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Table of Content

    20 September 2014, Volume 50 Issue 5
    Spatial Frequency Based Remote Sensing Radiative Response Modeling and Its Geometry Correlation Research
    ZHAO Shihu,TANG Xinming,YIN Dan,HAO Shengyong,DOU Xianhui,HU Yuan
    2014, 50(5):  895-903. 
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    Following the optical remote sensing imaging mechanism and combining image spatial spectrum, MTF (modulation transfer function) and SNR (signal noise ratio) models together organically, a novel spatial frequency based radiative respond modeling (SFRR) is presented which has definite physical meaning. SFRR has two breakthrough points, one is reducing the comprehensive radiative model’s dependence on the complicated earth object’s spectral and reflectance; the other is establishing the theory basis of radiative and geometric quality correlation modeling. In geometric positioning accuracy experiments, the ZY3 satellite’s forward and backward stereo images are used to produce multilevel MTF degrade and noised simulation images. By automatic registering the forward and backward images, the Root-Mean-Square error of matched points is computed to judge the correlation between SFRR and geometric positioning accuracy, which proves that SFRR model has good correlation with geometric quality. The research will be helpful for optical remote sensing system optimizing, remote sensing image processing and applying.
    Effects of Experimental Nitrogen Additions on Understory Species Diversity in Four Forests in China
    HU Junyu,ZHU Jianxiao,ZHOU Zhang,LI Peng,CUI Jun,TANG Zhiyao,FANG Jingyun
    2014, 50(5):  904-910. 
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    To investigate the effects of experimental nitrogen additions on the species diversity of the forest understory, the authors measured the plant diversity of the primary and the secondary tropical mountain rain forests, the subtropical evergreen broad-leaved forest, the temperate broad leaf-coniferous mixed forest and the cold temperate coniferous forest before and after N additions. Results showed that 1-year N addition significantly reduced the species richness in the primary and the secondary tropical mountain rain forests and the effects of N additions would be increased with the concentration of N additions (p < 0.05). Meanwhile, the high-concentration N addition also reduced the species richness, but low-concentration N addition increased the species richness in the temperate broad leaf-coniferous mixed forest. In addition, N additions increased species richness in the subtropical evergreen broad-leaved forest and the cold temperate coniferous forest (except for the high-concentration), but not significant. Moreover, the changes of Shannon-Wiener index responded to N additions have the similar trend with the change of species richness. The results suggested that nitrogen deposition changed biodiversity in the understory forests, but effects of N addition on biodiversity differ among the dfferent forests in China. Inconsistent with the general view, N addition reduced biodiversity in some forests but increased biodiversity in the others.
    Geochronology, Geochemistry and Geological Significance of the Permian Bimodal Volcanic Rocks in Xi Ujimqin Banner, Inner Mongolia
    CHEN Yan,ZHANG Zhicheng,LI Ke,LUO Zhiwen,TANG Wenhao,LI Qiugen
    2014, 50(5):  843-858. 
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    In order to understand the Late Paleozoic tectonic setting of eastern part of Central Asian Orogenic Belt more deeply, the Permian volcanic rocks from Xi Ujimqin Banner, Inner Mongolia were selected to study their geochronology and geochemistry. The contents of major elements, the age, the contents of trace elements and REEs and the Sr-Nd isotopes of the volcanic rocks were measured by X-ray fluorescence spectrometry (XRF), SHRIMP zircon U-Pb, ICP-MS and ISOPROBE-T, respectively, and the results are as follows. The volcanic rocks consist of subordinate basaltic andesites and dominant rhyolites, with the SiO2 content ranges of 53.54%?54.71% and 72.61%?80.81%, respectively. The SHRIMP zircon U-Pb age of one rhyolite specimen is about 279 ± 4.3 Ma, indicating that the rhyolites erupted in Early Permian. The basaltic andesites are characterized by slightly enriched LREE, depleted HREE, slightly negative Eu, Nb, Ta and Sr anomalies, and high abundances of LILE and HFSE, with the (La/Yb)N ratios of 2.06 to 2.34. The mafic rocks may be inferred to generate from deep non-primitive mantle largely mixed by crustal source according to these features above. The rhyolites are characterized by slightly enriched LREE, depleted HREE, intensively negative Eu, Sr, P and Ti anomalies, slightly depleted Nb and Ta, and high abundances in K, Zr and Hf, with the (La/Yb)N ratios ranging from 1.70 to 3.81, relatively high positive εNd(t) values (+3.98?+5.62) and relatively young TDM (490?690 Ma). The felsic rocks show an A-type affinity and may be inferred to come from a juvenile crustal source. According to their geochemistry, regional geology and previous studies, these bimodal volcanic rocks were generated by intra-plate volcanism and formed in a post-collisional extensional setting.
