Heat flux data collected from the Baiyangdian Heterogeneous Field Experiment were analyzed using the footprint method. High resolution （25 m） Landsat-5 satellite imaging was used to determine the land cover as one o...Heat flux data collected from the Baiyangdian Heterogeneous Field Experiment were analyzed using the footprint method. High resolution （25 m） Landsat-5 satellite imaging was used to determine the land cover as one of four surface types： farmland, lake, wetland, or village. Data from two observation sites in September 2005 were used. One site （Wangjiazhai） was characterized by highly heterogeneous surfaces in the central area of the Baiyangdian： lake/wetland. The other site （Xiongxian） was on land with more uniform surface cover. An improved Eulerian analytical flux footprint model was used to determine “source areas” of the heat fluxes measured at towers located at each site from surrounding landscapes of mixed surface types. In relative terms results show that wetland and lake areas generally contributed most to the observed heat flux at Wangjiazhai, while farmland contributed most at Xiongxian. Given the areal distribution of surface type contributions, calculations were made to obtain the magnitudes of the heat flux from lake, wetland and farmland to the total observed flux and apportioned contributions of each surface type to the sensible and latent heat fluxes. Results show that on average the sensible heat flux from wetland and farmland were comparable over the diurnal cycle, while the latent heat flux from farmland was somewhat larger by about 30-50 W m-2 during daytime. The latent and sensible fluxes from the lake source in daytime were about 50 W m-2 and 100 W m-2 less, respectively, than from wetland and farmland. The results are judged reasonable and serve to demonstrate the potential for flux apportionment over heterogeneous surfaces.展开更多
Spatial heterogeneity poses a major challenge for the appropriate interpretation of eddy covariance data. The quantification of footprint climatology is fundamental to improving our understanding of carbon budgets, as...Spatial heterogeneity poses a major challenge for the appropriate interpretation of eddy covariance data. The quantification of footprint climatology is fundamental to improving our understanding of carbon budgets, assessing the quality of eddy covariance data, and upscaling the representativeness of a tower flux to regional or global scales. In this study, we elucidated the seasonal variation of flux footprint climatologies and the major factors that influence them using the analytical FSAM （Flux Source Area Model）, KM （Kormann and Meixner, 2001）, and H （Hsieh et al., 2000） models based on eddy covariance measurements at two and three times the canopy height at the Qianyanzhou site of ChinaFLUX in 2003. The differences in footprints among the three models resulted from different underlying theories used to construct the models. A comparison demonstrated that atmospheric stability was the main factor leading to differences among the three models. In neutral and stable conditions,the KM and FSAM values agreed with each other, but they were both lower than the H values. In unstable conditions, the agreement among the three models for rough surfaces was better than that for smooth surfaces, and the models showed greater agreement for a low measurement height than for a high measurement height. The seasonal flux footprint climatologies were asymmetrically distributed around the tower and corresponded well to the prevailing wind direction, which was north-northwest in winter and south-southeast in summer. The average sizes of the 90% flux footprint climatologies were 0.36 0.74 and 1.5-3.2 kin2 at altitudes of two and three times the canopy height, respectively. The average sizes were ranked by season as follows： spring 〉 summer 〉 winter 〉 autumn. The footprint climatology depended more on atmospheric stability on daily scale than on seasonal scale, and it increased with the increasing standard deviation of the lateral wind fluctuations.展开更多
