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Articles online first have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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Driving effect of land use change on ecosystem services— A case study of Qinling Nature Reserves
LI Zhuo, HOU Peng, JIANG Weiguo, WANG Xiaoya, HOU Jing, CHEN Yan, ZHU Hanshou
doi:10.12202/j.0476-0301.2022034
Abstract(3) HTML(1) PDF (5081KB)(0)
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Taking 14 Qinling Nature Reserves as an example, based on five periods of land use, meteorology and soil data in 2000, 2007, 2010, 2015 and 2020, this research analyzed the impact of land use change on the spatiotemporal changes of water yield, soil conservation and habitat quality. The results were as follows: (1) From 2000-2020, the proportion of forest and grassland area in 14 Qinling Nature Reserves increased from 92.77% to 94.50%, and the forest and grassland area in the core area reached 99.14% in 2020; (2) From 2000-2020, water yield and soil conservation function in the reserves showed a change trend of first increasing and then decreasing, while habitat quality was a change process of first decreasing and then increasing. Habitat quality was more susceptible to land use change than water yield and soil conservation function; (3) There was a large area of cultivated land and wetland in Hanzhongzhuhuan Reserve, which caused its water yield function to be high, while the soil conservation function and habitat quality were low. Although other reserves have been damaged and occupied during the study period, they have been basically restored in 2020. Qinling Nature Reserve is an important protected area in China. With the continuous strengthening of protection, the ecological environment in the reserve has been improved, but it is still necessary to strengthen monitoring and control.
Marginal abatement cost analysis of urban carbon neutralization measures
LIU Gengyuan, GUO Lisi, CHEN Yu, YAN Ningyu, MENG Fanxin, LI Hui, CHEN Caocao, XIE Tao
doi:10.12202/j.0476-0301.2022212
Abstract(1) HTML(1) PDF (1295KB)(0)
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Cities are the main site for achieving carbon neutrality. Under the carbon neutrality target, more emission reduction technologies and policies will be encouraged to play a role in the low carbon transformation of cities. This study uses the marginal abatement cost method to analyze the abatement potential and cost of specific abatement technologies in the context of low-carbon measures promotion in Beijing. The marginal abatement cost curve for Beijing with 35 abatement measures is drawn, and priority abatement measures with high economic efficiency are identified. This study also provides a prioritization of technology measures and implementation paths for Beijing to achieve the carbon neutrality goal. The results show that: 1) the screening of emission reduction technologies for the power sector, transportation sector, and building sector has an emission reduction potential of 1,496 million tons, 766 million tons, and 255 million tons, respectively. The average marginal carbon abatement cost is 485.12 yuan/ton, and the average abatement costs of the power sector, transportation sector and construction sector are 154.56, 417.56 and 688.28 yuan/ton. Beijing should greatly promote power abatement measures to ensure that Beijing's carbon emissions enter a rapid decline; (2) Among the 35 emission reduction measures, the marginal abatement cost of 9 of them is negative, and the cost-effective abatement potential is 399.67 million tCO2, accounting for 39.15%. Negative cost measures such as electric cabs, electric buses and electric light trucks, and lighting energy efficiency should be vigorously promoted at the early stage of emission reduction; (3) High marginal abatement cost measures have high abatement potential, but the implementation is difficult due to cost barriers. To promote the proliferation of such abatement technologies, the government can adopt a certain degree of subsidies or incentive policies to ensure the stability of abatement investment returns and reduce the risk of abatement investment.
Spatial and Temporal Dynamic Distribution of Extreme Rainstorm in Beijing Based on UMAP and HDBSCAN
XU Shugao, WANG Xianyang, JIANG Weiwei, YU Jingshan, LIU Yuan, ZHOU Guihuan
doi:10.12202/j.0476-0301.2022303
Abstract(24) HTML(10) PDF (11120KB)(3)
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Extreme rainstorm has the characteristics of short duration, strong rain and strong destructiveness, which is one of the main causes of flash flood and waterlogging disasters. Exploring the spatial and temporal dynamic distribution of extreme rainstorm is helpful to predict its development process. In this study, a method of clustering combined with dimensionality reduction algorithm was proposed to extract the spatial and temporal dynamic characteristics of extreme rainstorm events. Using the precipitation data of 308 meteorological stations in Beijing from 2004 to 2016, the spatial and temporal dynamic distribution models of various extreme rainstorm events were constructed by introducing HDBSCAN clustering method. Combined with the UMAP dimensionality reduction algorithm, four types of extreme rainstorm models in Beijing were extracted for the first time : 1) Mode 1: Rainstorm concentrated in the main urban area, moving slowly around the main urban area ; 2) Mode 2: Rainstorm moves from the southwest mountainous area through the main urban area to the northeast ; 3) Mode 3: the rainstorm spreads from the western mountainous area to the northwest of the city, and finally moves to the north of the city ; 4) Mode 4: Torrential rain moves westward from western mountain area to urban area. The results show that the main type of extreme rainstorm in Beijing is short-duration precipitation, and the rainstorm center has a tendency to move from west to east in space. Among them, the downtown area, the southeastern mountainous area and the southern plain area face relatively higher extreme precipitation risks. The physical mechanism of model characteristics of all kinds of extreme rainfall is clear, and the reconstruction characteristics of rainfall events can fully represent the actual rainfall events. This study can provide an important basis for flood forecasting and scientific management in Beijing.
