With the rapid parallel development of high-speed rail and air transportation, the HSR-air competitive network has undergone great changes. Using the data of city pairs with both air and HSR service in the period of 2007-2015, this article explores the evolution of spatio-temporal pattern of HSR-Air competitive network at the national scale, and then reveals its expansion mode as well as the main driving factors. The results are as following: 1) The HSR-air competitive network grows rapidly in size. Spatially, while a tendency of expanding westward and southward is manifested, the overlapping market of 2 transportation modes still focuses on the eastern coastal region. 2) The city-pairs with potential HSR-Air competition are inclined to link the top city nodes, and the HSR-air competitive network presents a hierarchical structure with Beijing and Shanghai as centers. 3) The overlapping market of HSR and air transportation expands from city-pairs with medium distance to long distance. HSR dominates city-pairs with distance below 700 km and has relative advantage in the range of 700 to 1 000 km compared to air transportation. While air transportation dominates city-pairs with distance over 1 500 km. The competition between HSR and air transportation intensifies in the range of 1 000-1 500 km. 4) The HSR-air competitive network has shown a “core-core” pattern in the early period and then grows to a “core-periphery” pattern later. City size, urban function as well as geographical proximity are main factors for shaping the HSR-air overlapping network.
Based on the research on population spatial diffusion and its variation in migration, this study proposes that a new path of urbanization in central area of China is emerging, namely returning-migrant-induced urbanization (RMIU). Through conducting an intensive questionnaire survey and a lot of interviews in several cities in Middle China, as well as comparing with urbanization pathways in the coastal China, we conclude 3 new characteristics of the RMIU. First, the county-level central cities have become the main attractive places for hosting returning migrants, where is the first choice for a large share of returning migrants. This is due to abundant job opportunities, good public service, better education resources, good living condition and lower living expenses. Unlike their elder generation returning from coastal areas who become peasants again, the new returning generation is still working in non-agricultural fields, both in manufacturing industries and tertiary sector. Second, many “pendular populations” are existing in counties and county-level cities, which means people working in cities, but living in countryside. Therefore, this is a centripetal urbanization featured as the strong county proper, which is much different from urbanization process in coastal China, such as exo-urbanization, urbanization from below, peri-urbanization, in situ urbanization. Third, the prefectural cities are also an important option for returning migrants for living and working, especially for those people with better economic condition. RMIU is a new phenomenon recently occurring in middle China, which is totally different from urbanization pathways in eastern China. Regarding the driving forces behind the process of RMIU, the shift of manufacturing industries from developed coastal areas to middle China is a main contributor, which creating a lot of job opportunities for returning people. With such shift, many floating persons who once worked in coastal cities are returning their hometown or nearby cities for living and working. The kinship social network facilities such trend of migrant return, as they must solve their problems of kids’ education and the eldly care. So, economic factors are not the very important force underlying the current wave of returning migrants. In addition, some of them start up business in their hometowns, with market experiences and skills getting from the coastal China. This induces the endogenous development in Middle China. Finally, some policy implementations are highlighted, including rural revitalization, urbanization policy and urban transition.
Urban spatial structure is the form of interaction among the urban human-land relationship elements. Taking the Northeast 36 cities as the research area, using the more than 4 million Points of Interest (POI) grouped by industry types, the article used the kernel density estimation method, the diversity index method and the standard deviational ellipse method to analyze the urban spatial structure and the agglomeration characteristics of the various industries. This research found that the urban structure of Northeast China is mainly characterized by concentrated mass, dispersed combination, linear and radial types. Some cities have diversified spatial structure. The second industry and real estate industry in Northeast China show the characteristics of suburbanization, the development direction of each industry is consistent with the economic axis of the Northeast region, and most industries have not yet formed a specialized functional area; The centrifugal development of secondary industry and real estate industry is not strong for the shaping of concentrated block cities, but it contributes greatly to the spatial structure of dispersed group cities. Linear cities usually have a multi-center composite characteristics, the various industries of radial city are still biased towards centripetal aggregation. This research deepens the empirical researches of the big data-driven urban spatial structure as well as industry spatial pattern, and also provides scientific cognitive basis for the rational planning of urban space and the coordinated sustainable development in Northeast China during the revitalization period.
