Measurements of a Dusty Density Current in the Western Sonoran Desert
Measurements of a Dusty Density Current in the Western Sonoran Desert
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DOI：
10.1029/2021jd035830
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
A. Evan;W. Porter;R. Clemensha;A. Kuwano;R. Frouin
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文献类型：
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作者：
A. Evan;W. Porter;R. Clemensha;A. Kuwano;R. Frouin
在这里，我们展示了对2020年2月22日在索诺兰沙漠西北部发生的沙尘暴的观测结果。现场和遥感测量以及数值模拟的结果表明，冷锋地形降水在逆风山脉上的蒸发冷却产生了密度流，当密度流在发射的沙漠表面上移动时，发生了粉尘的上升。由于密度流中充满了粉尘，在初始粉尘排放事件下风25 km处的ceilometer上获得的气溶胶后向散射和消光垂直剖面时间序列显示密度流结构发育良好，包括垂直范围为1.2 km的锋面翻转。Ceilometer测量和探测结果表明，密度电流体深度为400-500米，呈现出两层结构，由正剪切且多尘的下层和负剪切且原始的上层组成。密度流冷池顶部的开尔文-亥姆霍兹不稳定性在尘埃和原始天空界面层的高度产生了准规则振荡。该界面层高度的脊和槽分别耦合地表风速和近地表尘埃浓度的最大值和最小值，尘埃浓度峰值位于界面层脊的正下方。这些结果证实了密度流的粉尘排放和输送模式研究的一些发现，并表明密度流的内部循环改变了粉尘排放的时间和电流体内粉尘浓度的模式。
Here we present observations of a dust storm that occurred on 22 February 2020 in the northwestern Sonoran Desert. In‐situ and remotely sensed measurements and output from numerical simulations suggest that evaporative cooling from cold frontal orographic precipitation spilling over an upwind mountain range generated a density current, with dust uplift occurring as the density current traveled over the emissive desert surface. Because the density current was laden with dust, time series of vertical profiles of aerosol backscatter and extinction from a ceilometer located 25 km downwind of the initial dust emission event show a well‐developed density current structure, including an overturning frontal head with a vertical extent of 1.2 km. Ceilometer measurements and soundings suggest a density current body depth of 400–500 m exhibiting a two‐layer structure that consisted of a positively sheared and dusty lower‐level, and a negatively sheared and pristine upper level. Kelvin‐Helmholtz instability at the top of the density current cold pool generated quasi‐regular oscillations in the height of the dust and pristine‐sky interfacial layer. Ridges and troughs in the height of this interfacial layer were coupled to maxima and minima in surface wind speed and near surface dust concentrations, respectively, with peak dust concentrations located directly under the interfacial layer ridges. These results corroborate several findings from model studies of dust emission and transport by density currents, and suggest that the internal circulation of a density current modifies the timing of dust emission and the patterns of dust concentration within the current body.