A Novel Geometric Design of Annular Absorber for Improving the Detection Efficiency of Compton Camera
YANG Hao, YUAN Ziquan, XUE Dongyang, JIANG Jianyong
doi:10.12202/j.0476-0301.2022248
Abstract(19) HTML(3) PDF (3894KB)(5)
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Compton camera is widely used in various applications. In this paper, a novel high sensitivity Compton camera with an annular absorber was proposed and its effectiveness was demonstrated via Geant4 simulation. The detection efficiency and angular resolution of the novel Compton camera were estimated and compared with a traditional Compton camera with two planar detectors. The scatterer of the two Compton camera were identical and consisted of 8×8 Ce:Gd3(Al, Ga)5O12(GAGG) scintillator detector, each measuring 1×1×0.5 cm3. The absorber of the traditional camera contained 8×8 GAGG scintillator detector, each measuring 1×1×1 cm3. The absorber of the novel camera contained sixty-four GAGG crystals (each of 1×1×1 cm3), which were arranged in an annular shape with an inner radius of 5.15 cm and an outer radius of 7.39 cm. Simulation results show that with comparable or even better angular resolution, the novel Compton camera significantly enhanced the effective detection efficiency. Experimentally results demonstrated that when the distance between the scatterer and the absorber is larger than 11.4 cm, the enhancement of the detection efficiency is over 1-fold.
Parameterization of tropical cyclones landing intensity-precipitation at various scales for probable maximum coastal flood scenario development
ZHANG Haixia, CHENG Meng, FANG Weihua, TONG Xingwei
doi:10.12202/j.0476-0301.2022315
Abstract(26) HTML(10) PDF (1767KB)(4)
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To carry out the setting of the probable maximum flood-storm surge composite disaster scenario, we add the parameter of tropical cyclone precipitation to the previous studies on the setting parameters of probable maximum tropical cyclone. Thus, the process of constructing a methodological framework for setting tropical cyclone intensity-precipitation parameters is explored. Based on the best track dataset of tropical cyclones from the China Meteorological Administration, the radius of maximum winds from the Joint Typhoon Warning Center, and the precipitation data obtained by fusing observations from Chinese automatic stations with CMORPH products, we statistically analyzed the quantitative relationships between key parameters of tropical cyclones and constructed a method for setting parameters such as maximum sustained wind, central minimum pressure, the radius of maximum wind, and hourly precipitation. It is found that, based on previous methods for setting parameters for probable maximum tropical cyclones, the addition of precipitation as a meteorological parameter can better develop the critical parameters for different levels of tropical cyclone landfall and provide input data for probable maximum flood-storm surge composite scenarios. Then, the upper limit of the probable maximum intensity can be effectively determined by a linear fit of the parameter relationship plus multiple standard deviations. The central maximum wind speed is negatively correlated with the central minimum pressure and the radius of maximum wind. There is a significant negative outer envelope correlation with the maximum hourly precipitation, 99th percentile of hourly precipitation, and total hourly precipitation. In addition, if the sample distribution is scattered, the uncertainty of the data distribution and the correlation between the parameters can be explored by a combination of interval discussion and extreme value function fitting, based on which total hourly precipitation at different probability levels and the outer envelope are investigated. The results of this study can provide a basis for decision-making on tropical cyclone prevention, mitigation, relief, and risk management in coastal areas.
Drivers and decoupling effects of carbon emissions in Northwest China
TENG Wangtengfei, FENG Taozhu, GUO Daoyan
doi:10.12202/j.0476-0301.2022278
Abstract(19) HTML(3) PDF (2124KB)(2)
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The contradiction between the demand of rapid economic growth and the “double carbon” target in Northwest China is an important problem to be solved. The article selects the data of Northwest China from 2011 to 2019, adopts the carbon emission coefficient method to account for the carbon emissions of energy consumption, and uses the LMDI method to study the influence of energy structure, energy intensity, economic output and population size on the carbon emission level. . The study shows that (1) Shaanxi Province is the largest province in northwest China in terms of carbon emissions, followed by Xinjiang, Gansu, Ningxia and Qinghai. (2) Economic output and population size will promote carbon emissions, and the impact of population size on carbon emissions is smaller compared with economic output; energy intensity will promote carbon emission reduction; and the role of energy structure on carbon emissions has two sides. (3) The decoupling relationships of total carbon emission, carbon emission intensity, per capita carbon emission and economic development all tend to change to strong decoupling; Shaanxi, Gansu, Xinjiang and Qinghai achieve strong decoupling of total carbon emission, carbon emission intensity, per capita carbon emission and economic development. The findings enrich the research related to carbon emission drivers and decoupling effects, and provide targeted policy recommendations for coordinating regional economic development and reducing carbon emissions in Northwest China.
