The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency am...The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency among scalars to estimate turbulent fluxes using the flux-variance method. We investigated these issues using eddycovariance measurements over an open, homogeneous and flat grassland in the eastern Tibetan Plateau in summer under intermediate hydrological conditions during rainy season. In unstable conditions, the temperature, water vapor, and CO2 followed the flux-variance similarity relation, but did not show in precisely the same way due to different roles （active or passive） of these scalars. Similarity constants of temperature, water vapor and CO2 were found to be 1.12, 1.19 and 1.17, respectively. Heat transportation was more eft% cient than water vapor and CO2. Based on the estimated sensible heat flux, five parameterization methods of relative transport efficiency of heat to water vapor and CO2 were examined to estimate latent heat and CO2 fluxes. The strategy of local determination of flux-variance similarity relation is recommended for the estimation of latent heat and CO2 fluxes. This approach is better for representing the averaged relative transport efficiency, and technically easier to apply, compared to other more complex ones.展开更多
地表能量平衡是地-气间相互作用的重要方式,随着涡旋相关技术在物质传输和能量交换研究中的广泛应用,如何评价其观测数据的可信度则变得尤为重要。利用成都平原温江大气边界层观测站2008年观测资料,分析了农田下垫面上能量收支各分量和...地表能量平衡是地-气间相互作用的重要方式,随着涡旋相关技术在物质传输和能量交换研究中的广泛应用,如何评价其观测数据的可信度则变得尤为重要。利用成都平原温江大气边界层观测站2008年观测资料,分析了农田下垫面上能量收支各分量和辐射平衡各分量的特征及变化规律,并运用最小二乘法(Ordinary Least Squares,OLS)线性回归方法和能量平衡比率(Energy Balance Ratio,EBR)方法对湍流通量(感热与潜热通量之和)与有效能量(净辐射与地表土壤热通量之差)之间的关系进行了研究,得到了一些有意义的结果。展开更多
Eddy-covariance observations from the Beijing 325-m meteorological tower are used to evaluate the effects of coordinate rotation on the turbulent exchange of momentum and scalars during wintertime haze pollution(Janua...Eddy-covariance observations from the Beijing 325-m meteorological tower are used to evaluate the effects of coordinate rotation on the turbulent exchange of momentum and scalars during wintertime haze pollution(January-February 2013). Two techniques are used in the present evaluation; namely, the natural wind coordinate(NWC) and the planar fit coordinate(PFC), with the latter being applied by means of two methods for linear regression(i.e., overall and sector-wise). The different techniques show a general agreement in both turbulent fluxes and transport efficiencies, especially evident at the lower, 140-m level above the ground(compared to the higher, 280-m level), perhaps implying that the selection of a technique for coordinate rotation(NWC or PFC) is less of a concern for a sufficiently low level, despite the complexities of urban terrain. Additionally, sector-wise regression is a recommended approach for practical application of the PFC in a complex urban environment subjected to particulate pollution, because this method is found to produce a better correlation between the mean vertical velocity at the 140- and 280-m heights.展开更多
Using the eddy covariance method,from 1 July2003 to 30 June 2004, we conducted the observation andanalysis of ecosystem CO2 flux in 3 types of alpine meadowvegetation (Kobresia humilis, Potentilla fruticosa shrub andK...Using the eddy covariance method,from 1 July2003 to 30 June 2004, we conducted the observation andanalysis of ecosystem CO2 flux in 3 types of alpine meadowvegetation (Kobresia humilis, Potentilla fruticosa shrub andKobresia tibetica swamp meadows) on the Qinghai-TibetanPlateau. The results show that the Kobresia humilis meadow,the shrub meadow and the swamp meadow’s highest CO2uptake rates are 16.78, 10.42 and 16.57 μmol·m?2·s?1respectively, while their highest CO2 release rates are 8.22,7.73 and 18.67 μmol·m?2·s?1 respectively. The Kobresiahumilis meadow and shrub meadow’s annual atmosphericuptakes are 282 g CO2/m2 and 53 g CO2/m2, respectively,while swamp meadow’s annual atmospheric release is 478 gCO2/m2. This proves that the Kobresia humilis meadow andthe shrub meadow on the Qinghai-Tibetan Plateau haverelatively low potential for CO2 uptake and release comparedto C4 grasslands, a number of lowland grasslands, andforests. Moreover, swamp meadow has relatively high releasepotential. This, in turn, reveals clear differences in carbonsource/sink between different types of vegetation in theQinghai-Tibetan Plateau alpine meadow ecosystem. Thesedifferences are mainly brought by differences in thevegetations’ photosynthetic capacity and soil respiration.展开更多
基金funding frown the Chinese National Key Programme for Developing Basic Sciences，the National Natural Science Foundation of China，the Key Program of the Chinese Academy of Sciences，the National Natural Science Foundation of China，the Foundation for Excellent Young Scholars of CAREERI
文摘The flux-variance similarity relation and the vertical transfer of scalars exhibit dissimilarity over different types of surfaces, resulting in different parameterization approaches of relative transport efficiency among scalars to estimate turbulent fluxes using the flux-variance method. We investigated these issues using eddycovariance measurements over an open, homogeneous and flat grassland in the eastern Tibetan Plateau in summer under intermediate hydrological conditions during rainy season. In unstable conditions, the temperature, water vapor, and CO2 followed the flux-variance similarity relation, but did not show in precisely the same way due to different roles （active or passive） of these scalars. Similarity constants of temperature, water vapor and CO2 were found to be 1.12, 1.19 and 1.17, respectively. Heat transportation was more eft% cient than water vapor and CO2. Based on the estimated sensible heat flux, five parameterization methods of relative transport efficiency of heat to water vapor and CO2 were examined to estimate latent heat and CO2 fluxes. The strategy of local determination of flux-variance similarity relation is recommended for the estimation of latent heat and CO2 fluxes. This approach is better for representing the averaged relative transport efficiency, and technically easier to apply, compared to other more complex ones.
