...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Agricultural and Forest Meteorology >Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes?
【24h】

Is friction velocity the most appropriate scale for correcting nocturnal carbon dioxide fluxes?

机译：摩擦速度是校正夜间二氧化碳通量的最合适尺度吗？

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The use of friction velocity u. as the turbulence scale for correcting eddy-covariance carbon dioxide fluxes in low-mixing conditions is questioned. This is done because U. is, itself, a flux and, therefore, its value is highly dependent on the temporal scale used for the analysis. The multiresolution decomposition is applied to data from three different ecosystems in Brazil, to show that u. is well behaved and related to the turbulent mixing only up to the scale that separates the turbulent mixing from the low-frequency exchange. For larger temporal scales, mesoscale fluxes may induce large variability in the friction velocity, so that time series with low turbulent mixing may show an elevated value for u., and vice-versa. We propose, as an alternative, the use of sigma(omega), the standard-deviation of the vertical velocity fluctuations. It is shown that sigma(omega) has no variability within the mesoscale range and that, therefore, it is a much better scale to quantify the turbulent exchange than u. The relationship between the two velocity scales is shown to depend on the scale and to be universal for the scales of the turbulent exchange. It is shown that curves of the turbulent carbon dioxide fluxes as a function of the turbulence scale are smoothed when using the friction velocity. Using sigma(omega) instead of u. in data filtering procedures has two main consequences: easier determination of the threshold for filtering and larger respiration rates of the series classified as turbulent. The improvement is larger for sites where very stable conditions are common. (c) 2008 Elsevier B.V. All rights reserved.
机译：利用摩擦速度u。由于在低混合条件下用于校正涡流-协方差二氧化碳通量的湍流尺度受到质疑。这样做是因为U.本身就是一个通量，因此其值高度依赖于用于分析的时间尺度。多分辨率分解应用于来自巴西三个不同生态系统的数据，显示出u。湍流表现良好，并且仅与将湍流混合与低频交换区分开的比例有关。对于较大的时间尺度，中尺度通量可能会引起摩擦速度的较大变化，因此具有低湍流混合的时间序列可能显示出较高的u值，反之亦然。作为替代方案，我们建议使用sigma（Ω），即垂直速度波动的标准偏差。结果表明，σ在中尺度范围内没有变化，因此，量化湍流交换的尺度比u好得多。示出了两个速度标度之间的关系取决于标度并且对于湍流交换的标度是通用的。结果表明，当使用摩擦速度时，湍流二氧化碳通量的曲线作为湍流尺度的函数是平滑的。使用sigma（omega）代替u。数据过滤程序中的数据有两个主要结果：更容易确定过滤阈值，并且将较大的呼吸速率归为湍流。对于条件非常稳定的站点，改进更大。 （c）2008 Elsevier B.V.保留所有权利。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号