Bergman metric on a class of tubular domains
LIU Jiaxin, DENG Guantie, YIN Hongheng
doi:10.12202/j.0476-0301.2022295
Abstract(29) HTML(12) PDF (517KB)(6)
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In this paper, we gives the bounded condition of two types of integral operators; The Bergman metric on the tubular area \begin{document}$\varOmega$\end{document} is calculated; A set of metric spheres covered by \begin{document}$\varOmega$\end{document} is obtained; It is proved that the measure \begin{document}$\mu$\end{document} on the tubular domain is some equivalent condition of the Carleson measure.
Detection and attribution analysis of hotspots of ecosystem gross primary production change in China
ZHAO Quanbo, ZHU Xiufang, XIE Tian, YAN Chenyi
doi:10.12202/j.0476-0301.2021101
Abstract(466) HTML(191) PDF (1314KB)(82)
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Terrestrial gross primary production(GPP) is a key process for understanding land ecosystems dynamics. Detecting the hotspots of GPP change and analyzing its impact factors are helpful to understand the process of ecosystem carbon cycle and provide reference for ecological environment protection and management. This study combines trend analysis and hotspot analysis to detect hotspots of GPP changes in China and analyzes the impact of natural factors and human activities on GPP changes. We found that GPP has an increasing trend from 1982 to 2017 in China, with an average change of 1.92gC·m−2·a−1. The hotspots with significant positive GPP change are located in the eastern Qinghai-Tibet Plateau, the Loess Plateau, the North China Plain and the Yunnan-Guizhou Plateau. The hotspots with significant negative GPP change are located in the southern part of Tibet, the Yangtze River Delta and the southeast coastal areas. The combined influence of temperature, precipitation and radiation on GPP is greater than that of single natural factor, in which the correlation between temperature and GPP is the highest. The proportion of pixels with temperature and human activities as the dominant factors of GPP change was the highest, accounting for 43.86%, followed by temperature (26.86%). The influence of temperature and human activities differs in different hotspots. On the whole, they played a positive role in four GPP increasing hotspots and a negative role in three GPP decreasing hotspots.
Display Method:
Lower deviations for general supercritical branching process with immigration
XIE Chunyan, ZHANG Mei
2023, 59(1): 1-8. doi:10.12202/j.0476-0301.2021268
Abstract(109) HTML(54) PDF (695KB)(27)
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For a supercritical branching process with immigration \begin{document}$(Z_{{n}})$\end{document} , a sequence of constant \begin{document}$c_{{n}}$\end{document} could be used to describe the growth rate of the process.The asymptotic behavior of \begin{document}$ P(Z_n=k_n) $\end{document} \begin{document}$ (k_n=o(c_n)) $\end{document} is called the lower deviation probability of \begin{document}$ Z_n $\end{document} .In this paper, under \begin{document}$ EZ_1 \ln Z_1=\infty $\end{document} , first, a local limit theorem of \begin{document}$ Z_n $\end{document} is proved.Then in the Schröder and Böttcher cases, the lower deviation probability \begin{document}$ P(Z_n=k_n) $\end{document} is discussed, which improves and generalizes the corresponding results in the literature.
Synchronized modes of coupled oscillator system on liquid surface
DONG Wei, TONG Haoxuan, ZHANG Haoyue, PENG Yunru, DI Zengru
2023, 59(1): 9-12. doi:10.12202/j.0476-0301.2022226
Abstract(53) HTML(23) PDF (2755KB)(17)
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In this article, a coupled oscillator system model was adopted, and its dynamics equations were numerically simulated with MATLAB.The initial conditions of the system determined the synchronization mode when the system reached steady state.Simulation on viscous resistance of liquid and quality of coupling plate showed that viscous resistance was positively correlated with probability of anti-phase synchronization, mass of coupling plate was negatively correlated with probability of anti-phase synchronization in steady state.In terms of relaxation time, it was found that average relaxation time of in-phase synchronization was slower than anti-phase synchronization.A coupled oscillator system was set up on the surface of the liquid, and three kinds of liquid with different viscosity coefficients, water, salt water with a concentration of 10% and cooking oil, were used.Experimental results are qualitatively consistent with numerical simulations.
Perceptual learning enhanced the coding capacity of primary visual cortex in rhesus monkey
LIU Zhaofan, WANG Dahui
2023, 59(1): 13-18. doi:10.12202/j.0476-0301.2022204
Abstract(0) HTML(0) PDF (2573KB)(0)
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Perceptual training was found to reduce variability of primary visual cortex (V1) in rhesus monkey neuron response among different trials with identical stimulus, indicating response to the same stimulus became more stable.Meanwhile, correlation between neuronal activities was found to be decreased, indicating that activities between neurons became more independent, and perceptual training increased the dimensionality of neural population, thus improved capacity of neuronal representation information.Therefore, perceptual training increased stability of neuronal response to stimuli, reduced redundant neural activities, increased capacity of neuronal information representation, and improved perceptual ability.