[目的]分析橡胶林通量观测数据质量。[方法]根据农业部儋州热带农业资源与生态环境重点野外试验站50米高通量观测塔2010年前6个月连续的通量观测资料,应用Schmid(1994)的FSAM(Flux-Source Area Model)模式分析不同大气条件下橡胶林干季...[目的]分析橡胶林通量观测数据质量。[方法]根据农业部儋州热带农业资源与生态环境重点野外试验站50米高通量观测塔2010年前6个月连续的通量观测资料,应用Schmid(1994)的FSAM(Flux-Source Area Model)模式分析不同大气条件下橡胶林干季通量足迹与源区分布特征。[结果]不稳定条件下,传感器测得的通量信息源区比稳定条件时源区面积相对小;相同水平下非生长季的信息源区比生长季的信息源区大。在主风方向130°～270°,生长季不稳定条件下,通量测量的信息源区(P=80%)迎风方向范围在100～758m之间,垂直于迎风方向范围在-251～251m之间,非生长季不稳定条件下,迎风方向和垂直迎风方向的范围较均值略大些;生长季稳定条件下,分别为173～1858m,-534～534m,非生长季稳定条件下,迎风方向和垂直迎风方向的范围较均值略小些。风向在0°～130°、270°～360°时,相同大气条件下,其范围与主风向生长季的范围近似。[结论]该研究为进一步通量计算和分析奠定了基础。展开更多
选取2005年5月24日-6月18日在金塔开展的“绿洲系统能量与水分循环过程的观测实验”中的3层CSAT3的实验数据，应用Schmid的FSAM（The Flux-Source Area Model）模型，分析了不同观测高度的通量贡献源区分布以及观测高度对通量贡献源区...选取2005年5月24日-6月18日在金塔开展的“绿洲系统能量与水分循环过程的观测实验”中的3层CSAT3的实验数据，应用Schmid的FSAM（The Flux-Source Area Model）模型，分析了不同观测高度的通量贡献源区分布以及观测高度对通量贡献源区分布的影响，同时分析了不同大气层结条件下源区的分布以及稳定度对通量贡献源区分布的影响。结果表明,稳定条件下的通量贡献源区大于不稳定条件下的通量贡献源区，并且随着观测高度的增加通量贡献源区会显著增大。展开更多
将时间因素和生物碳通量纳入林产品生命周期碳足迹评估,通过动态生命周期分析法(Dynamic Life Cycle Assessment,DLCA),确定林产品生产、使用和废弃阶段替代化石能源的净温室气体减排和对森林碳损失的净弥补时间。首先,建立温室气体排...将时间因素和生物碳通量纳入林产品生命周期碳足迹评估,通过动态生命周期分析法(Dynamic Life Cycle Assessment,DLCA),确定林产品生产、使用和废弃阶段替代化石能源的净温室气体减排和对森林碳损失的净弥补时间。首先,建立温室气体排放和封存的动态生命周期清单,评估刨花板全生命周期的碳动态和碳足迹;其次,根据ISO 14040和PAS 2050标准提供的静态生命周期分析法分别核算包含与不包含碳储计算的碳足迹,量化时间因素和生物碳通量对于碳足迹结果差异的影响程度;最后,对比自然生长状态的森林碳汇情境,评估刨花板使用和废弃阶段替代化石燃料实现净气候减排所需的时间。研究表明:①时间因素和生物碳通量核算对碳足迹结果影响较大(223.34%),忽视时间因素会低估刨花板的减排贡献(18.98%)。②动态生命周期分析法可准确评估生物碳和温室气体排放的时间问题,但对时间范围非常敏感(75.19%和113.25%)。③生产、使用林产品以及林产品对化石能源的替代是实现长期气候减排的有效方式,在100a的时间范围能够弥补因森林砍伐造成的碳损失,从而实现碳中性。展开更多
文摘Heat flux data collected from the Baiyangdian Heterogeneous Field Experiment were analyzed using the footprint method. High resolution （25 m） Landsat-5 satellite imaging was used to determine the land cover as one of four surface types： farmland, lake, wetland, or village. Data from two observation sites in September 2005 were used. One site （Wangjiazhai） was characterized by highly heterogeneous surfaces in the central area of the Baiyangdian： lake/wetland. The other site （Xiongxian） was on land with more uniform surface cover. An improved Eulerian analytical flux footprint model was used to determine “source areas” of the heat fluxes measured at towers located at each site from surrounding landscapes of mixed surface types. In relative terms results show that wetland and lake areas generally contributed most to the observed heat flux at Wangjiazhai, while farmland contributed most at Xiongxian. Given the areal distribution of surface type contributions, calculations were made to obtain the magnitudes of the heat flux from lake, wetland and farmland to the total observed flux and apportioned contributions of each surface type to the sensible and latent heat fluxes. Results show that on average the sensible heat flux from wetland and farmland were comparable over the diurnal cycle, while the latent heat flux from farmland was somewhat larger by about 30-50 W m-2 during daytime. The latent and sensible fluxes from the lake source in daytime were about 50 W m-2 and 100 W m-2 less, respectively, than from wetland and farmland. The results are judged reasonable and serve to demonstrate the potential for flux apportionment over heterogeneous surfaces.