It is an important subject regarding sustainable urban development to promote and influence the coordination between ongoing economic development and the natural environment. From the perspective of resource consumption and environmental pollution, this article builds the evaluation index system of the urban resource and environmental pressure exploring the spatial and temporal characteristics of urban environmental pressure in the Pan-Yangtze River Delta region between 2000 and 2017. It also analyzes the threshold effects and mechanism of industrialization upon environmental pressure, based on the use of the panel threshold regression model. This paper has concluded three findings as follows. Firstly, the pressure in the region were experiencing a steady annual increase, with its growth rate following the rhythm of fast-medium-slow. Secondly, the environmental pressure of all cities had seen a steady increase year on year, though to varying degrees and at significantly different growth rates: the growth rates of economically backward areas were much faster than that of the economically developed cities. The cities with different types of environmental pressure formed the layout of extending from low pressure areas to high pressure areas, with the general pattern of ‘higher in the east and south, whilst lower in the west and north’. Thirdly, as the panel threshold regression model clearly shows, a significant threshold effect had taken place with regards to Economic growth, industrialization, population density. Consumption level, fixed asset investment, import and export trade exert a remarkable positive effect on environmental pressure. The reduction of energy intensity and the improvement of technological innovation are conducive to the reduction of pressure on resources and environment, whilst environmental regulation and energy consumption show no sign of a significant impact.
In the long-term evolution and competition, the spatial pattern of retailing industries reflects the rules of location selection and residents' needs. Based on POI data, the spatial pattern of retailing industries in Xi'an is analyzed. The spatial distribution pattern and agglomeration state of retailing industries sub sectors are analyzed by using Kernel density estimation, and bivariate spatial autocorrelation, nearest neighbor analysis method. The main conclusions are as follows: 1) Because of close relative to urban residents' daily life, retailing industries' spatial agglomeration reflects the distribution pattern of the urban center and the scope of the economically active area in Xi'an. The overall structure of the retailing industries in Xi'an is classical ‘center-periphery’, with the Bell Tower at the center, and the area within 16 km from the bell tower. The retailing industries act as a ‘single island’ in the four outer suburbs peripheral, Yanliang, Gaoling, Lintong and Huyi. 2) The spatial distribution characteristics of retailing are related to the residents' aligned consumption frequency. Products retailing with large daily consumption tend to be located in inner-city, while the product retailing with durable consumer goods, especially the products that need to occupy a large site, tend to be the peripheral area. The retailing of culture/sports goods and equipment, the retailing of textiles/clothing and daily necessities tend to distribute in inner-cities, while the retailing of automobiles, motorcycles, spare parts/fuel/other power, and the retailing of hardware, furniture and interior decoration materials are more inclined to distribute in the periphery area in Xi'an. 3) The comprehensive retailing, the retailing of food/beverage and tobacco products, the retailing of textiles/clothing and daily necessities, and the retailing of medicine and medical equipment tend to be centralized, to get close to consumers, and share the consumption market and space. While the retailing of automobile, motorcycle, spare parts/fuel/other power, and the retailing of hardware, furniture and interior decoration materials tends to be centralized itself obviously to share the brand effect. The spatial distribution of retailing outlets is obviously affected by traffic hubs, trunk lines, especially urban secondary roads.