Studies on a TPC gaseous detector
ZHANG Yaofeng, YIN Yuan, CAO Lei, LIU Rong, LIU Lin, ZHANG Chunlei
2023, 59(1): 19-24. doi:10.12202/j.0476-0301.2022009
Abstract(131) HTML(83) PDF (3442KB)(36)
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A TPC gas detector was designed and fabricated.Firstly, the field cage was made with printed circuit board plates, which include some accurately located strip electrodes, so as to achieve uniformly distributed electric field in the drift region.Three layers of wire electrodes were assembled in the avalanche region.The identical potential distribution of electric field in different layers of wire electrodes were calculated, and the technologies of wire electrode wielding, tension application on wire electrodes, detector working mode transferring from trigger-on to trigger-off and vice versa were examined.Then, a DPC resistor array was used to simplify readout circuit from 400 to 4 outputs, and the calibrations of array for each node pad were carried out.Lastly, the experiments by the detector for the cosmic ray test was done.The corresponding wave form data agreed well with simulation results, and the transverse positions for these ionization events were also measured.All the work will help a lot to develop this kind of TPC detectors and to do the related experiments.
Pre-study of LAMOST-Kepler/K2 project based on improvements in astronomical site conditions
HU Xueying, FU Jianning
2023, 59(1): 25-30. doi:10.12202/j.0476-0301.2022340
Abstract(66) HTML(19) PDF (1567KB)(17)
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To take full advantage of time-series ultra-high precision photometric data for about 800000 stars obtained during the Kepler space telescope’s mission in 2009-2018, the LAMOST telescope began to carry out low-resolution spectroscopic observations for stars in Kepler (K1) and K2 fields in 2012 and 2015, known as the LK1 and LK2 projects, respectively.After making stastistic analysis on the observed target coverage rates of the LK1 and LK2 projects the improvements of the two projects under better astronomical site conditions were predicted.Until June 2021, LAMOST’s coverage of the K1 sky area has reached 43%, and that of observable targets in the K2 sky area has reached 38%.If the seeing condition, sky background and observable night numbers could be improved at a new site, the coverage of LAMOST observations for K1 targets will reach 80% in two observational seasons, and that for K2 targets will reach 70% after four observational seasons.
Mode change characteristics of PSR J0826+2637
LIN Quanwei, DANG Shijun, ZHI Qijun, BAI Juntao, XU Xin
2023, 59(1): 31-37. doi:10.12202/j.0476-0301.2022067
Abstract(66) HTML(22) PDF (3092KB)(12)
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The FAST observation data at center frequency of 1.25 GHz are used to analyze energy distribution and modulation characteristics of single pulse of PSR J0826+2637.A new mode change is found, average pulse profile and polarization characteristics of different modes are discussed.Strong and weak modes are present in B mode, a PN phenomenon is found in weak mode, with NF of 2.7%.In both strong and weak modes, polarization results of inter-pulse are slightly different, while the main pulse changes greatly.The mode change characteristics of PSR J0826+2637 are difficult to explain with existing models.
The molecular classification of adult diffuse glioma: a review
FAN Xiaolong, YANG Zichen
2023, 59(1): 38-42. doi:10.12202/j.0476-0301.2022153
Abstract(0) HTML(0) PDF (399KB)(0)
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Starting from the Classification Instruction of 2007 World Health Organization, this work review developments in molecular classification of adult diffuse glioma in the past two decades.A significant change in the classification scheme of glioma occurred: from clinical and histological classification to molecular classification combined with physiology.Some of the discoveries in molecular characteristics of glioma and karyotype features have prompted the classification schemes to deepen into the nature of glioma.On top of this, the classification scheme based on models of development of brain, rather than classification scheme based on histology, will be the future direction of glioma classification.
Herbicide acetochlor inhibits adrenergic receptor-mediated calcium oscillations in rat hepatocytes
LIU Fangyuan, ZHANG Binbin, CUI Zongjie
2023, 59(1): 43-55. doi:10.12202/j.0476-0301.2022145
Abstract(0) HTML(0) PDF (3309KB)(0)
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Herbicide acetochlor after application enters both surface and underground waters, so that acetochlor concentrations in rivers and streams could be sufficiently high (nmol·L−1) to exert long-term effects in aquatic animals.Occupational exposure may pose greater risks due to skin and inhalation exposures, resulting in much higher transient blood acetochlor concentrations (μmol·L−1).Previous works have identified liver as the most susceptible toxicological target for acetochlor, and cytosolic calcium is known to play a vital role in multiple hepatocyte functions.Therefore the present work aims to examine acetochlor effect on calcium oscillations induced by adrenergic receptor activation in freshly isolated rat hepatocytes. It was found that acetochlor at lower concentrations (1, 10 μmol·L−1) added simultaneously with phenylepinephrine (PE) had no effect on PE-induced calcium oscillations, but inhibited reversibly calcium oscillations at higher doses (50, 100, 200 μmol·L−1) of acetochlor in selected hepatocytes.Brief prior acetochlor exposure (1, 10, 100 μmol·L−1), however, had no apparent effect on either basal calcium or subsequent PE-induced calcium oscillations.Immunocytochemistry identified non-uniform α1 adrenergic receptor expression among isolated hepatocytes.Immunohistochemistry of liver slices revealed a distinct pattern of α1 adrenergic receptor density in liver lobules: a gradual low-to-high receptor density gradient from pericentral to periportal regions.This receptor density gradient is likely related to acetochlor inhibition in selected hepatocytes.Taken together it is concluded that acetochlor at blood concentrations attainable during acute skin exposure or acetochlor poisoning may exert transient inhibitory effects on α1 receptor signaling in the liver.