基金Supported by the National Basic Research and Development(973)Program of China(2012CB416903)National Natural Science Foundation of China(31470500 and 31290221)Knowledge Innovation Project of the Chinese Academy of Sciences(KZCX2-EW-QN305)
文摘Spatial heterogeneity poses a major challenge for the appropriate interpretation of eddy covariance data. The quantification of footprint climatology is fundamental to improving our understanding of carbon budgets, assessing the quality of eddy covariance data, and upscaling the representativeness of a tower flux to regional or global scales. In this study, we elucidated the seasonal variation of flux footprint climatologies and the major factors that influence them using the analytical FSAM （Flux Source Area Model）, KM （Kormann and Meixner, 2001）, and H （Hsieh et al., 2000） models based on eddy covariance measurements at two and three times the canopy height at the Qianyanzhou site of ChinaFLUX in 2003. The differences in footprints among the three models resulted from different underlying theories used to construct the models. A comparison demonstrated that atmospheric stability was the main factor leading to differences among the three models. In neutral and stable conditions,the KM and FSAM values agreed with each other, but they were both lower than the H values. In unstable conditions, the agreement among the three models for rough surfaces was better than that for smooth surfaces, and the models showed greater agreement for a low measurement height than for a high measurement height. The seasonal flux footprint climatologies were asymmetrically distributed around the tower and corresponded well to the prevailing wind direction, which was north-northwest in winter and south-southeast in summer. The average sizes of the 90% flux footprint climatologies were 0.36 0.74 and 1.5-3.2 kin2 at altitudes of two and three times the canopy height, respectively. The average sizes were ranked by season as follows： spring 〉 summer 〉 winter 〉 autumn. The footprint climatology depended more on atmospheric stability on daily scale than on seasonal scale, and it increased with the increasing standard deviation of the lateral wind fluctuations.
基金Supported by the Fundamental Research Funds for Rubber Research Institute,CATAS (1630022011013 )Hainan Natural Science Foundation (807045)Running Costs of Danzhou Key Field Station of Observation and Research for Tropical Agricultural Resources and Environments,Ministry of Agriculture~~
文摘[目的]分析橡胶林通量观测数据质量。[方法]根据农业部儋州热带农业资源与生态环境重点野外试验站50米高通量观测塔2010年前6个月连续的通量观测资料,应用Schmid(1994)的FSAM(Flux-Source Area Model)模式分析不同大气条件下橡胶林干季通量足迹与源区分布特征。[结果]不稳定条件下,传感器测得的通量信息源区比稳定条件时源区面积相对小;相同水平下非生长季的信息源区比生长季的信息源区大。在主风方向130°～270°,生长季不稳定条件下,通量测量的信息源区(P=80%)迎风方向范围在100～758m之间,垂直于迎风方向范围在-251～251m之间,非生长季不稳定条件下,迎风方向和垂直迎风方向的范围较均值略大些;生长季稳定条件下,分别为173～1858m,-534～534m,非生长季稳定条件下,迎风方向和垂直迎风方向的范围较均值略小些。风向在0°～130°、270°～360°时,相同大气条件下,其范围与主风向生长季的范围近似。[结论]该研究为进一步通量计算和分析奠定了基础。
文摘选取2005年5月24日-6月18日在金塔开展的“绿洲系统能量与水分循环过程的观测实验”中的3层CSAT3的实验数据，应用Schmid的FSAM（The Flux-Source Area Model）模型，分析了不同观测高度的通量贡献源区分布以及观测高度对通量贡献源区分布的影响，同时分析了不同大气层结条件下源区的分布以及稳定度对通量贡献源区分布的影响。结果表明,稳定条件下的通量贡献源区大于不稳定条件下的通量贡献源区，并且随着观测高度的增加通量贡献源区会显著增大。