Based on the context of Chinese analysis, this paper divides the spatial dimension into three levels: intra-provincial, provincial, and municipal, and puts forward two theoretical hypotheses: firstly, on the spatial scale of the municipal area, the spatial agglomeration is conducive to reducing regional income gap; secondly, at the provincial spatial scale, moderate spatial dispersion of factors is conducive to narrowing the regional income gap. This paper uses DMSP/OLS global nighttime light data to measure the urban spatial structure. We find that at municipal level, urban spatial structure expressed by the proportion of night light in the municipal jurisdiction, has a negative effect on the income gap. After controlling the exogenous influence of government behavior, industrial characteristics, and urban characteristics, and considering the self-inertia regional income gap, the conclusion is still robust. At provincial level, we find that the more concentrated the spatial structure of province, the greater the regional income gap. This conclusion is still robust after controlling the characteristics of provincial government, industry and nature. At intra-provincial level, Shanghai’s primacy ratio is positively correlated with the income gap of the Yangtze River Delta urban agglomeration, indicating that the more dispersed the intra-provincial urban spatial structure, the smaller the regional income gap. The above conclusions have important policy implications. From the perspective of narrowing the regional income gap, it is necessary to formulate appropriate urban development policies for different spatial scales.
Based on the cross-sectional data of 2005, 2010, 2015 and 2017, this article constructs a green development index system from 3 dimensions of green growth, green welfare and green wealth, using entropy weight TOPSIS evaluation method and obstacle model to explore the temporal and spatial evolution characteristics and obstacle factors of green development level in Jilin restricted development zone. The results show that: 1) From 2005 to 2017, the green development level of the restricted development zone in Jilin Province presented the time sequence evolution characteristic of "N" type fluctuation rising, and the overall green development level rises slowly, with an average annual growth rate of only 0.3%. 2) The green development level of the restricted development zone in Jilin Province had obvious spatial differentiation characteristics, which was high in the East, middle and low in the west, and the two-level differentiation characteristics were more obvious. 3) Per capita industrial added value, proportion of secondary industry output value, green coverage rate of built-up area, number of ordinary colleges and universities per 10 000 persons, per capita water resources and urban domestic sewage treatment rate were the main obstacle factors restricting the improvement of green development level of Development Zone in Jilin Province during the research period.
This article aims to analyze the spatial structure and its determinants of network positions of cities to serve the purposes of developing urban network theory and improving urbanization policy in China in the new era. Data on headquarter and branch locations of the largest 500 listed companies in China in 2016 are subjected to ownership linkage model to approximate the urban network, and regular equivalence block techniques are employed to generalizing about the configuration of position of cities in the system, leading to 15 blocks and 4 positions, i.e. primacy, broker, snob and isolates. Then the influence factors are examined by using 2 broad types of econometric models, i.e. ordinal logit model and multinomial logit model, and the mechanism is explored under the “behavior-structure-performance” conceptual framework of urban network growth. 4 main findings are concluded. First, the 15 blocks identified from applying the regular equivalent criterion can be allocated to 4 positions: 3 blocks occupy what Burt terms the primacy position, 5 blocks occupy the broker position, 3 blocks occupy the snob position, the rest 4 blocks are in the isolation position. Second, the image matrix resulting from the density criterion to the block-model density table reveals that the relationship among the blocks presents a core-peri periphery-periphery characteristics, in which the primacy blocks are located in the core, forming a high densely clique and playing the role of “headquarter cities”, the broker and snob blocks are located in the outskirt, while the isolation blocks are in the periphery, playing the role of “branch plant cities”. Third, market potential, key resources, location conditions and development basis are the key factors affecting the position of China's urban network. The improvement of economic scale, population size, political power, knowledge capital and network facilities will greatly enhance the network position in China, increasing the odds of cities being in the primacy position while decreasing the probability in the snob and isolate position. Fourth, the expansion of urban network space in China is a process of preferential attachment, geographical proximity and path dependence, which will further strengthen the power of cities with traditional advantages such as larger economic scale, rich political resources, etc. Under the environment of network development, China’s urbanization policy and urban governance system need to be adjusted accordingly. The Chinese government must actively respond to the possibly increasing gap between cities under the network environment and promote the cooperation between cities on a larger spatial scale.