Quantifying regional carbon inequality and policy implications under the “Belt and Road” Initiative
LIN Zekun, MENG Fanxin, WANG Dongfang, SUN Yutong, HU Yuanchao, LIU Gengyuan
2023, 59(1): 56-63. doi:10.12202/j.0476-0301.2022167
Abstract(151) HTML(33) PDF (871KB)(41)
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In the context of global trade, quantitative analysis of carbon inequality in the “Belt and Road” region, and clarification of internal mechanism of uneven distribution of embodied carbon emissions and economic benefits in the “Belt and Road” region lay the scientific foundation for implementation of green “Belt and Road” Initiative.Global Trade Analysis Project (GTAP) database was used to build an environmentally extended multi-regional input-output (MRIO) model.This MRIO model covers a total of 102 countries and regions in the “Belt and Road” region, divided into 9 areas according to location.Carbon emissions were calculated from the perspective of production and consumption, traces spatial transfer patterns of embodied carbon emissions and added value.Index of carbon inequality in bilateral trade and comprehensive index of carbon inequality in the global trade network were built, to comprehensively quantify and analyze the phenomenon of carbon inequality.In 2014, carbon emissions from production and consumption in the “Belt and Road” region accounted for 65.29% and 60.54% of total global carbon emissions (25966.23 Mt), respectively.Value added from production and consumption in the region accounted for 40.87% and 40.10% of total global value added (66971.427 billion US dollars), respectively.In Global trade, the “Belt and Road” region bore 1234.25 Mt of net carbon emission transfer from non “Belt and Road” region, and obtained 515.483 billion US dollars of net economic benefits from non the “Belt and Road” region.“Belt and Road” Middle East region, was found to be the only net importer of embodied carbon emissions: a transfer of 152.18 Mt of carbon emissions to “Belt and Road” region, and a net economic benefits of 280.136 billion US dollars in Global trade.China was the largest net exporter of embodied carbon emissions, bearing 903.98 Mt of net carbon emissions, 31.30% was from the “Belt and Road” region.China bore a net economic loss of 34.912 billion US dollars in Global trade.Carbon inequality index between China and “Belt and Road” Middle East region was the largest, reaching 1.75.China was in a disadvantaged position for carbon inequality in bilateral trade, mainly due to serious mismatch of embodied carbon emissions and value added in the bilateral trade between heavy industry, construction sector and “Belt and Road” Middle East region. Comprehensive index of carbon inequality in the global trade network of “Belt and Road” Middle East region was 2.53.Agriculture, construction, and service industries in the region were net importers of embodied carbon emissions, while the heavy industry sector obtained a large amount of net economic benefits.“Belt and Road” region was generally at a disadvantage in the global trade carbon inequality.Comprehensive indexes of carbon inequality in global trade network of China, “Belt and Road” South Asia region and “Belt and Road” Europe region were −2.60, −2.16 and −2.22 respectively, being victims of carbon inequality in global trade.This work provides the scientific basis for implementation of green “Belt and Road” Initiative under Global trade and realization of coordinated development of the “Belt and Road” regional carbon governance and economy.
Water survey, monitoring and assessment system in America and implications for China
LIU Hongcang, BAO Kangni, ZHU Wenbin
2023, 59(1): 64-71. doi:10.12202/j.0476-0301.2022108
Abstract(0) HTML(0) PDF (545KB)(0)
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Systematic reviews of water survey, monitoring and assessment system in developed countries provide useful reference for construction of natural resources survey and monitoring system in China.Historical developments in water survey, monitoring and assessment in America are reviewed by literature search.The current status of water survey, monitoring and assessment in America was outlined by focusing on monitoring technology, organization, survey objectives, survey contents and assessment methods.Progress in water survey, future-plan of water survey in America are summarized.Current problems in water survey and assessment in Chinas are compared and analyzed.Lessons could be learned in four areas: data sharing, uncertainty analysis, development and application of hydrological models, and promotion of remote sensing technology.
Simulation and application of hydrological frequency distribution with insufficient data
FENG Jinghan, QIAN Longxia, TANG Jiashan, WANG Hongrui
2023, 59(1): 72-84. doi:10.12202/j.0476-0301.2022264
Abstract(44) HTML(21) PDF (2771KB)(24)
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Traditional hydrological frequency analysis often requires large numbers of samples to ensure good fitting of distribution, but few hydrological data records are available for some stations in China.This paper studies the small sample algorithm.The Jackknife method, Bootstrap method and traditional parameter estimation methods in hydrological frequency analysis are combined to obtain new parameter estimates to enhance fitting effect of traditional hydrological frequency distribution.The Jinghe River basin is taken as an example to verify advantages and disadvantages of this algorithm.Annual maximum daily precipitation data at 8 stations are selected as original sample.Small sample algorithm is used to re-sample the samples with different sample sizes multiple times, and the resampled samples are fitted with the distribution.Parameter estimation of small sample algorithm is obtained after parameter optimization.Kolmogorov-Smirnov (K-S) test and RMSE test are used to verify improvement of small sample algorithm upon traditional parameter estimation method.The fitting effect of small sample algorithm is markedly better than traditional algorithm in cases of small sample size.The fitting effect of Bootstrap for small samples is almost the same as traditional parameter estimation method using larger sample sizes.When the sample size at some stations is small, the distribution obtained by the traditional method cannot pass the K-S test, but the small sample algorithm can get better results.