文摘地表能量平衡是地-气间相互作用的重要方式,随着涡旋相关技术在物质传输和能量交换研究中的广泛应用,如何评价其观测数据的可信度则变得尤为重要。利用成都平原温江大气边界层观测站2008年观测资料,分析了农田下垫面上能量收支各分量和辐射平衡各分量的特征及变化规律,并运用最小二乘法(Ordinary Least Squares,OLS)线性回归方法和能量平衡比率(Energy Balance Ratio,EBR)方法对湍流通量(感热与潜热通量之和)与有效能量(净辐射与地表土壤热通量之差)之间的关系进行了研究,得到了一些有意义的结果。
基金funded by the National Basic Research Program of China(Grant No.2014CB447900)National High Technology Research and Development Program(Grant No.2014AA06A512)Ministry of Environmental Protection of China through its Special Funds for Scientific Research on Public Welfare(Grant No.201409001)
文摘Eddy-covariance observations from the Beijing 325-m meteorological tower are used to evaluate the effects of coordinate rotation on the turbulent exchange of momentum and scalars during wintertime haze pollution(January-February 2013). Two techniques are used in the present evaluation; namely, the natural wind coordinate(NWC) and the planar fit coordinate(PFC), with the latter being applied by means of two methods for linear regression(i.e., overall and sector-wise). The different techniques show a general agreement in both turbulent fluxes and transport efficiencies, especially evident at the lower, 140-m level above the ground(compared to the higher, 280-m level), perhaps implying that the selection of a technique for coordinate rotation(NWC or PFC) is less of a concern for a sufficiently low level, despite the complexities of urban terrain. Additionally, sector-wise regression is a recommended approach for practical application of the PFC in a complex urban environment subjected to particulate pollution, because this method is found to produce a better correlation between the mean vertical velocity at the 140- and 280-m heights.
基金This work was supported by the Chinese Acad-emy of Science's Innovation Program(Grant No.KZCX1-SW-01-01A5)the 973.Program(Grant No.2002cb4 125ol)+1 种基金two joint Sino-Japanese projects:“Asia-Pacific Environmental Innovation Strategy Project(APEIS)""Research on the Effects of Carbon Dynamics and Global warming on Temperate Highland Grasslands”
文摘Using the eddy covariance method,from 1 July2003 to 30 June 2004, we conducted the observation andanalysis of ecosystem CO2 flux in 3 types of alpine meadowvegetation (Kobresia humilis, Potentilla fruticosa shrub andKobresia tibetica swamp meadows) on the Qinghai-TibetanPlateau. The results show that the Kobresia humilis meadow,the shrub meadow and the swamp meadow’s highest CO2uptake rates are 16.78, 10.42 and 16.57 μmol·m?2·s?1respectively, while their highest CO2 release rates are 8.22,7.73 and 18.67 μmol·m?2·s?1 respectively. The Kobresiahumilis meadow and shrub meadow’s annual atmosphericuptakes are 282 g CO2/m2 and 53 g CO2/m2, respectively,while swamp meadow’s annual atmospheric release is 478 gCO2/m2. This proves that the Kobresia humilis meadow andthe shrub meadow on the Qinghai-Tibetan Plateau haverelatively low potential for CO2 uptake and release comparedto C4 grasslands, a number of lowland grasslands, andforests. Moreover, swamp meadow has relatively high releasepotential. This, in turn, reveals clear differences in carbonsource/sink between different types of vegetation in theQinghai-Tibetan Plateau alpine meadow ecosystem. Thesedifferences are mainly brought by differences in thevegetations’ photosynthetic capacity and soil respiration.