In recent years, along with China’s growing ambitions to construct an innovative country and to leading economic power, sci-tech finance is receiving more and more attentions and has become one of the most essential engines of national social and economic development. Investigating optimum pattern of coupling and coordination of sci-tech finance system and regional economic development system is important and beneficial to their mutual and chronic growth in both micro- and macroeconomy levels. On the one hand, sci-tech finance gives rise to economic development by scientific and technological innovation; On the other hand, sci-tech finance contributes to realize the improvement and to upgrade of industrial structure by allocating of various resources, thereby to promote regional economic development. Coupling approaches have also been widely used in studying relationships between sci-tech finance and sci-tech innovation as well as regional economic development. However, there are few studies focusing on the interaction between sci-tech finance system and regional economic development system. Most of current studies regard sci-tech finance as merely an affiliated product of economic development. In order to better elucidate relationshipd between sci-tech finance and regional economic development, the evaluation system of coupling sci-tech finance and regional economic growth was established in this study based on 30 provinces and cities in China from 2005 to 2015. Using grey relative analysis (GRA), correlation and coupling levels of each element of the two systems were quantitively assessed. Coupling and coupling-coordinating degree models were then established and sorted according to the coupling and coordinating types of sci-tech finance and economic development. Temporal and spatial coupling characteristics of the two systems were subsequently analyzed. Results indicated that correlations between sci-tech for finance and economic development ranged from medium to high level during the study period. Sci-tech talent and grant were the two important factors that significantly drove the economic development. It was also found that sci-tech finance highly depended on both import and export trade. Within the study period, the coupling system between sci-tech finance and regional economic development experienced three stages, which fluctuated increased from 2005 to 2008, continuously decreased from 2008 to 2011, and slowly increased from 2011 to 2015, respectively. The coupling and coordinating degree between sci-tech finance and economic development was at the initial stage and represented significant regional differences, with the ‘three step descending’ variation law of ‘coastal area -the Yangtze River Economic Belt-inland area’, and with the spatial pattern of high degree in eastern and central regions and low degree in western, southern and northern regions. Based on all results above, suggestions were finally presented in terms of further improving benign interaction of the coupling and coordination systems.
Urban system and network are the hot topics of worldwide urban and regional research. There is a plenthora of literature on the urban network from the perspective of passenger, information and business flow. But there is a big gap in the urban network from the perspective freight flow. This article analyzed the hierarchical structure, spatial differentiation, spatial connection and evolution characteristics of Chinese urban networks using the interlocking network model, which is established by the theory of global urban networks. The network data of China's top 100 logistics enterprises in 2007, 2012 and 2017 is introduced into the model. Results indicated that the urban network of China based on logistics enterprise data was hierarchically characterized obviously. And presented a regional spatial structure of ‘two main and multi-center’. The discrete level of network connection was in gradually decreasing, its stability and balance were increasing, and the hierarchical structure tended to be reasonable. The spatial differentiation of organizational capacity of each node city was obvious, and the organizational capacity of Beijing-Tianjin-Hebei Region, the Yangtze River Delta and the Pearl River Delta were continuously at a high level in comparison. There was a trend of synergistic development among cities. In terms of urban network connection abd the linkage status of urban logistics networks along the Yangtze River rises, Shanghai, as the center of the T type space structure, is replaced with Beijing as the center of the core network structure. Taking Hu Line as the boundary, a dense spatial pattern in the East and relatively sparse in the west part had been formed. And it concluded that the spatial pattern evolved from hierarchical network connection to hierarchical and spatial proximity network connection.