Hydrological simulation and runoff components analysis in the high cold alpine region: case study in the upper reaches of the Parlung Zangbo watershed of the Yarlung Zangbo River basin
BAN Chunguang, XU Zongxue, ZUO Depeng, LI Peng, WANG Jing, DA Waciren
2023, 59(1): 85-93. doi:10.12202/j.0476-0301.2022240
Abstract(0) HTML(0) PDF (984KB)(0)
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Runoff components in high cold alpine region were investigated in the Parlung Zangbo basin.The multi-objective calibration methods such as monthly flow, remote sensing snow area data and measured glacier runoff data were used to calibrate model instead of only using streamflow data.Both hydrological simulation and runoff analysis were carried out based on SPHY (Spatial Processes in Hydrology) hydrological model, to improve overall simulation quality.Nash–Sutcliffe coefficient of efficiency in calibration and validation periods were found to be 0.95 and 0.94, respectively.The model had a good applicability.Rainfall runoff, snow runoff, glacier runoff and base flow were the sources of runoff, accounting for 10%, 25%, 45% and 20% of the total, respectively.Glacier melt water and snow melt water were the most important sources.On a monthly scale, glacier runoff accounted for the largest proportion from July to August, snowmelt runoff accounted for the largest proportion from April to June, and rainfall runoff accounted for the smallest proportion.Glacier runoff accounted for the highest proportion, which could provide more water resources to ensure social and economic development in the short term. In the long term, glacier runoff would gradually decrease, resulting in water shortage.Therefore, the local government needs to improve strategies to deal with potential risks of runoff changes.
Typhoon disaster risk assessment in Guangdong province by regional disaster system theory:case of “Mangkhut”
BAO Wenxuan, GONG Adu, XU Can, LI Boyi, HUANG Zhiqing
2023, 59(1): 94-103. doi:10.12202/j.0476-0301.2021263
Abstract(260) HTML(88) PDF (5176KB)(49)
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The main purpose of this research is to construct a typhoon disaster risk assessment model suitable for Guangdong province, so as to provide targeted reference advice on disaster relief and emergency decision-making after the occurrence of typhoons.Under the guidance of regional disaster system theory, this paper comprehensively constructs a new evaluation indicators system from three aspects: the fatalness of disaster-inducing factors, sensitivity of disaster-formative environment, vulnerability of disaster-bearing body and constructs the Guangdong province typhoon disaster risk assessment model based on the weighted comprehensive evaluation method, the analytic hierarchy process and the natural breaks point classification method.And illustrated by the case of the super typhoon No. 22 in 2018 “Mangkhut” to conduct a typhoon disaster risk assessment in Guangdong province, and finally a comprehensive risk zoning map of 1 km×1 km spatial units and the results of evaluation and analysis will be formed. The result shows that: 1) The medium and high-risk areas evaluated by the model for the “Mangkhut” typhoon disaster in Guangdong province are consistent with the disaster report and have high reliability; 2) The fatalness of disaster-inducing factors of the “Mangkhut” typhoon disaster in Guangdong province are high in the central-eastern coastal and central-western regions, and gradually decrease to the surrounding areas; 3) The areas with high sensitivity of disaster-formative environment in Guangdong province typhoon disaster are concentrated in the Pearl River Delta area and the Chaoshan area in eastern Guangdong.These areas are the flat terrain, dense river network and low vegetation coverage; 4) The areas with high vulnerability of disaster-bearing body in Guangdong province typhoon disaster are concentrated in the Pearl River Delta area, the Chaoshan area in eastern Guangdong and the Maozhan area in western Guangdong.These areas are densely populated, economically developed, numerous arable land and highly urbanized; 5) The comprehensive risk of “Mangkhut” typhoon disaster in Guangdong province are high in the central-eastern coastal, central-western regions and gradually decrease to the surrounding areas.The highly risk areas mainly include Yangjiang city, Jiangmen city, Zhuhai city, Shenzhen city, Huizhou city, Shanwei city, etc.
Radiometric correction of BNU-1 wide-swath imagery
ZHANG Zhuoyu, ZHANG Ying
2023, 59(1): 104-112. doi:10.12202/j.0476-0301.2021209
Abstract(97) HTML(50) PDF (3609KB)(19)
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BNU-1, the first civil polar optical micro-sat developed by Chinese scientists, is equipped with a medium and high-resolution multi-spectral wide-swath camera, and takes into account both revisit cycle and resolution.BNU-1 is of great significance for the study of climate and environment change and monitoring in polar regions, at high coverage and medium resolution.However, the band noise of level 0 data masks the ground feature of image and does not reflect the real radiation characteristics of ground features, seriously affecting data application.Therefore, in this paper a method is proposed to remove the strip based on statistical principle for wide-swath image.The algorithm uses the dark noise extraction method corresponding to the image of 0° solar altitude angle and the uniform scene mask method to extract offset and gain values of each detector respectively, and realizes the strip removal.Experimental data indicate that compared to original data, this algorithm robustly removes band noise, restores real surface radiation information, and gives full play to the application value of multispectral data of BNU-1.