    Evaluation of the Ahe Sandstone Tectonic Fractures in the Yinan-Tuzi Area, Kuqa Depression
    JU Wei,HOU Guiting,HUANG Shaoying,REN Kangxu
    2014, 50(5):  859-866. 
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    By the use of well logging data, the tectonic fracture porosity was calculated, the influence of tectonic fractures to Young’s modulus was quantitatively described with the theory that the development of tectonic fractures would decrease the value of Young’s modulus, and the “Fracture Evaluation Indicator ( f )” was first proposed to evaluate the levels of tectonic fracture development. The development evaluation of Ahe low porosity and low permeability sandstone fractures was carried out with the fracture evaluation indicator, and the evaluating results showed that the Well Yinan-2 areas and the glutenite with mudstone segment of Ahe formation are the most tectonic fracture developed places in the horizontal and vertical plane of Yinan-Tuzi areas respectively.
    An Improved Method of AVO Character Extraction for Anisotropic Medium Bounded by a Dipping Surface
    LI Xue
    2014, 50(5):  867-872. 
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    The author derives the relationship between incidence angle and offset in the model where the overlaying layer is homogeneous and isotropic medium while the under-cladding layer is anisotropic. Based on the reflection coefficient expressions in Horizontal Transversely Isotropic medium (HTI medium) proposed by Ruger, and inverses the elastic parameters of layers. By comparing the results with other previous methods, it verifies the correctness of the new method and the superiority of the algorithm.
    Complex Structural Properties of Urban Taxi Passenger Flow Network
    LIU Yuefeng,SI Ruochen,KANG Wei
    2014, 50(5):  873-879. 
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    By analyzing floating taxi trajectory data, and using complex network theories, the complex structural (including topological structural, weight structural and spatial structural) properties of urban taxi passenger flow network is researched. The results indicate that the distances of taxi passenger flow obey a log-normal distribution. Distributions of degree, weight strength and distance strength of nodes indicate power-law decay with a “cut-off”. Weight distribution of edges also fits a power-law distribution quite well. There are strong power-law correlations between degree and both weight strength and distance strength. The assortative mixing of weight strength of nodes shows a slight positive correlation. These results indicate the relationships of topological, weight and spatial structural properties of taxi passenger flow network, and will be beneficial for revealing the interplaying mechanism and principles among urban spatial, functional and population travel characteristics.
    Role of Distance Constraint in the Structure of Taxi Passenger Flow Network
    JIAO Long,LIU Yuefeng,SI Ruochen
    2014, 50(5):  880-886. 
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    By analyzing the floating taxi trajectory data, the existence of distance constraint in taxi passenger flow is found. Flow evolution model considering distance constraint is proposed and networks for different constraint parameters are simulated and compared. The results indicate that the distance constraint contributes to a “cut-off” of degree distribution, weight strength distribution, distance strength distribution, and a shorter distance constraint leads a more pronounced “cut-off”. With the decrease of constrained distance, the decaying rate of edge weight distribution slows down. Both degree-weight strength correlation and degree-distance strength correlation are power-law relations, and the exponents increase with the decrease of constrained distance. As the constrained distance decrease, the assortative mixing for weight strength of nodes changes from negligible negative correlation to positive correlation. These results help to reveal the effecting principles of the distance constraint of population travels on the structure of taxi passenger flow network.
    Factor Decomposition of Grain Production at County Level in Henan Based on LMDI
    LIU Yu,PAN Yuchun,REN Xuhong,TANG Xiumei
    2014, 50(5):  887-894. 
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    The LMDI technique and decomposition method are used to study the contribution of factors to grain production change based on grain production calculating model in Henan from 1980 to 2010. The growth of grain production is decomposed into four effects, including cultivated land area, multiple-cropping index, grain farming index and grain yield per hectare, and then accumulated effect of each factor is explored. Firstly, grain production increases by 54.371 million ton from 1980 to 2010. It is estimated that the accumulated contribution values of cultivated land area, multiple-cropping index, grain farming index and grain yield per hectare at province level are -1.754 million, 11.657 million, -5.734 million and 28.716 million ton, respectively. Grain yield per hectare is the dominant contributor to total grain increment, and multiple-cropping index is second. Secondly, at prefecture-city level, the effect of grain yield per hectare and multiple-cropping index is positive, while the other two factors in most of prefecture cities are negative. Thirdly, the pattern “high in the eastern while low in the western” of grain production at county level in Henan is very evident, and there are obvious differences among accumulated effects of the four factors. Overall, multiple-cropping index and grain yield per hectare result in remarkable grain increment in eastern Henan. Aiming at steady and continuous increase in grain production, some work such as cultivated land protection mechanism to increase grain sowing area, investment policy of agricultural infrastructure and optimization of agricultural inputs to improve grain yield per hectare should be enhanced.
