三江源地区秋季典型多层层状云系的飞机观测分析

利用三江源地区一次机载粒子测量系统PMS(Particle Measuring Systems)的分层垂直探测资料,系统研究了该地区秋季典型多层层状云系的微物理特性,结果表明:(1)云系由4层云层组成,Cs(卷层云)和上层As(高层云)为冰云,下层As和Sc(层积云)为过冷混合态云。下层As的云粒子浓度和过冷水含量最大,Sc的云粒子尺寸及谱宽最大,且具有较明显的地区特性;(2)Sc(下层As及对流泡)中中值直径在3.5～18.5 μm(3.5～ 21.5 μm)之间的云粒子为液相,中值直径大于21.5 μm(24.5 μm)的云粒子为冰相;(3)混合态云中高过冷水区与低过冷水区云的粒子谱分布差异明显,Sc高过冷水区有较明显的淞附增长现象;(4)Sc、下层As云底、对流泡顶高过冷水区的云滴有效半径依次增加。Sc高过冷水区的过冷水含量比率均值及标准差为69.9±19.4%,且与过冷水含量存在一定的关联性;下层As云底高过冷水区的过冷水含量比率无明显变化,其均值及标准差为89.2±8.1%;(5)混合态云各高度层FSSP(前向散射粒子谱探头)平均粒子谱均为单峰型伽玛分布,混合态云和冰云各高度层2DC(二维灰度云粒子探头)平均粒子谱基本上都为负指数型分布。

Analyses on Typical Autumn Multi-Layer Stratiform Clouds over the Sanjiangyuan National Nature Reserve with Airborne Observations

The microphysical characteristics of multi-layer stratiform clouds in autumn are examined using layered vertical observation data of Particle Measuring Systems (PMS) obtained during an airborne observation experiment over the Sanjiangyuan National Nature Reserve. Results show that cirrostratus (Cs) and upper-level altostratus (As) are ice-phase clouds, while lower-level As and stratocumulus (Sc) are supercooled mixed-phase clouds. The particle concentration and the content of supercooled water of the lower level As are the largest in the cloud system. The Sc particle size and spectral width are the largest and shows clear regional characteristics. The median diameters of the Sc (lower As and convective bubble) cloud particles are 3.5-18.5 μm (3.5-21.5 μm) for the liquid phase and greater than 21.5 μm (24.5 μm) for the ice phase. The differences between the higher and lower supercooled water in the cloud particle spectra are distinguished. The high supercooled water area of Sc exhibits an obvious rime growth phenomenon. The effective radius of droplets becomes increasing large in Sc, at the bottom of the lower-level As, and on the top of the convective bubble. The content of supercooled water of the high subcooled water area has a mean ratio and standard deviation of 69.9±19.4%. In addition, the fraction of liquid water in Sc is related to the supercooled liquid water content in the high content of water, but there is no obvious variation in the lower-level As, which shows a mean ratio and standard deviation of 89.2±8.1%. The cloud particle spectrum in the mixed-phase cloud observed by the Forward Scattering Spectrometer Probe (FSSP) and the Two-Dimensional Cloud Probe (2DC) are respectively in single-peak Γ and negative exponential distribution.