Land use change and ecological security in Aksu
MA Wei, ZHANG Wenxin, WANG Hongrui, JIN Feng, DU Bin, WU Fengqi
2023, 59(1): 113-124. doi:10.12202/j.0476-0301.2021317
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Abstract:
To explore ecological security response to multi-scenario land use changes in arid areas will help to promote scientific land development and utilization and to build ecological security systems.The CA-MCE-Markov model was applied to design and simulate land use changes in natural development, economic development priority and internal enhancement scenarios in Aksu in 2030.PSR model was used to evaluate land ecological security levels quantitatively.In terms of area change, simulation indicated that cultivated land will decrease by 774 square kilometers, urban and rural construction land will increase by 100 square kilometers in an internal enhancement scenario, to achieve intensive development.Natural development and economic development priority scenarios will increase cultivated land by 3436 km2, urban and rural construction land by 386 km2.In terms of spatial change, inversion positions of cultivated land, forest land and water area in natural development scenario are inconsistent with reality, layout of urban and rural construction land in economic development priority scenario is rough, layout of urban and rural construction land in internal enhancement scenario is reasonable.If development status continues over the years, level of ecological security will continue to decrease. If economic development is given priority, safety pressure and bearing capacity response are still serious problems.In contrast, ecological security level of internal enhancement scenario will be greatly improved, which is the optimal simulation scheme and high ecological security.By evaluating multi-scenario land use changes, we provide measures and methods to solve actual conflicts, seek sustainable development, and improve ecological environment.
Comparison of Smartphone App and digital hemispherical photography for Estimating Leaf Area Index
HONG Chuqiao, QU Yonghua
2023, 59(1): 125-135. doi:10.12202/j.0476-0301.2021232
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Abstract:
Leaf area index (LAI) is a structural parameter that describes distribution characteristics of vegetation leaves in canopy.LAI can affect redistribution of solar radiation, photosynthesis capacity of vegetation and microclimate in vegetation growth environment. Therefore, obtaining LAI in ground measurements is of great significance to understand growth status of vegetation.Digital hemispherical photography (DHP) has been widely adopted due to its simplicity and low cost.In recent years, smartphone-based LAI measurement methods have been extensively used.However, in-depth comparison and verification between smartphone and DHP methods have not been done.Performance of smartphone for measuring LAI needs to be validated and its potential to replace DHP needs to be explored.In this paper we measured coniferous-broadleaved mixed forest, broadleaved forest and crop by self-developed smartphone APP (LAISmart).These DHP measurements were used as reference for comparative studies.LAI values derived from LAISmart were found highly consistent with DHP (R2=0.95, RMSE=0.68), but performance of LAISmart was affected by density of vegetation leaves.When LAI was > 3.9 , LAISmart significantly underestimated measurements of DHP.Auto-exposure mode of smartphone imaging sensor was an important factor for LAISmart underestimations in LAI in high-value areas.When exposure of LAISmart images in LAI high-value areas are reduced, deviation between LAISmart and DHP was reduced, accuracy of LAISmart was improved by 49%.Narrow sensor field of view (FOV) of LAISmart has little effect on measurement results.These data suggest that LAISmart, with higher efficiency and lower costs, can be an alternative to DHP.
Dynamic changes and influencing factors of farmland pattern in Yarlung Zangbo River basin from 2000 to 2015
ZHANG Tianyuan, SHEN Shi, CHENG Changxiu, YE Sijing
2023, 59(1): 136-146. doi:10.12202/j.0476-0301.2022126
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Abstract:
The Yarlung Zangbo River basin (YZRB) is a major agricultural area on the Tibetan Plateau.Analysis of dynamic changes of YZRB farmland pattern and influencing factors is of great significance to ensure self-sufficiency of grain and stable development of social environment in Tibet.The 30 m land use data were used in geodetector and geographically weighted logistic regression to analyze farmland requisition-compensation dynamic and influencing factors in YZRB from 2000 to 2015.Farmland requisition was found to have mainly occurred in peri-urban area of Lhasa (60.42%), Nyingchi (16.21%), and Lhoka (13.01%), mostly have transformed into waters and urban areas.Farmland compensation mainly distributed in Xigaze (55.81%), Nyingchi (23.26%), and Lhasa (19.61%), mostly from forest and grassland.Economic development, transportation infrastructure, and administrative factors mainly influenced farmland requisition.Investment, administrative and elevation factors mainly influenced farmland compensation.Spatial stratified heterogeneity was apparent in driving factors of farmland dynamics.Labor force transfer, tourism development, and backward farming concepts were main farmland development problems faced by Xigaze, Lhasa, and Nyingchi, respectively.This study elucidates farmland requisition-compensation dynamic and could guide high-quality coordinated development of agriculture in the Tibetan Plateau.The reserve farmland in the suburbs of Lhasa and Nyingchi should be protected, while agricultural policy tendencies such as capital and technical training should be given in Xigaze, to realize differential protection and management of farmland in the YZRB.