    Effects of Nutrient Additions on the Arbuscular Mycorrhizal Fungal Colonization in the Alpine Meadow on the Tibetan Plateau
    HUANG Yuanyuan,OLBRECHT Luise,YANG Xiaoxia,HE Jinsheng
    2014, 50(5):  911-918. 
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    An experiment was conducted to investigate the effects of nutrient additions on the arbuscular mycorrhizal fungi (AMF) colonization in the alpine meadow at Haibei field station in China. Treatments of the experiment were control, N addition (10 gN/(m2•a)), P addition (5 gP/(m2•a)), and K addition (10 gK/(m2•a)), each with six replicates. With ink-vinegar staining method, mycorrhizal colonization of roots of the meadow plant community was quantified. Results showed that N addition significantly reduced total mycorrhizal root length colonization by 27%, but had no effect on the arbuscular and vesicular colonization. There was a trend towards reducing AMF colonization by the P addition, but not significantly. K addition did not influence the AMF colonization. The results indicate that there is different influence on the AMF in the alpine meadow with different fertilizer application, which may influence the structure and function of the ecosystem such as the change of species composition. So it is necessary to take the AMF into consideration when evaluating the effects of nutrient additions.
    Estimating Grazing of Inner Mongolia Grassland by Using Remote Sensing Method
    XIE Rui,WU Xiuqin
    2014, 50(5):  919-924. 
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    Based on Inner Mongolia grassland as the study area, using the MODIS NDVI data, combined with field experiment and statistical yearbook, grazing capacity estimation model is established, and has carried on the estimate for 2012 grazing intensity. The results show that grassland grazing capacity and the difference between two period of NDVI was significantly positive correlation. Through regression analysis, grazing capacity estimation model is Y = 4.203 ( Xi - Xj ) + 956.572. Grazing intensity of various types of grassland in Inner Mongolia evidently decrease gradually from west to east. The grazing intensity is meadow steppe
    Spatial-Temporal Collocation of Rural Residential Land Consolidation Based on Interaction of Urgency and Suitability Degree
    QU Yanbo,JIA Sha,SHANG Ran,JIANG Guanghui,GAO Yu
    2014, 50(5):  925-934. 
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    Firstly, according to the spatial-temporal characteristics of rural residential land consolidation, in order to guide the multiple target of rural residential land consolidation, the influence factors of different goals are classified as two aspects, which are urgency and suitability of rural residential land consolidation. Secondly, with the comprehensive evaluation of rural residential land consolidation urgency-suitability degree and construction of exclusive matrix combining method, the authors list the different target scheduling of rural residential land consolidation and establish the spatial organization and allocation pattern under the guidance of multiple target. The case study in Pinggu district in Beijing show that time urgency of rural residential land consolidation is divided into four grades, high, moderate, low and no urgency, and the proportions of village number are 12.73%, 28.36%, 24.73% and 34.18% accordingly. Characteristics of special distribution is urgency level from high to low layer structure. Space suitability of rural residential land consolidation is divided into four grades, high, moderate, low and no suitability, and the proportions of village number are 11.27%, 33.09%, 36.73% and 18.91% accordingly. There is obvious group layer structure in special distribution of village. Combining with urgency and suitability level results, the spatial-temporal collocation pattern for rural residential consolidation land is formatted, which are the priority areas in the near future, the key areas in the medium term, the suitable areas in the long term and limiting consolidate. The goal orientation and safeguard measures in different areas of rural residential land consolidation has also been put forward.
    Evolutionary Game Analysis on Environmental Cooperation of Rural Households
    LI Lili,HU Xuan,YANG Shunshun,LUAN Shengji
    2014, 50(5):  935-941. 
