Turbulent exchange above a pine forest II. Organized structures
Turbulent exchange above a pine forest II. Organized structures
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松树林上空的湍流交换 II.
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
U. Högström
中科院分区：
文献类型：
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作者：
H. Bergström;U. Högström
用条件抽样技术分析了两次100分钟的松林上空湍流大气风场、温度场和湿度场的资料。借助温度时间序列，识别斜坡事件，并对所有场进行平均，以去除较小尺度的湍流和随机低频湍流，并绘制以这种方式显示的有组织结构。结果表明，由这些斜坡事件所确定的动量、热量和湿度的湍流通量实际上占总通量的很大一部分，在实际事件中约占90%，斜坡事件的持续时间和斜坡事件之间的时间平均分别约为35 s和100 s。这些时期也被发现在uw-，wT-和wq-cospectrum，不仅在本文中分析的数据，但在大部分的所有白天的数据从这个森林网站（约80运行60或100分钟）。这表明所描述的斜坡事件是一种相当普遍的现象。有组织的结构也有显着的相似之处，在实验室中观察到的近壁结构。
Data from two 100-min runs on the turbulent atmospheric wind, temperature and humidity fields above a pine forest have been analysed using conditional sampling techniques. With the aid of the temperature time series, ramp events were identified and all fields were averaged in order to remove smaller scale turbulence and random low-frequency turbulence, and to map the organized structures revealed in this way. It is shown that the turbulent fluxes of momentum, heat and humidity, determined from these ramp-events, in fact constitute a large part of the total fluxes, about 90% during the actual events.On average, the duration of and the time between ramps were found to be about 35 s and 100 s, respectively. These periods were also found in the uw-, wT- and wq-cospectra, not only in the data analysed in this paper, but in the major part of all day-time data from this forest site (about 80 runs of 60 or 100 min). This indicates that the ramp events described arc a rather common phenomenon. The organized structures also have remarkable resemblance to near-wall structures observed in the laboratory.