Based on the fifth and sixth Population Census data, this paper uses Exploratory Data Analysis (ESDA) and spatial econometric model to analyze the spatial pattern evolution characteristics and driving factors of China's prefecture population aging. The conclusions are as follows: 1) The Hu Line is a significant dividing line of the overall pattern of China's population aging rate between the east-high and low-west. The regions with a high population aging rate in China are located to the east of the Hu Line, and the lower regions are located to the west of the Hu Line. As the aging population continues to increase, the spatial pattern of the initial population aging from the west to the east gradually changed. 2) China's population aging has a strong spatial positive correlation, showing the spatial distribution characteristics of high-high and low-low similarity aggregation. The high-high agglomeration areas are mainly distributed in the Yangtze River Delta, Sichuan Province and Chongqing, Shandong Peninsula, Middle and South Liaoning Province, etc. The low-low agglomeration areas are mainly distributed in northwestern China, southwestern China, western China, and some prefecture-level cities of the Pearl River Delta. This positive spatial agglomeration has weakened over the past 10 years. 3)The spatial pattern of China's population aging is influenced by population factors and social and economic factors. Among them, the birth rate, mortality rate, education level and population density factors are significant, while the first three factors are always the determinants of population aging. Therefore the demographic factors are the direct factors affecting the evolution of the spatial pattern of China's population aging and the imbalance factors of social and economic development are the root cause. To this end, the recommendations on population aging are proposed from the aspects of population factors and social and economic factors.
With development of urban society and economy, increasing emissions of water pollutants have led to water environment deterioration and restricted city’s sustainable development. In this paper, Ningbo city was selected to evaluate water environmental effects by two aspects on water environmental sensitivity and present water quality. With the differences on the population agglomeration level, type of industry development, water pollution treatment capacity, and the index of water environment effects are decreasing from the city center to the periphery. The method of exploratory spatial data analysis (ESDA) is used to explore the spatial heterogeneity of evaluation units. The geographical weighted regression (GWR) indicated the quantitative analyses on the influence mechanism of water environment effects. Among influencing factors, economic development level was the predominant drivers of urban water environment change. At the meanwhile, industrial development and population agglomeration have been identified as direct causes of water environment pressure. They have significant positive impacts on water environmental effects. Spatial layout and dominant industry types of industrial parks had greater impacts on water environment effects than the other factors, and this presented issues that needed special attention for control water environmental pollution in future. By regulating the industry access threshold and spatial distribution of different development types, the ecological function zoning can effectively prevent negative effects of industry development on urban water environments. The present work can provide scientific basis for deciphering coordinated effects between water environmental protection and urban economic sustainable development, and can promote the improvement of water environment quality.
Promoting the transformation of economic growth mode by ‘vacating cage to change birds, phoenix nirvana’ is an important feature of General Secretary Xi Jinping's political thought of governing the country. Beijing has started a major shift from ‘accumulating resources for growth’ to ‘resolving functions for development’ along with the Beijing-Tianjin-Hebei coordinated development. The goal is to ‘vacating cage to change birds’, achieve industrial transformation upgrading, and accelerate the construction of ‘high-precision’. The economic structure enhances the quality of urban development and the quality of life of the people. However, ‘vacating cage’ is not only ‘emptying cage’. It is not simply a matter of ‘replacing small and old’. Only if the ‘old bird’ and ‘new bird’ are flying together, the ‘real’ and ‘virtual’ industries are mutually benefited. Equal emphasis, the new and old kinetic energy can be smoothly converted. Therefore, this article analyzes the status of the industry transformation and upgrading of Beijing's ‘vacating cage to change birds’, the question of where the ‘new bird’ enters the ‘old bird’, the rational optimization of the ‘old cage’ space structure, and the ‘old bird’ nirvana ‘new bird’ based on, ‘old birds’ and ‘new cages’ to undertake, the article proposes the ideas and paths for the industry transformation and upgradation of Beijing's ‘vacating and changing birds’. The possibilities of the industry transformation and upgradation of the ‘vacating cage to change birds’ are as followed: 1) It should be based on the construction of a ‘high-precision’ economic structure. 2) The fundamental driving force of adhering to the ‘innovation-driven’ development strategy. 3) To improve ‘Environmental civilization’ environmental quality is the guiding ideology. 4) To promote the coordinated development of ‘Beijing-Tianjin-Hebei’ as the depth direction. The path of the future industry transformation and upgradation of the ‘vacating cage to change birds’ is as belowed: 1) Improve the cooperation of the Beijing-Tianjin-Hebei industrial chain, and expand the regional linkage development space by ‘vacating cage to change birds’; 2) Merge the east-west city into the capital zone, ‘vacating cage to change birds’ protect Beijing's historical and cultural city; 3) Practically exert the role of government functions, ‘vacating cage to change birds’ to enhance the internal dynamic mechanism of the enterprise; 4) Plan to build a ‘micro-center’ small town, and ‘vacating cage to change birds’ to promote the effective deconstruction of Beijing's population.
