域总体呈弱旱化发展;(4)不同年代干旱事件发生频率差异较大,1990s重旱和特旱发生频率最高;2000s不同类型干旱事件发生的总频率最大,其中上游区(丘陵沟壑区)和下游区(阶地平原区)可达70%,而中游区(土石山林区和高原沟壑区)约为60%;(5)不同类型干旱空间分布存在异质性,轻旱发生频率有自南向北逐渐降低的趋势,中旱发生频率与之相反。总体来看,北洛河流域上游区(丘陵沟壑区)易发生中旱,下游区(阶地平原区)更易发生轻旱,重旱高发区在流域内零散分布,特旱的发生概率仅为1.69%~2.10%。[结论]全球变暖引发的旱化趋势在黄土高原地区的影响客观存在,北洛河流域不同地貌类型区气象干旱发生的高频类型略有差别,未来应提升中下游地区的抗旱减灾能力。
基金supported by a grant from the National Key R&D Plan(Quantitative Relationship and Regulation Principle between Regional Oxidation Capacity of Atmospheric and Air Quality 2017YFC0210003)the National Natural Science Foundation of China(No.41505133&41775162)+1 种基金the National Research Program for Key Issues in Air Pollution Control(DQGG0101)the Beijing Major Science and Technology Project 510(No.Z181100005418014)。
文摘An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017.73 out of 96 selected cities,most located in the Beijing-TianjinHebei and the surrounding area(BTHS),suffered severe ozone pollution.A north-south contrast ozone distribution,with higher ozone(199±33μg/m3)in the BTHS and lower ozone(118±25μg/m^3)in the Yangtze River Delta(YRD),was found to be dominated by the position of the West Pacific Subtropical High(WPSH)and mid-high latitude wave activities.In the BTHS,the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation.Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity(RH),less total cloud cover(TGC),strong solar radiation and high temperatures.Moreover,southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O3 and its precursors.On one hand,the deep sinking motion and inversion layer suppressed the dispersion of pollutants.On the other hand,O3-rich air in the upper layer was maintained at night due to temperature inversion,which facilitated O3 vertical transport to the surface in the next-day morning due to elevated convection.Generally,temperature,UV radiation,and RH showed good correlations with O3 in the BTHS,with rates of 8.51(μg/m^3)/℃(within the temperature range of 20-38℃),59.54(μg/m^3)/(MJ/m^2)and-1.93(μg/m^3)/%,respectively.
基金Under the auspices of National Natural Science Foundation of China(No.41001100,41371183)Humanities and Social Sciences Foundation of Ministry of Education in China(No.15YJCZH174)+1 种基金Humanities Sciences Foundation of Ministry of Hubei Province(No.15YJCZH174)Fundamental Research Funds for the Central Universities(No.CCNU15A06069,CCNU15ZD001)
文摘This paper intends to investigate the urban spatial patterns of Hubei Province and its evolution from three different perspectives: urban nodes, urban connections and urban clusters. The research adopts nighttime light imagery of cities in Hubei Province, the viewpoint of ′point-axis-area′ in the ′point-axis system′ theory, and employs light index model, gravity model and social network analysis. The findings are as follows: 1) In terms of urban nodes, the urbanization process of Hubei has been carried out mainly on the basis of external expansion rather than internal increasing. The polarization trend of urban connection network is strengthening. 2) As for urban connections, the estimation of urban connections using light index model is capable of containing various actual flow, and the connections are getting increasingly closer. 3) In regard to urban groups, seven urban groups of varying sizes have formed. On that basis, three stable and relatively independent urban groups as the centers, namely Wuchang, Yichang and Xiangyang emerge as well. But the structures of ′Wuhan Metropolitan Area′, ′Yichang-Jingzhou-Jingmen City Group′ and ′Xiangyang-Shiyen-Suizhou City Group′, which are defined by local development strategy in Hubei Province, are different from the above three urban groups.
基金supported in part by the Nature Science Foundation of China under Grant Nos.41875046,42175004National Key Research and Development Program of China under Grant No.2017YFC1501601Shanghai“Science and Technology Innovation Action Plan”Yangtze River Delta Science and Technology Innovation Community Field Project Grant 21002410200。
文摘A statistical analysis of the initial vortexes leading to tropical cyclone(TC)formation in the western North Pacific(WNP)is conducted with the ECMWF ERA5 reanalysis data from 1999 to 2018.It is found that TCs in the WNP basically originate from three kinds of vortexes,i.e.,a mid-level vortex(MV),a low-level vortex(LV),and a relatively deep vortex with notable vorticity in both the lower and middle troposphere(DV).Among them,LV and DV account for 47.9%and 24.2%of tropical cyclogenesis events,respectively,while only 27.9%of TCs develop from the MV,which is much lower than that which occurs in the North Atlantic and eastern Pacific.Such a difference might be ascribed to the active monsoon systems in the WNP all year round.Due to the nearly upright structure of mid-level convergence in the early pre-genesis stage,TC genesis efficiency is the highest in DV.Compared with MV,LV generally takes a shorter time to intensify to a TC because of the higher humidity and the stronger low-level cyclonic circulation,which is related to air-sea interaction and boundary-layer convergence.Further examination of the relationship between tropical cyclogenesis and large-scale flow patterns indicate that the TC genesis events associated with LV are primarily related to the monsoon shear line,monsoon confluence region,and monsoon gyre,while those associated with MV are frequently connected with easterly waves and wave energy dispersion of preexisting TC.Compared with other flow patterns,tropical cyclones usually form and intensify faster in the monsoon confluence region.
基金the National Natural Science Foundation of China(U1564212,61773036,51508014)Beijing Natural Science Foundation(9172011)Young Elite Scientist Sponsorship Program of the China Association for Science and Technology(2016QNRC001)。
文摘The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and complexity.Recently,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods.However,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics.To this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state.After matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion.The applicability and effectiveness of the proposed approach are examined in a road network of Beijing,China.Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.
文摘This study uses methods,such as a nearest proximity index,nuclear density,spatial interpolation,buffering zone,and overlay analysis,based on an exploratory spatial data analysis tool.It focuses on a large commercial facility in which a mathematical analysis is conducted on its spatial patterns.In the study,45 large-scale retail commercial facilities(LSRCFs)in the Gulou District,Nanjing,China,were chosen,and the spatial concentration,density,and structure of the LSRCFs in this area were analyzed.Three additional factors,namely,population,transportation,and consumption,were examined to determine their impact on the spatial patterns of the LSRCFs.Finally,this study recommends a spatial layout for the future of the Gulou District according to the analysis results.
