Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top layer of liquid phase clouds
Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top layer of liquid phase clouds
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北极低层边界层云：液相云顶层单峰和双峰过冷液滴尺寸分布的原位测量和模拟
DOI：
10.5194/acp-15-617-2015
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发表时间：
2015
影响因子：
6.3
通讯作者：
S. Borrmann
中科院分区：
文献类型：
--
作者：
M. Klingebiel;A. Lozar;S. Molleker;R. Weigel;A. Roth;L. Schmidt;Jessica R. Meyer;A. Ehrlich;R. Neuber;M. Wendisch;S. Borrmann
抽象的。在2012年4月和5月的北极云冰垂直分布（VERDI）活动期间，在北极边界层云中进行了机载光学原位尺寸分布测量，特别强调了云顶层。一架装有仪器的Basler BT-67研究飞机在因纽维克上空飞行，飞越加拿大西北地区的麦肯齐河三角洲和博福特海。除了云粒子和水凝物大小光谱仪外，飞机还配备了用于气溶胶、辐射和其他参数的仪器。在云内，主要是液相北极层积云的单峰形状的液滴大小分布进行了观察。随着云内高度的增加，雾滴平均直径从10 μ m增加到20 μm。在上过渡区（即，在高空无云空气附近）观察到从单峰到双峰（模式1直径为20 μm，模式2直径为10 μm）的液滴尺寸分布的变化。结果表明，这两种模式的液滴共存于相同的（小）空气体积和双峰形状的测量尺寸分布不能被解释为一个观察的工件所造成的积累数据点人口从不同的空气体积。第二尺度模态的形成可以解释为（a）新鲜气溶胶粒子的夹带和激活/凝结，或（B）云滴被卷入不同涡旋中时发生的不同蒸发过程。夹带粒子的激活似乎是一种可行的可能性，因为一层干燥的北极增强背景气溶胶（在层云正上方检测到）可能形成第二种模式的小云滴。然而，理论考虑和模型计算（采用直接数值模拟，DNS）显示，相反，湍流混合和蒸发较大的液滴是最有可能的原因形成的第二个液滴尺寸模式在最高区域的云。
Abstract. Aircraft borne optical in situ size distribution measurements were performed within Arctic boundary layer clouds with a special emphasis on the cloud top layer during the VERtical Distribution of Ice in Arctic clouds (VERDI) campaign in April and May 2012. An instrumented Basler BT-67 research aircraft operated out of Inuvik over the Mackenzie River delta and the Beaufort Sea in the Northwest Territories of Canada. Besides the cloud particle and hydrometeor size spectrometers the aircraft was equipped with instrumentation for aerosol, radiation and other parameters. Inside the cloud, droplet size distributions with monomodal shapes were observed for predominantly liquid-phase Arctic stratocumulus. With increasing altitude inside the cloud the droplet mean diameters grew from 10 to 20 μm. In the upper transition zone (i.e., adjacent to the cloud-free air aloft) changes from monomodal to bimodal droplet size distributions (Mode 1 with 20 μm and Mode 2 with 10 μm diameter) were observed. It is shown that droplets of both modes co-exist in the same (small) air volume and the bimodal shape of the measured size distributions cannot be explained as an observational artifact caused by accumulating data point populations from different air volumes. The formation of the second size mode can be explained by (a) entrainment and activation/condensation of fresh aerosol particles, or (b) by differential evaporation processes occurring with cloud droplets engulfed in different eddies. Activation of entrained particles seemed a viable possibility as a layer of dry Arctic enhanced background aerosol (which was detected directly above the stratus cloud) might form a second mode of small cloud droplets. However, theoretical considerations and model calculations (adopting direct numerical simulation, DNS) revealed that, instead, turbulent mixing and evaporation of larger droplets are the most likely reasons for the formation of the second droplet size mode in the uppermost region of the clouds.
用于云机载测量的在线数字全息成像系统的设计
影响因子：
1.9
作者：
Spuler
通讯作者：
Spuler
DOI：
10.1002/9783527653218
发表时间：
2013
期刊：
影响因子：
--
作者：
M.D. Andrés Hernández
通讯作者：
M.D. Andrés Hernández