Topography is an important factor affecting regional population distribution and social and economic development, and its influence and restraint effect is more obvious especially in mountainous areas. This study takes Qinba Mountain area as an example to analyze the pattern and differentiation characteristics of population and economic space on multiple scales with the help of a variety of spatial analysis and geostatistics methods. Based on 90 m resolution SRTM data, it extracts elevation and relief amplitude, with an emphasis on quantitatively revealing the relationship and influence degree between terrain and environmental elements and the population and economic space. The results show that: 1) The population, village and economic density of Qinba Mountain area show a significant differentiation. The results of Lorenz curve and Gini coefficient show that the population distribution is unbalanced, but the unbalance degree is lower than the national level. Besides, the results of Moran's index show that population and economic space have certain agglomerating characteristics, and the degree of agglomeration is more obvious at the cell scale. 2) The density of population and GDP shows the spatial pattern of external heat and internal cooling, and it is found that the differentiation of population and economic factors in the vertical direction is obvious through the analysis of spatial element density in the cell scale. 3) The change curve of the density of population and GDP and elevation in sample belt research show a reverse correlated relationship, and the population and economy have a certain adaptability to terrain in small scale range. 4) Economic development is more dependent on terrain conditions, and the adaptability of population and villages to topography is more obvious; the vertical differentiation of topography leads to the spatial difference of natural environment and regional development conditions, and then affects the spatial distribution pattern of population and economy.
The study of social inherent vulnerability (SIV) is not only helpful to understand the sustainable development states of regional social system, but also to seek appropriate countermeasures to improve the adaptability of social system. In view of this, this paper constructed an analytical framework of SIV and took Gannan Plateau, a tipical ecological fragile area which locdted in the farming-pastoral areas on the Tibet Plateau, as the study area. On the basis of comprehensively evaluating the inherent vulnerability of rural society and analyzing its spatial differentiation characteristics, this paper identified its key factors. The results showed that: 1)The inherent vulnerability of rural society in Gannan Plateau was ‘shuttle-shaped’, in which high, moderate and low vulnerability villages accounted for 18.95%, 47.37% and 33.68% respectively. 2)There were obvious regional differences in the SIV. From the perspective of the farming areas-farming-pastoral areas-pastoral area and alpine canyon areas-mountain hilly areas-hilly plateau area, the SIV tended to increase; At the same time, the SIV tended to decrease as the degree of ethnic minority inhabitation decreased and the level of economic development rises. 3)The SIV was distributed unevenly in ‘the north high and south low’, while the sensitivity was ‘high in the middle and low around’, and the adaptability was relatively balanced ‘fragmented’ distribution. 4)Temperature, fertility structure, ethnic structure, housing security, social vulnerable group proportion, economic condition, information availability and the proportion of insurance participation were the key factors affecting the SIV. Finally, the corresponding countermeasures and suggestions for different key factors were put forward.
The SST data for IPCC RCP2.6, RCP4.5 and RCP8.5 are selected from the Canadian Earth System Model of the CCCma (CanESM2) of CMIP5(Coupled Model Intercomparison Project Phase 5), which is more suitable for the area of South China Sea. Based on the coral reef pixels of Nansha archipelagoes and the linear regression method, the summer SST rising trend in each RCP scenario was analyzed for the South China Sea Islands. Moreover, the temporary refugia in the RCP scenarios were investigated based on two thermal stress indexes of Degree Heating Weeks (DHW) and the onset of annual bleaching conditions. The main results are as following: 1) In three RCP scenarios, the apparently warming reef areas are the Nansha Islands; 2) The proportion of coral reefs projected to experience annual bleaching conditions not later than the global median year is 17%, 29% and 42% in RCP2.6, RCP4.5 and RCP8.5 scenarios respectively. These reefs are located in the Nansha Islands; 3) Reefs of Xisha Islands, Zhongsha Islands, Dongsha Islands and the northern Nansha Islands in the higher latitudes are the future temporary refuges. This article supplements the global temporary refugia in a warming world and proves the important role of the South China Sea Islands in the future global coral reef sustainability, which is also of great significance for mitigating greenhouse gas emissions and coping with climate change.