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    The process of institutional change that environmental cooperative state of rural households changing into environmental non-cooperative state of rural households comes with a cost. In the process, there is an environmental game played repeatedly by rural households. Here evolutionary game theory was used to analyze the evolutionary process and the equilibrium of the environmental game system. A replicator equation was developed to analyze evolutionary stability of the system. Then the source of stochastic disturbance which the process has suffered is analyzed. On this basis, stochastic evolutionary game model was developed to analyze stochastic evolutionary dynamics and stochastic evolutionary stability. Results show that whether environmental cooperation will become the result of the evolution depends on 1) taking into account direct costs and benefits along with losses caused by the positive externalities, environmental behavior is still profitable or not; 2) conventions of the game’s process. To promote current system changing to the system of rural households’ environmental cooperation, one way is to take selective incentives to increase payoffs of rural households who will take environmental behaviors, and those who provide selective incentives measures will commitment the main costs of institutional change; and another way is to establish action-repeating mechanism, making environmental cooperation become the only convention in recent past, and those who provide action-repeating mechanism will commitment the main costs of institutional change.
    Sensitivity of Air Temperature to Land Cover Change in Eastern China during the Last 30 Years
    FENG Yao,LI Yan,ZHAO Xinyi,LIU Wenjun
    2014, 50(5):  942-950. 
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    Utilizing land cover change (LCC) information together with monthly average air temperature record of 295 meteorological stations densely-scattered in eastern China, sensitivity of regional air temperature of meteorological stations to LCC is explored from 1979 to 2010. Results reveal that area of grassland decreases dramatically with that of urban skyrocketing as well as obvious enlargement in forest area. The annual temperature trend ranges from -0.2 to 0.9℃/10a, averaged 0.38℃/10a, which differs among stations characterized by various land covers, indicating a decreasing trend from urban to cropland to grassland to forest to water. The impact of LCC on air temperature is collaboratively driven by land covers around stations. Though it is not exactly the only causative factor of regional warming, LCC does affect temperature variation profoundly.
    Evaluating City-Scale Net Anthropogenic Nitrogen Input (NANI) in Mainland China
    GAO Wei,GUO Huaicheng,HOU Xikang
    2014, 50(5):  951-959. 
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    Based on NANI calculator, statistic data and parameter from 358 cities of China (Hong Kong, Macao and Taiwan are not included) are applied to assess net anthropogenic nitrogen input (NANI) at China’s city scale. On average, NANI of Mainland China has reached to 45.15 Tg in 2010, and on a per area basis the value is 4716 kg/km2, which is 3 times than world average level. Nitrogen fertilizer input dominates NANI budget items, which accounts for 65.0% of the total, net food and feed input (21.4%), oxide N deposition (7.3%) and crop fixation (6.5%) follow. On geographical basis, NANI of the 358 cities has an obvious characteristic of regionalization, and high value areas appear in cropland and population concentrated places. Compared to province scale data, data on city scale is more effective to assist in discerning key regions, which is able to control more nitrogen input with smaller control area.
    Synthesis of a New Ionic Imprinted Polymer for the Adsorption of Uranium from (NH4)4[UO2(CO3)3] Solution
    ZHANG Hongjuan,CHEN Qingde,SHEN Xinghai
    2014, 50(5):  960-964. 
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    The ionic imprinted polymer (IIP) of uranyl ion (UO22+) was synthesized by the formation of binary complexes of UO22+ with 1,3-dioxo-1,3-diphenylpropan-2-yl methacrylate (DBM-MAA) as functional monomer followed by thermal copolymerization with ethylene glycol dimethacrylate (EGDMA) as cross-linking monomer in the presence of 2,2′-azobisisobutyronitrile (AIBN) as initiator and 1,4-dioxane as porogenic solvent. 50 mmol/L HCl solution was used to leach out UO22+ ions from the polymer. The IIP formed with 1:3 molar ratio of UO22+ to DBM-MAA showed better enrichment of uranyl ion from dilute aqueous solution than others and hence was chosen for detailed studies. The maximum adsorption capaci(NH4)4[UO2(CO3)3]sub>)3] solution was 9.4 mg U/g. The prepared IIP could selectively separate UO22+ from other metal ions, such as Li+, Na+, K+ and Rb+.
    Characteristic of the Cellulose Immobilized on Aminated SiO2
    ZHANG Boya,YANG Ting,HU Xia,ZHANG Jianbo
    2014, 50(5):  965-968. 
