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Ratio of photosynthetically active radiation to global solar radiation above forest canopy in complex terrain: measurements and analyses based on Qingyuan Ker Towers

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Ecological Processes 2024年第2期13卷 204-217页

作者： Shuangtian Li Qiaoling Yan Tian Gao Xingchang Wang Qingwei Wang Fengyuan Yu Deliang Lu Huaqi Liu Jinxin Zhang Jiaojun Zhu CAS Key Laboratory of Forest Ecology and Silviculture Institute of Applied Ecology Chinese Academy of Sciences Qingyuan Forest CERN National Observation and Research Station Chinese Academy of Sciences CAS-CSI Joint Laboratory of Research and Development for Monitoring Forest Fluxes of Trace Gases and Isotope Elements Institute of Applied Ecology Chinese Academy of Sciences (CAS) University of Chinese Academy of Sciences Center for Ecological Research Northeast Forestry University

Background Understanding of the ratio of photosynthetic photon flux density（Qp） to global solar radiation（Rs）(Qp/Rs) is crucial for applying Rsto ecology-related *** studies reported Qp/Rsand its variations based on measurements from a single observatory tower,instead of multi-site-based measurements over complex *** may neglect spatial heterogeneity in the terrain,creating a gap in an understanding of how terrain affects Qp/Rsand how this effect interacts with meteorological *** Here the Qingyuan Ker Towers（three towers in a valley with different terrains:T1,T2,and T3） were utilized to measure Qpand Rsover mountainous forests of Northeast *** airborne LiDAR system was used to generate a digital elevation model,and sky view factor of sectors（SVFs） divided from the field of view of tower's pyranometer was calculated as a topographic factor to explain the variations of Qp/*** The results identified significant differences in Qp/Rsof the three towers at both daily and half-hour scales,with larger differences on clear days than on overcast ***/Rswas positively correlated with SVFsof T1 and T3,while this correlation was negative with that of *** effect of SVFson Qp/Rsinteracted with clearness index,water vapor pressure and solar zenith *** forest-based importance assessment demonstrated that explanation（R2） on Qp/Rswas improved when SVFswas included in the predictor variable set,indicating that incorporating terrain effects enhances the prediction accuracy of Qp/*** improvement in the R2values was more pronounced on clear days than on overcast days,suggesting that the effect of terrain on Qp/Rsdepended on sky *** All findings suggested that Qp/Rsis affected by terrain,and integrating terrain information into existing Qp/Rsmodels is a feasible solution to improve Qp/Rsestimates in mountainous areas.

关键词： Photosynthetic photon flux density Clearness index Water vapor pressure Solar zenith angle Terrain sky view factor

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An efficient method of evaluating large scale urban residential skylight environment and an empirical study of Beijing main area

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Building Simulation 2021年第4期14卷 871-883页

作者： Taofang Yu Hongzhong Chen Ziwei Li Qiushi He Borong Lin Department of Urban Planning School of ArchitectureTsinghua UniversityBeijing100084China Department of Building Science School of ArchitectureTsinghua UniversityBeijing100084China College of Architecture&Urban Planning Beijing University of TechnologyBeijing100124China

A good skylight environment in urban residential areas is an important component of a healthy city,and has always been highly *** the rapid development of new-type urbanization,the density of buildings continues to increase,and megacities have entered the stage of stock *** effective method for evaluating the skylight environment of large-scale urban residential areas is urgently ***,there is still a lack of empirical research methods and cases of large-scale residential skylight *** this regard,this article takes the megacity Beijing as the research object,and proposes an efficient analysis method of residential skylight environment that integrates multiple real-world data at city *** terms of data,it collects and integrates 3D data of urban-scale building space and residential boundary data;in terms of algorithm,sky view factor(SVF)is used as the evaluation index of residential skylight environment,and an efficient analysis method of urban-scale skylight environment based on cloud parallel simulation is *** analysis,it is found that:(1)the average SVF value of Beijing residential area is 61%,which means that its skylight quality is in general level;(2)the skylight environment of Beijing residential area is distributed in a circle,and there are 4 types of skylight environment quality residential areas;(3)The skylight environment of Beijing residential area is relatively weakly related to the distance from the residential area to the city center and the average height of the residential buildings,and is closely related to the plot volume ratio,the residential building density and the shading from surrounding *** highlight of this study lies in the empirical research on the skylight environment of mega-city residential areas that incorporates multiple real data for the first time,which can promote the study of skylight environment on a city scale and provide a reference for the updating of Beijin

