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首页> 外文期刊>Journal of the Atmospheric Sciences >The structure of the near-neutral atmospheric surface layer
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The structure of the near-neutral atmospheric surface layer

机译：接近中性的大气表层的结构

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Recent observational data (turbulence variables by sonic anemometers and three-dimensional flow pattern by Doppler lidar), obtained during the Cooperative Atmosphere Surface Exchange Study field campaign in October 1999 (CASES-99), show evidence of a layered structure of the near-neutral surface layer: (i) the eddy surface layer (ESL), which is the lower sublayer where blocking of impinging eddies is the dominating mechanism; and (ii) the shear surface layer (SSL), which is an intermediate sublayer, where shear affects the isotropy of turbulence. The origin of the eddies impinging from aloft (probably from the SSL) down to the ESL is preliminarily addressed in this study, since the Doppler lidar data show evidence of linearly organized eddies embedded in the surface layer (i.e., about 100-m vertical extent) and horizontally spaced by about 300 m. This is consistent with theories predicting that the primary mechanism of eddy motion in high Reynolds number wall layers is "top-down." The layered structure of the surface layer also has a visible effect on vertical profiles of vertical velocity variance ((w(2)) over bar) and momentum transport. In the ESL, (w(2)) over bar scales as z(2/3) while it is constant or slightly decreases within the SSL. Concerning momentum transport, ejections contribute identically to the momentum flux as do sweeps in the ESL, whereas in the SSL, ejections give about 50% higher relative contribution. [References: 68]
机译：在1999年10月的“合作大气表面交换研究”野外活动（CASES-99）中获得的最新观测数据（由声速计测量的湍流变量和多普勒激光雷达的三维流动模式）显示了接近中性的分层结构的证据。表面层：（i）涡流表面层（ESL），它是下层，其中撞击涡流的阻塞是主要机制; （ii）剪切表面层（SSL），它是一个中间子层，其中剪切会影响湍流的各向同性。由于多普勒激光雷达数据显示出表面层中埋藏着线性组织的涡流（即垂直方向约100米）的证据，因此本研究初步解决了从高空（可能从SSL）到ESL的涡流的起源。 ），水平间隔约300 m。这与预测高雷诺数壁层中涡流运动的主要机理是“自上而下”的理论相一致。表面层的分层结构还对垂直速度方差（条形上的（w（2）））和动量传递的垂直轮廓具有可见的影响。在ESL中，（w（2））在bar上缩放为z（2/3），而在SSL范围内它是恒定的或略有减小。关于动量传输，喷射对动量通量的贡献与ESL中的扫掠相同，而在SSL中，喷射对动量通量的相对贡献高出约50％。 [参考：68]

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