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    The immobilized cellulase was prepared by using aminated SiO2 with glutaraldehyde as crosslinking agent. The best immobilized reacting condition were glutaraldehyde concentration of 4% (v/v), crosslinking time for 60 minutes, cellulase dosage of 35 U/g and reaction time for 5 hours. The obtained immobilized cellulase displayed best enzyme activity. Compared with free cellulase, immobilized one had lower sensitivity to pH and temperature of reacting system and higher time stability and thermal stability. The immobilized cellulase had higer Ed, ΔH*, ΔS* and ΔG* to thermo inactivation reaction, which showed that the immobilization slowed down the inactivation velocity of cellulase and reduced the potentiality of inactivation reaction.
    Review of Risk Perception on Urban Air Pollution
    ZHU Kejun,XU Jianhua
    2014, 50(5):  969-978. 
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    The authors give a fairly thorough review on papers published in the recent twenty years related to public risk perception on urban air pollution. It summarized major factors affecting the public’s risk perception, including the characteristics of risk itself, peripheral environmental conditions, exposure routes, socio-demographic factors, and other individual characteristics. Specifically, the public’s perceived risk towards air pollution is weakly correlated with scientific air quality data released officially and in media. Instead, it is affected by their proximity to pollution sources, vegetation coverage, physical experiences, health status and anecdotes. Females, those with respiratory diseases, and those more educated are concerned more about air pollution and perceived a higher risk. Socioeconomic factors also affect the public’s perceived level of risks. Besides, this paper summarizes the quantitative and qualitative methods used to study perceived risk towards air pollution. Finally, future research directions are identified including how the public perceive the causal link between air pollution and health effects, effect of media and trust, and effect of risk perception on behavior.
    Review of the Forward Modeling and Inversion in Magnetotelluric Sounding Field
    CHEN Li,QIN Qiming,WANG Nan,BAI Yanbing,ZHAO Shanshan
    2014, 50(5):  979-984. 
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    Based on the theory of forward and inversion, forward and inversion methods are studied respectively. Firstly, the magnetotelluric forward and inversion problems are analyzed, and the development and classification of the forward and inversion methods are summarized. Secondly, the principle and procedure of the different methods are described briefly, and the advantages, limitations and enhancement methods are comparatively analyzed. Finally, the trend of the forward and inversion methods are pointed in the future. The three-dimensional forward modeling methods and the global optimization and nonlinear inversion methods will become the main development trend.
    Empirical Study on Members’ Motivations for Participating in Microblogs Community
    HU Lei,GAO Ying
    2014, 50(5):  797-804. 
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    The authors explore the impacts of members’ motivations for participating in microblogs community on their behaviors for participating, with the application of stepwise multiple regression analysis method. The study shows that the motivations of self-expression, informational value, entertainment value, and attentions for celebrities significantly impact members’ behaviors for participating in microblogs community. Furthermore, self-expression is the most important motivation that impacts the frequency and level of participation in microblogs community, and informational value is the most important motivation that impacts the time of participation. Finally, the conclusions can provide a basis for further studies of the impacting path of members’ motivations on their behaviors for participating in microblogs community and behaviors of participating under the context of social public events. At the practical level, the conclusions have some practical significances in operating and (or) managing microblogs community for microblogs service providers and relevant government departments.
    Research on Speech Synthesis for Large-Scale Corpora
    YU Yansuo,ZHU Fengyun,LI Xiangang,LIU Yi,WU Xihong
    2014, 50(5):  791-796. 
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    Aiming at roughly labeled corpora with several hundred hours of speech, a novel approach of constructing text-to-speech system is proposed. This approach realizes automatically cleaning and labeling of large-scale corpora by means of speech recognition, text alignment and syntactic parsing. Furthermore, in order to solve the problems of memory space expansion and time consumption for acoustic model training of large-scale corpora, a fast training method, which can ensure the accuracy of acoustic model, is realized through the optimization of conventional process of model training. Subjective evaluations show that the exploitation of large-scale corpora with rough transcription can achieve significant improvement at 0.5 MOS score in contrast with small-scale corpora with exact transcription.
    A Modified Method for Calibrating the Supersaturations in DMT Cloud Condensation Nuclei Counter
    MA Nan,ZHAO Chunsheng,DENG Zhaoze,TAO Jiangchuan,YU Renjie,CHEN Jing,BIAN Yuxuan
    2014, 50(5):  805-811. 
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    A modified method for calibrating the supersaturations in the chambers of DMT Cloud Condensation Nuclei Counter is introduced, which decreases the uncertainty in the results of the calibration. In the new method, the complete size-resolved activation ratio for ammonium sulfate is observed, and the activation critical diameter is yielded via fitting the size-resolved activation ratio with two Gauss error functions. With the new method, users can do the calibration periodically to guarantee high-quality observations.