We analyzed the spatial-temporal changes in global vegetation and their dynamic responses to temperature and precipitation using GLASS-LAI (Global Land Surface Satellite-Leaf Area Index ) and CRU (Climatic Research Unit) meteorological data from 1982 to 2015. The results showed that: 1) Global vegetation showed an overall greening trend, which is paricularly significant over grasslands, savannas, evergreen broadleaf forests and woody savanas. Grasslands have the largest greening and browning area, indicating their vulnerability to climate. 2) In terms of the inter-annual relationships, the LAI of grasslands and open shrublands were overall positively correlated with precipitation, while temperature had different effects on the growth of vegetation at diverse latitudes. This could be attributed to that, the growth of vegetation at middle and low latitudes was inhibited by the increasing temperature, while facilitated by the rising temperature at high latitudes. 3) In terms of the intra-annual relationships, precipitation and temperature together promoted vegetation growth in the southern hemisphere, however, the vegetation in the northern hemisphere was mainly affected by precipitation, except evergreen broadleaf forests. 4) The results of stepwise multiple regression indicated that the rising instant temperature had positive influence on the growth of evergreen broadleaf forests, mixed forests, and croplands, while woody savannas and savannas were significantly impacted by the instant precipitation.
Based on 26 of the Weihe River Basin from 1961 to 2016 in the daily precipitation data of weather stations, the selection is closely related to the extreme precipitation events 9 index, using the method of linear trend, Mann Kendall mutation point test and variance analysis, reveals the tendency of the extreme precipitation events, mutation of the Weihe River Basin and on, the precipitation of the middle and lower reaches of Weihe River Basin the differences of characteristics of extreme precipitation events for the study area in the future to provide scientific prediction and theory reference. The results showed that: 1) The annual total precipitation in the upper, middle and lower reaches of the Weihe River Basin and the whole basin decreased at the rates of 16.588 mm/10a, 8.319 mm/10a, 6.703 mm/10a and 9.544 mm/10a, respectively, indicating that the total precipitation in the Weihe River Basin has been decreasing year by year in the past 56 years, and the whole Weihe river Basin has been drying up. 2) Precipitation intensity (SDII), heavy rain amount (R95PTOT) and extreme precipitation amount (R99PTOT) tend to rise on the whole, extreme precipitation amount rise higher than the strong precipitation, rise higher than the middle and lower reaches area of the upstream region, shows that the strength of the Weihe River Basin in extreme precipitation increased, the extreme precipitation event frequency is increased. 3) The years of extreme precipitation events in the Weihe River Basin were concentrated in the 1990s and the early 21st century, and the inter-annual differences in precipitation were large, with more obvious changes in the middle reaches. 4) According to the results of relevant analysis, it is concluded that the middle and lower reaches of the basin to the occurrence of extreme precipitation events play a greater role.