关键词： urban skylight environment sky view factor Open Street Map Buildings Beijing residential areas

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Geohazard Recognition and Inventory Mapping Using Airborne LiDAR Data in Complex Mountainous Areas

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Journal of Earth Science 2021年第5期32卷 1079-1091页

作者： Chen Guo Qiang Xu Xiujun Dong Weile Li Kuanyao Zhao Huiyan Lu Yuanzhen Ju State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China

Geohazard recognition and inventory mapping are absolutely the keys to the establishment of reliable susceptibility and hazard maps. However, it has been challenging to implement geohazards recognition and inventory mapping in mountainous areas with complex topography and vegetation cover. Progress in the light detection and ranging(Li DAR) technology provides a new possibility for geohazard recognition in such areas. Specifically, this study aims to evaluate the performances of the Li DAR technology in recognizing geohazard in the mountainous areas of Southwest China through visually analyzing airborne Li DAR DEM derivatives. Quasi-3 D relief image maps are generated based on the sky-view factor(SVF), which makes it feasible to interpret precisely the features of geohazard. A total of 146 geohazards are remotely mapped in the entire 135 km^(2) study area in Danba County, Southwest China, and classified as landslide, rock fall, debris flow based on morphologic characteristics interpreted from SVF visualization maps. Field validation indicate the success rate of Li DAR-derived DEM in recognition and mapping geohazard with higher precision and accuracy. These mapped geohazards lie along both sides of the river, and their spatial distributions are related highly to human engineering activities, such as road excavation and slope cutting. The minimum geohazard that can be recognized in the 0.5 m resolution DEM is about 900 m^(2). Meanwhile, the SVF visualization method is demonstrated to be a great alternative to the classical hillshaded DEM method when it comes to the determination of geomorphological properties of geohazard. Results of this study highlight the importance of Li DAR data for creating complete and accurate geohazard inventories, which can then be used for the production of reliable susceptibility and hazard maps and thus contribute to a better understanding of the movement processes and reducing related losses.

关键词： geohazard geohazard inventory airborne Li DAR sky view factor remote sensing interpretation complex mountainous areas

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Impacts of the Urban Spatial Landscape in Beijing on Surface and Canopy Urban Heat Islands

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Journal of Meteorological Research 2022年第6期36卷 882-899页

作者： Yonghong LIU Yongming XU Yeping ZHANG Xiuzhen HAN Fuzhong WENG Chunyi XUAN Wenjun SHU CMA Earth System Modeling and Prediction Centre China Meteorological Administration(CMA)Beijing 100081 State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesChina Meteorological AdministrationBeijing 100081 School of Remote Sensing and Geomatics Engineering Nanjing University of Information Science&TechnologyNanjing 210044 National Satellite Meteorological Centre China Meteorological AdministrationBeijing 100081 Beijing Municipal ClimateCentre Beijing Meteorological ServiceBeijing 100089

How does the urban spatial landscape(USL)pattern affect the land surface urban heat islands(SUHIs)and canopy urban heat islands(CUHIs)?Based on satellite and meteorological observations,this case study compares the impacts of the USL pattern on SUHI and CUHI in the central urban area(CUA)of Beijing using the satellite land-surface-temperature product and hourly temperature data from automatic meteorological stations from 2009 to *** USL metrics—building height(BH),building density(BD),standard deviation of building height(BSD),floor area ratio(FAR),frontal area index(FAI),roughness length(RL),sky view factor(SVF),urban fractal dimension(FD),vegetation coverage(VC),impervious coverage(IC),and albedo(AB)—with a 500-m spatial resolution in the CUA are extracted for comparative *** results show that SUHI is higher than CUHI at night,and SUHI is only consistent with CUHI at spatial-temporal scales at night,particularly in ***,all 11 metrics are strongly correlated with both the SUHI and CUHI at night,with stronger correlation between most metrics and ***,AB,and SVF have the greatest impact on both the SUHI and *** SUHI and CUHI values tend to appear in areas with BD≥0.26,VC≤0.09,AB≤0.09,and SVF≤*** summer,most metrics have a greater impact on the SUHI than CUHI;the opposite is observed in *** variation is affected primarily by VC in summer and by VC and AB in winter,which is different for the CUHI *** collective contribution of all 11metrics to SUHI spatial variation in summer(61.8%)is higher than that to CUHI;however,the opposite holds in winter and for the entire year,where the cumulative contribution of the factors accounts for 66.6%and 49.6%,respectively,of the SUHI variation.

关键词： surface urban heat island canopy urban heat island vegetation coverage albedo sky view factor building density Beijing

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