Saharan dust plume charging observed over the UK
Saharan dust plume charging observed over the UK
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DOI：
10.1088/1748-9326/aabcd9
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发表时间：
2018-05-01
影响因子：
6.7
通讯作者：
Bennett, Alec J.
中科院分区：
文献类型：
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作者：
Harrison, R. Giles;Nicoll, Keri A.;Bennett, Alec J.
2017年10月16日，一股撒哈拉沙尘和伊比利亚烟雾穿过英国南部，被卷入一场起源于飓风奥菲利亚的大西洋气旋。高空的尘埃柱被广泛注意到，因为它足够密集，使太阳的视觉外观变红。从阅读和奇尔博尔顿的云高计得到的后向散射时间序列显示出两股烟羽：一股被向上带到2.5公里处，另一股在800米以下进入边界层，其间有一个明显的缝隙。大约50厘米（-1）的粒子稳定下降持续了整个上午，粗糙模式的粒子到达了表面。含有尘埃的羽流经常被观察到带有强烈的电荷，通常是通过摩擦效应。这个羽流经过了位于布里斯托、奇尔博尔顿和阅读的大气电场传感器。在这三个地点的一致测量表明负羽流电荷。较低的边缘羽流电荷密度为（-8.0 +/- 3.3）nCm（-2），这是几倍大于典型的层状水云，这意味着一个活跃的原位电荷产生机制，如湍流摩擦起电。协调世界时14时12分，向烟柱发射了一个测量温度和湿度的气象无线电探空仪，特别装有电荷和湍流传感器。这种检测在边界层和上羽流区域中检测到电荷，并且在整个大气最低4公里处观察到强烈的湍流混合。与模拟值相比，颗粒沉降的清晰缝隙区域非常干燥，下方空气中间歇性地形成水云。尘埃的电学方面应包括在数值模型中，特别是与电荷有关的对云微物理特性的影响，以准确地表示粒子的行为和迁移。
A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cms(-1) continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (-8.0 +/- 3.3) nCm(-2), which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere's lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.