Urban heat island (UHI), defined as a human-induced urban climate phenomena characterized by higher temperatures in urban areas than in their surrounding rural areas, is widely acknowledged as one of the most significant urban environmental problems caused by urbanization. Urbanization has significantly transformed natural and semi-natural surfaces into impervious urban structures, which has disturbed the balance of the Earth's surface radiation and energy, as well as the composition of the atmospheric structure in the near-surface. Many studies have explored the complex mechanisms of urban heat islands by examining the relationship between land surface temperature and land surface factors. Few, however, have explored the relative contributions of impact factors to urban thermal environment using spatial statistical analysis. In addition, referring to the heterogeneity of urban land surface characteristics, the relationship between urban thermal environment and the related land surface factors is expected to be different within urban area.In order to explore the influence mechanism of related land surface factors on urban heat island intensity at various locations, Xiamen city is taken as an example. Based on remote sensing images and building census data, the concept of Local Climate Zone (LCZ) and spatial autocorrelation concept are applied to analyze the spatial response rules between related surface factors and heat island intensity in all LCZs. Spatial autoregressive model is used to quantitatively analyze the spatial relationship between heat island intensity and related land surface factors in LCZs of Xiamen. The results show that: 1) Heat island intensity in the study area has significant positive spatial correlation and obvious spatial agglomeration. The high value area concentrates on the construction land, cultivated land and bare land in the east and south, while the low value area concentrates on lakes, rivers and other water bodies, wetlands and forest in the north and northwest. 2) Ordinary linear regression model(OLS) can not effectively explain the relationship between related surface factors and heat island intensity in space. The spatial lag model(SLM) and spatial error model(SEM) results are compared with the OLS, which shows the best performance of the SLM and SEM model. By comparing the R 2, AIC, SC, and LIK values, it can be seen that the SEM model has better fitting effect than spatial lag model, which can more scientifically analyze the spatial relationship between surface factors and heat island intensity. 3) In the SEM Model, lambda is always positive and significant in all LCZs, indicating strong spatial dependence of model error. In the SLM Model, the positive and significant spatial autoregressive coefficients indicate an active influence from neighboring regions. 4) The land surface factors which can be independent variables of the regression model are different in each LCZ. In all LCZs, as independent variables of the regression model, vegetation index, water index and sky view factor show a negative correlation with urban heat island intensity, while building density and proportion of impervious water surface show a positive correlation with urban heat island intensity. However, the correlation between building volume density, average building height, building height difference and heat island intensity is not consistent in various LCZs. To a certain degree, the mathematical relationship between urban heat island intensity and land surface factors is discussed. According to the research conclusions, it is suggested to protect the "compensation area" and separate the "function area", optimize the land use structure. In addition, it is necessary to consider the difficulty of adjusting land surface factors, cooling efficiency and population density to determine feasible planning strategies.
During detailed field investigations, a complete and continuous Holocene soil and sediment profile (SLJ) was identified in the northern part of the Lajia Ruins. On the basis of field pedo-sedimentological observation and descriptions, as well as physic-chemical analysis and OSL dating on the soil and sediment samples, a complete pedo-stratigraphic sequence was established in the ruins. Meanwhile, the cause of sediment overlying the Lajia Settlement of the Qijia Culture was revealed through in-depth analysis of soil sediment properties and surface processes. The results show that the pedo-stratigraphic sequence of the profile includes the modern soil (MS, 0-1.50 ka B.P.) -the recent loess (L0, 1.50-3.10 ka B.P.) -a composite palaeosol layer (S0, 3.10-8.50 ka B.P.)-transitional loess (Lt, 8.50-11.50 ka B.P.)-the Malan Loess (L1, >11.50 ka B.P.). The mid-Holocene palaeosol (S0) is intercalated by three thin intervals of red clay (RC3, RC2, RC1) and the flashflood deposit (FFD), and thus subdivided into four sub-layers (S0-upper, S0-upper middle, S0-lower middle, S0-lower). This proves that there was a prevailing period of flashfloods and mudflows in the development of palaeosol, which is dated by OSL as 3.96-3.65 ka, corresponding to14C ages of 3.85-3.60 ka B.P.. During this period, the large-scale rainstorm-induced flashfloods and mudflows were thus triggered in the headwaters of the gullies, and overflowed the trenches at the front of the ancient diluvial fan of Great Red Hills and spread over the land of the second terrace of the Yellow River. The Lajia Settlement of the Qijia Culture and the adjacent farmland were overtaken by the first rainstorm-induced flashfloods and mudflows during which women and children were killed in their dwellings.
