Fine Structure, Instabilities, and Turbulence in the Lower Atmosphere: High-Resolution In Situ Slant-Path Measurements with the DataHawk UAV and Comparisons with Numerical Modeling
Fine Structure, Instabilities, and Turbulence in the Lower Atmosphere: High-Resolution In Situ Slant-Path Measurements with the DataHawk UAV and Comparisons with Numerical Modeling
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DOI：
10.1175/jtech-d-16-0037.1
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发表时间：
2018-03-01
影响因子：
2.2
通讯作者：
Werne, Joe
中科院分区：
文献类型：
--
作者：
Balsley, Ben B.;Lawrence, Dale A.;Werne, Joe
描述了一种用于对流层低层高分辨率现场测量的新平台，并对其性能进行了演示。该平台是由GPS控制的小型DataHawk无人机系统(UAS)，于2012年10月11日在犹他州Dugway试验场的分层大气条件下进行了测量。测量包括温度和水平风矢量的螺旋形垂直廓线，由此推断出位温θ、机械能量耗散率epsilon、Brunt-Vasala频率N、温度结构参数C-T(2)、Thorpe和Ozmidov等级L-T和L-O以及Richardson数Ri。这些量在50-400m的剖面上显示出较大尺度上的明显重力波调制，在30-100m尺度上持续的板层结构，以及几层显示出大Esilon、C-T(2)、L-T和小Ri的显著相关性。较小尺度的流动特征表明，局部重力波和开尔文-亥姆霍兹不稳定性表现出很强的相关性，产生显著的垂直位移，并在较小尺度上引发湍流和混合。将这些结果与相似多尺度动力学的直接数值模拟结果进行了比较，结果表明，实测层特征和演变、小尺度动力学和湍流强度与实测值和模型层特征十分吻合。具体地说，使用通过DNS的虚拟采样路径并将这些与DataHawk测量结果进行比较，对作为特定DataHawk采样轨迹的结果的推断数量中的潜在偏差和/或对潜在动态的误解进行详细检查。
A new platform for high-resolution in situ measurements in the lower troposphere is described and its capabilities are demonstrated. The platform is the small GPS-controlled DataHawk unmanned aerial system (UAS), and measurements were performed under stratified atmospheric conditions at Dugway Proving Ground, Utah, on 11 October 2012. The measurements included spiraling vertical profiles of temperature and horizontal wind vectors, from which the potential temperature theta, mechanical energy dissipation rate epsilon, Brunt-Vasala frequency N, temperature structure parameter C-T(2), Thorpe and Ozmidov scales L-T and L-O, and Richardson number Ri were inferred. Profiles of these quantities from similar to 50 to 400 m reveal apparent gravity wave modulation at larger scales, persistent sheet-and-layer structures at scales of similar to 30-100 m, and several layers exhibiting significant correlations of large epsilon, C-T(2), L-T, and small Ri. Smaller-scale flow features suggest local gravity waves and Kelvin-Helmholtz instabilities exhibiting strong correlations, yielding significant vertical displacements and inducing turbulence and mixing at smaller scales. Comparisons of these results with a direct numerical simulation (DNS) of similar multiscale dynamics indicate close agreement between measured and modeled layer character and evolution, small-scale dynamics, and turbulence intensities. In particular, a detailed examination of the potential biases in inferred quantities and/or misinterpretation of the underlying dynamics as a result of the specific DataHawk sampling trajectory is carried out using virtual sampling paths through the DNS and comparing these with the DataHawk measurements.