Spatio-temporal changes in grassland degree in the Qinghai-Tibet Plateau from 2000 to 2015
LI Xueying, XU Yawei, WANG Zheng, SU Yun
2023, 59(1): 147-155. doi:10.12202/j.0476-0301.2022127
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Abstract:
The study of spatiotemporal variation of grasslands shed light on understanding the causes and effects of transition of grassland quality.This article aims to provide basic data on the cause and effects as well as the mechanisms of grassland degradation.The grassland degree index (GDI) calculated from weighted index of NPP and NDVI was applied to represent the quality and coverage of grassland.Transition matrix and the slope index of GDI demonstrated the spatiotemporal pattern.From 2000 to 2015, total area of Class Ⅰ (high-quality grass) and Class Ⅳ (poor quality grass) remained unchanged.Some 28.11% of class Ⅰ grassland changed into class Ⅱ.The proportion of class Ⅱ that transformed into class Ⅰ and class Ⅲ were 18.19% and 21.53%, respectively.About one third (28.54%) of class Ⅲ transformed into class Ⅳ.From 2000 to 2015, grassland has undergone a trend of degradation-restoration-degradation pattern.The map of slope demonstrated that grassland conditions in the north has improved, while in the south has deteriorated, several local areas had undergone severe degradation in particular.
Community characteristics, distribution and environment interpretation ofCupressus giganteaalong Yarlung Zangbo River in Tibet
YANG Ganggang, HAO Haixia, YUE Yanpeng, ZHOU Jihua, LAI Liming, ZHENG Yuanrun
2023, 59(1): 156-162. doi:10.12202/j.0476-0301.2022125
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Abstract:
It is important to understand the dynamics of plant community and its response to environmental change.Cupressus giganteais a national-level protected plant distributed from Milin county to Lang county along the Yarlung Zangbo River.Two-way indicator species analysis (TWINSPAN) clustering and Canonical Correspondence Analysis (CCA) ordination were used to study plant community distribution and its relationship with environment.Plant communities inC. giganteadistribution area showed a simple structure and could be divided intoC. giganteacommunity,C. gigantea-Artemisiasacrorumcommunity andPinus densatacommunity.Canonical Correspondence Analysis showed that the first axis was significantly related to elevation and soil water content, soil bulk density and soil texture, mainly reflecting influence of moisture and thermal conditions, and soil properties.The second axis was related to latitude, slope aspect, soil phosphorus content, annual precipitation, soil total potassium and soil nitrogen-phosphorus ratio, mainly reflecting changes in soil nutrients, precipitation and light conditions.Two determining factors for community distribution were: difference in moisture and thermal conditions induced by changes in elevation and slope aspect, difference in soil physical and chemical properties.The main distribution altitudinal ranges ofC. giganteacommunity,C. gigantea-Artemisiasacrorumcommunity andPinus densatacommunity were 3000-3400, >3400-3500 and >3500-3600 m, respectively.These data are important to understand environmental characteristics of plant communities in the distribution area ofC. gigantea, and will help to protect plant resources ofC. giganteamore effectively.
Spatial-temporal changes in urbanization level and influencing factors on the Tibetan Plateau: perspectives from long-term time series nighttime light data
WANG Yihang, LÜ Caifeng, PAN Xinhao, LIU Zhifeng
2023, 59(1): 163-174. doi:10.12202/j.0476-0301.2022021
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Abstract:
It is of great theoretical and practical significance to accurately quantify changes in urbanization on the Tibetan Plateau, to understand economic, social and ecological responses in the region.Due to imperfect social and economic statistical data of the Tibetan Plateau, relevant research has not been done on urbanization level dynamics.The recently released long-term nighttime light data provides an opportunity to study changes in urbanization level on the Tibetan Plateau.The dynamics of urbanization level on the Tibetan Plateau was quantified from such data from 1992-2018.Changes have been analyzed on multiple scales: provincial-level administrative regions, prefecture-level administrative regions, county-level administrative regions, as well as watersheds.Spatial agglomeration characteristics and influencing factors in different time periods were analyzed.The overall urbanization level on the Tibetan Plateau showed an accelerated growth trend from 1992-2018, significant spatial differences were found.From 1992-2018, CNLI increased from 1.03×10−4to 4.46×10−3, with an average annual increase of 1.67×10−4.The area and number of high-level urbanization clusters increased significantly.Three areas with high level of urbanization have formed around Xining, Lhasa, and southeast edge of the region.The urbanization levels are mainly affected by traffic and topography, influence of traffic factors is constantly increasing.It is concluded that quantification of urbanization from long-term nighttime light data is effective and can be applied to other areas with imperfect statistical data.

Since 1956  Bimonthly

Supervisor:Ministry of Education of P.R.C.

Sponsors by:Beijing Normal University

Director:SONG Changqing

Chief Editor:BAO Jiguang

Email:jbnuns_sub@bnu.edu.cn

ISSN0476-0301

CN11-1991/N

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