Mechanism of the energy balance non-closure associated with eddy covariance fluxes

涡协方差通量能量平衡非闭合机制

• 批准号: 19510020
• 负责人: WATANABE Tsutomu
• 金额: $ 2.25万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2007
• 资助国家: 日本
• 起止时间: 2007 至 2009
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-19510020/
• 关键词: フラックス; 渦相関法; 熱収支; インバランス; タワー観測; 数値流体シミュレーション; LES

Undermeasure of the sensible and latent heat fluxes by the eddy covariance method is a world-wide common problem among the flux-monitoring tower sites. Analysis of a dataset from a broadleaf forest site in Kawagoe (Japan) revealed that significant undermeasure tended to occur under the condition of large net radiation and low wind speed. Numerical fluid dynamics simulations run for such conditions indicated that a single-point eddy-covariance measurement does not capture the flux's low-frequency components associated with quasi-stationary convections of spatial scale as large as the boundary layer depth, and thus underestimates the total flux. Observed dissimilarity between temperature's and water-vapor's low-frequency fluctuations supports this idea because it is consistent with the simulation results showing that hot and dry air entrained at the top of the boundary layer reaches the height of flux measurements (near the bottom of the boundary layer) owing to the large-scale convection and causes out-of-phase fluctuations of low frequencies.

涡协方差法显热和潜热通量测量不足是世界范围内通量监测塔站点的通病。对日本川越阔叶林站点数据集的分析表明，在净辐射大和风速低的情况下，往往会发生严重的测量不足。针对此类条件进行的数值流体动力学模拟表明，单点涡流协方差测量无法捕获与边界层深度一样大的空间尺度准稳态对流相关的通量低频分量，因此低估了总通量。观察到的温度和水蒸气低频波动之间的差异支持了这一想法，因为它与模拟结果一致，显示边界层顶部夹带的干热空气达到通量测量的高度（靠近边界底部）层）由于大规模对流而引起低频的异相波动。

项目成果

農薬ドリフト研究へのLESの利用

利用 LES 进行农药漂移研究

• 发表时间: 2007
• 作者: 渡辺 力

LES study on the structure of coherent eddies inducing predominant perturbations in velocities in the roughness sublayer over plant canopies

LES 研究引起植物冠层粗糙次层速度主要扰动的相干涡流结构

• 发表时间: 2009
• 作者: T. Watanabe

LES study on the structure of coherent eddies inducing predominant perturbations in velocities in the roughness sublayer over plant canopies

LES 研究引起植物冠层粗糙次层速度主要扰动的相干涡流结构

• 发表时间: 2009
• 作者: Watanabe; T.
• 通讯作者: T.

フラックス輸送に寄与する渦の姿と観測上の問題点

涡旋的出现导致通量传输和观测问题

• 发表时间: 2007
• 作者: 渡辺 力

植生-大気相互作用の観測とモデリングにおける問題

植被与大气相互作用的观测和建模问题

• 发表时间: 2008
• 作者: 渡辺力