夜间稳定边界层中间歇性湍流热通量的提取及其谱特征

刘磊; 胡非; 程雪玲

doi:10.3878/j.issn.1006-9895.2012.12065

夜间稳定边界层中间歇性湍流热通量的提取及其谱特征

doi: 10.3878/j.issn.1006-9895.2012.12065

中国科学院大气物理研究所大气边界层物理和大气化学国家重点实验室, 北京 100029

基金项目: 国家自然科学基金资助项目41105005;国家重点基础研究发展计划资助项目2010CB951804;国家科技支撑计划资助项目2008BAC37B02

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出版历程
- 收稿日期: 2012-04-19
- 修回日期: 2012-06-07

Extraction of Intermittent Turbulent Heat Fluxes and Their Spectrum Characteristics in the Nocturnal Stable Boundary Layer

State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029

摘要

摘要: 在夜间稳定边界层中, 湍流热通量往往具有间歇性特征。在一阵阵出现的强度较大的湍流热通量之间, 混杂着弱噪声或其他微弱的难以辨识的高频脉动信号。为了研究间歇性湍流热通量的特征, 必须将这些无关信号剔除, 以提取出干净的湍流热通量。本文提出了一种新的提取间歇性湍流热通量的方法, 该方法通过分析湍流热通量的概率密度函数, 并与稳定分布进行比较, 湍流热通量的概率密度函数开始偏离稳定分布的位置, 即是间歇性湍流热通量开始出现的阈值。本文通过夜间稳定边界层外场试验数据的验证, 发现利用稳定分布确定的阈值可有效地提取出间歇性湍流热通量。在此基础之上, 本文对比了提取前后湍流热通量的功率谱, 发现提取后低频信号的方差所占比重下降, 而高频信号略有上升。此外, 间歇性湍流热通量在高频区的功率谱满足“-7/6”律。
- 夜间边界层 /
- 湍流热通量 /
- 间歇性 /
- 稳定分布 /
- 功率谱
Abstract: In the nocturnal stable boundary layer, turbulent heat fluxes are not continuous but rather intermittent. Intermittent heat fluxes are characterized by brief episodes of turbulent heat flux with intervening periods of relatively weak noise or immeasurably small fluctuations. Their characteristics should be studied by extracting them from experimental data with weak noise and other small fluctuations. In this paper, we propose a new method of extracting intermittent heat fluxes. In this method, the probability density function of intermittent turbulent fluxes is analyzed and compared with the stable distributions. A threshold is defined by the position at which the probability density function begins to deviate from the stable distribution. We find that intermittent turbulent heat fluxes can be effectively extracted from experimental data. On the basis of our results, we compare the power spectra of turbulent heat fluxes before and after extraction. We found that after extraction, the proportion of variance of the low-frequency signal decreases, but that of the high-frequency signal increases slightly. In addition, the power spectra follow a ?7/6 power law at higher frequencies.
- nocturnal stable boundary layer /
- intermittent turbulent heat flux /
- stable distribution /
- power spectrum /

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