Source/sink distributions of heat, water vapour, carbon dioxide and methane in a rice canopy estimated using Lagrangian dispersion analysis
Source/sink distributions of heat, water vapour, carbon dioxide and methane in a rice canopy estimated using Lagrangian dispersion analysis
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使用拉格朗日离散分析估计稻冠中热量、水蒸气、二氧化碳和甲烷的源/汇分布
DOI：
10.1016/s0168-1923(00)00158-1
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发表时间：
2000
影响因子：
6.2
通讯作者：
Joon Kim
中科院分区：
文献类型：
--
作者：
R. Leuning;O. Denmead;A. Miyata;Joon Kim
利用实测浓度廓线、指定的湍流场和对植物冠层标量湍流扩散的逆拉格朗日分析，导出了水稻冠层内热量、水汽、CO2和CH 4的源分布。在日本冈山进行的国际水稻试验IREX 96期间进行了测量。结果表明，在冠层顶部的热量，水汽和CH 4的累积通量是令人满意的，一旦他们各自的浓度分布使用简单的解析函数平滑。根据逆分析，在冠层内的五个等间距层中，每一层的水汽排放相对均匀，而感热通量很小（<100 Wm −2），并且是两种符号。甲烷通量的预测排放最强烈的下50%的冠层，预期从微孔分布沿着叶和叶鞘，CH 4损失的主要途径从土壤作物系统。没有平滑所需的CO2浓度分布和反分析提供的浓度分布的转折点之间的密切对应关系是从土壤/稻田水和低冠层的呼吸转换到净光合作用的上冠层。这些结果只能通过包括源对总浓度分布的近场和远场贡献来获得。在反演分析中忽略近场的贡献导致了虚假的源分布。当摩擦速度u*>0.1ms-1，大气稳定度近似为中性时，反演得到的冠层顶部热量、水汽、CO2和CH 4的累积通量与涡动相关直接观测结果吻合较好。当u*<0.1ms− 1且冠层内和冠层上方大气条件稳定时，反演方法得到的CO2和CH 4夜间通量超过冠层上方微气象观测值2-3倍。忽略这些稳定性效应将导致输运模型中的弥散系数（阻力的维数）被低估，从而导致通量被高估。进一步的工作是需要建立正确的程序，将稳定性的影响到反分析。
Source distributions for heat, water vapour, CO2and CH4within a rice canopy were derived using measured concentration profiles, a prescribed turbulence field and an inverse Lagrangian analysis of turbulent dispersion of scalars in plant canopies. Measurements were made during IREX96, an international rice experiment in Okayama, Japan. Results for the cumulative fluxes of heat, water vapour and CH4at the canopy top were satisfactory once their respective concentration profiles were smoothed using simple analytic functions. According to the inverse analysis, water vapour was emitted relatively uniformly by each of five equi-spaced layers within the canopy, whereas sensible heat fluxes were small (<100Wm−2) and of either sign. Methane fluxes were predicted to be emitted most strongly in the lower 50% of the canopy, as expected from the distribution of micropores along leaves and leaf sheaths, the major pathway for CH4loss from the soil–crop system. No smoothing was required for CO2concentration profiles and the inverse analysis provided close correspondence between the turning point in the concentration profile is the changeover from respiration by the soil/paddy water and lower canopy to net photosynthesis by the upper canopy. These results could only be obtained by including both the near- and far-field contributions of sources to the total concentration profile. Neglect of the near-field contribution in the inverse analysis led to spurious source distributions. Excellent agreement was obtained between cumulative fluxes of heat, water vapour, CO2and CH4at the top of the canopy from the inverse analysis and direct eddy covariance measurements when the friction velocity u*>0.1ms−1, and atmospheric stability was approximately neutral. Nocturnal fluxes of CO2and CH4from the inverse method exceeded micrometeorological measurements above the canopy by a factor of 2–3 when u*<0.1ms−1and stable atmospheric conditions prevailed within and above the canopy. Neglect of these stability effects will lead to an underestimate of the dispersion coefficients (dimension of resistances) in the transport model and hence an overestimate of the fluxes. Further work is required to establish the correct procedure for incorporating stability effects into the inverse analysis.