Measurements of level-crossing statistics of concentration fluctuations in plumes dispersing in the atmospheric surface layer
Measurements of level-crossing statistics of concentration fluctuations in plumes dispersing in the atmospheric surface layer
复制标题
大气表层羽流浓度波动的跨越统计测量
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
J. Bowers
中科院分区：
文献类型：
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作者：
E. Yee;R. Chan;P. Kosteniuk;G. Chandler;C. Biltoft;J. Bowers
研究了羽流在大气中扩散过程中浓度波动的水平交叉点和局部极值的统计。一组浓度波动示踪实验用于测量相对于浓度交叉水平范围的上交叉间隔（连续浓度爆发之间的到达时间）、偏移持续时间（浓度爆发的持续时间或宽度）和浓度幅度（连续上交叉之间的最大浓度和最小浓度之差）的统计特性。重点研究了顺风距离和大气分层对平交道口统计的影响。结果表明，增加大气稳定性对平交道口统计量的影响与增加离源距离的影响相似，即稳定层的平交道口浓度波动统计量与中性层的平交道口浓度波动统计量相似，但在更大的下风距离上。研究还发现，浓度水平连续上升交叉点之间的间隔分布，以及跨越浓度水平的偏移持续时间，可以用对数正态分布来近似，而浓度振幅的分布最好用伽马分布来表征。讨论了这些结果对浓度波动的平交道口统计建模的一些意义。
The statistics of level crossings and local extremes in concentration fluctuations in plumes dispersing in the atmosphere have been investigated. A set of concentration fluctuation tracer experiments has been utilized to measure the statistical propertics of the upcrossing interval (inter-arrival time between consecutive concentration bursts), excursion duration (persistence or width of concentration bursts), and concentration amplitude (difference between the maximum and minimum concentrations between successive upcrossings) with respect to a range of concentration crossing levels. In particular, the effect of downwind distance and atmospheric stratification on the level-crossing statistics has been studied in detail. It is shown that the effect of increasing atmospheric stability on level-crossing statistics is similar to the effect of increasing distance from the source in the sense that level-crossing statistics of concentration fluctuations in stable stratification resemble those in neutral stratification, but at a greater downwind distance. It is also found that the distribution of the interval between consecutive upcrossings of a concentration level, as well as the duration of an excursion across a concentration level, can be approximated by a lognormal distribution, whereas the distribution of the concentration amplitude is best characterized by a gamma distribution. Some implications of these results for the modeling of level-crossing statistics of concentration fluctuations are discussed.