    Microclimate Effects of Campus Green Space in Summer
    FENG Yueyi,LI Enjing,ZHANG Lixiao
    2014, 50(5):  812-818. 
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    Four representative types of green space including tree-shrub-herbage semi-natural mixture, tree-shrub-herbage artificial mixture, tree-herbage artificial mixture, and artificial lawn were selected in the campus of Peking University to study the improvement effects of green space on campus microclimate, especially on the human comfort. The air temperature and relative humidity were measured every one hour from 0:00 to 24:00 every day for continuously 32 days during July and August in 2012. The results indicate that all types of green space show significant cooling and humidification effects compared with the concrete floor in hot summer. Among these, the semi-natural forests perform a very important ecological regulatory function. During the observation period, all types of green space improve the human comfort degree to a certain extent, which are ranked in an order of tree-shrub-herbage semi-natural mixture > tree-herbage artificial mixture > tree-shrub-herbage artificial mixture > artificial lawn, but the improvement effect is not as obvious as their cooling and humidification effects. From the perspective of the different times of a day, the comfort improvement of the green space is more obvious early in the morning and late in the evening than that at any other time of a day. As a whole, some parts of the green space in the campus of Peking University don’t give full play to the improvement effects of the campus comfort according to the various functional requirements in summer, which deserves further attention in the campus green space construction.
    Convective Initiation Forecasting and Statistical Evaluation Based on Satellite Data
    LI Wusheng,WANG Hongqing,WANG Yu,WU Qiong
    2014, 50(5):  819-824. 
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    Eight forecast factors of convective initiation (CI) are calculated by using IR1, IR2 and WV TBB of MTSAT-1R satellite data based on target clouds identification. The critical values of forecast factors are proposed in Beijing-Tianjin region, and the 17 days test of convective initiation forecast in Beijing-Tianjin region during 2006 and 2007 is carried out. Results of the test show that this method of CI forecast can well forecast the CI occurs in the next one hour. The method of CI forecast results evaluation is proposed base on the atmospheric motion vectors, and a statistical analysis of the CI forecast results is conducted. Statistical results show that this CI forecast method has good TS score of 0.545, high POD of 0.654 and low FAR of 0.435.
    Assessment of the Location of One Background Monitoring Station to be Built with Particulate Matter Remote Sensing from Space
    LI Chengcai,ZHOU Yinliang,LI Ying,Alexis Kai-Hon LAU,HE Qianshan,YANG Fumo
    2014, 50(5):  825-834. 
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    The aerosol optical parameters derived from satellite remote sensing and the related surface PM10 mass concentration data in 2011?2012 over Suzhou and Wuxi Cities were used to assess the location selection of one background monitoring station to be built. The results showed that satellite remote sensing products with 10 km, 5 km and 2 km space average were all significantly correlated to the hourly PM10 concentration. Showing in the annual average regional distribution of satellite remote sensing results, the annual average PM10 mass concentration over the Xishan (the site to be built in Suzhou) will be significantly lower than those over the urban stations in the magnitude up to 14%. Statistical analysis based on an objective weather classification technique showed that the mean concentration of particulate matter over Xishan were lower than that of urban stations in the amplitude range of 7%?21% in various weather patterns. The smaller (7%?9%) concentration difference between the urban stations and the Xishan station could be found at two types of weather conditions, when there were a regional heavy pollution or a regional clean air quality, respectively.
    Estimation of Latent Heat Flux over Semiarid Areas for Clear Sky Days Using MODIS Data
    YE Jing,PENG Lichun,LIAO Qian,LI Zhiming
    2014, 50(5):  835-842. 
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    In order to study the distribution of latent heat flux in Northern China, a scheme, eliminating the need of ground meteorology data as input and only using remotely sensed information, is proposed to estimate latent heat flux over semiarid areas for clear sky days. In this scheme, latent heat flux is calculated based on surface energy balance: net radiation is estimated using an improved parameterization; soil heat flux is calculated through a regression equation; evaporative ratio is obtained by S-SEBI model. Based on land and atmospheric data products available from moderate resolution imaging spectroradiometer (MODIS), this scheme is validated by clear sky datasets at the degraded grassland site and the farmland site during June to November in 2003, 2004 and 2005. The results indicate that the proposed scheme can effectively calculate the latent heat flux. The root mean square error (RMSE) for the estimated latent heat flux in grassland and farmland are 60.4 and 64.6 W/m2 respectively, and the mean error (ME) are 18.6 and 32.4 W/m2 respectively.