【作者】 王黎俊；

【导师】 银燕；

【作者基本信息】 南京信息工程大学 ， 大气物理学与大气环境， 2013， 博士

【摘要】 受冷锋天气系统影响产生的多层层状云系,是三江源地区秋季的主要降水云系,也是人工增雨的主要作业对象。本文利用第一次三江源地区飞机观测试验期间的机载粒子测量系统(Particle Measuring Systems,简称PMS)资料,通过垂直微物理结构特征、各高度层云粒子相态的综合判定和粒子谱分布的分析,系统研究了该地区秋季一次多层层状云系的微物理特性,探讨了云粒子增长机制；通过飞机播撒AgI焰剂水平输送的分析,在确定作业前后有效对比区间的基础上,分析作业前后液态云粒子及冰晶浓度变化、云粒子谱的演变和过冷水含量比率的变化,研究了层积云催化的微物理响应,为该地区人工增雨定量化科学指标的判定和效果检验提供了微物理依据。主要结论如下：(1)秋季多层层状云系(Cs-As-Sc)的垂直结构和微物理特征：云系在发展阶段分为4层,云层之间均有干层存在。其中,Cs和上层As为冰云,下层As和Sc为冰水共存的过冷混合态云,过冷水含量较丰富。云系中,云粒子浓度和过冷水含量在下层As底部最大；粒径D>50μm云粒子的浓度平均值由最顶层的Cs向下依次递减,直径平均值依次递增；云粒子尺寸及谱宽在最底层的Sc中最大。与中国北方其它地区类似云层的比较结果表明,As和Sc的云粒子浓度均偏大,As的液态含水量计算值LWCFSSP偏高,Sc云粒子谱宽偏宽,具有较为明显的地区特征。混合态云中,FSSP(前向散射粒子谱探头)所测的云粒子浓度对数值与直径有着明显的反相关性,高浓度区对应高含水量区。高过冷水区和低过冷水区的云粒子谱分布差异明显,其中Sc高过冷水区存在比较明显的淞附增长现象。(2)根据2DC(二维灰度云粒子探头)图像和灰度投影资料判定了混合态云中2DC量程内粒D>50μm云粒子的相态；综合FSSP云粒子瞬时谱、FSSP所测一定尺度云粒子含水量值与King探头过冷水含量实测值的对称相关性,区分了混合态云中FSSP量程内云粒子的相态。结果认为：Sc(下层As及对流泡)中中值直径在3.5～18.5μm (3.5～21.5μm)之间的云粒子基本上为液相,中值直径大于21.5μm(24.5μm)的云粒子基本上为冰相。混合态云中,Sc-下层As云底-对流泡顶,高过冷水区的云滴有效半径随着高度增加而依次增加。高过冷水区的过冷水含量比率在Sc中与过冷水含量存在一定的关联性,而在下层As云底无明显变化,其均值及标准差在Sc中为69.9±19.4%,在下层As云底为89.2±8.1%。(3)各高度层粒子谱分布特征分析和云粒子增长机制的探讨。混合态云各高度层FSSP平均粒子谱分布的谱型均为单峰型伽玛分布,混合态云和冰云2DC平均粒子谱基本上为负指数型分布,具有较为明显的地区特性。在冰云和下层As中,冰晶的增长可能仅限于凝华增长和冰晶之间的碰并增长,这种增长机制可能很难产生超过400μm的大冰相粒子。下层As中,冰晶凝华增长所需的水汽不仅来自云内的冰水转化,而且还来自于上升气流输送的外来水汽的补充。较强的上升气流有利于云滴谱宽拓宽、浓度增大。(4)催化试验观测发现,锯齿型作业后约2-23min,在其航线下风方36km范围内,FSSP和2DC所测云粒子浓度、直径变化均未超出作业前云区内的自然起伏,但在过冷水含量大于0.01g/m3的高过冷水区,液态云粒子浓度明显减少,FSSP量程内的冰晶粒子浓度明显增加,冰相含水量增大,过冷水含量比率的平均值由作业前的68.3±23.1%减小至34.2±12.4%。在过冷水含量越高的区域,催化效应越明显,而在低过冷水区和仅受原点催化影响的航迹交叉点处均未出现催化响应。更多还原

【Abstract】 Multi-layer stratiform clouds system generated by cold front weather system is the main precipitation cloud system at Sanjiangyuan National Nature Reserve in autumn and is the job object of artificial rainfall. Making use of data of PMS (Particle Measuring Systems) data observed during the airborne observation experiment over the Sanjiangyuan National Nature Reserve, the structure of microphysical feature in vertical layers, the phase of cloud particles at different heights and the distribution of particle spectrum, the microphysical characteristics of the multi-layer stratiform clouds in autumn are studied. In the meantime,the growth mechanism of cloud particles is discussed. By analyzing the horizontal transport of aircraft sowing the AgI flame agent, microphysical effects are studied, First, the effective area before and after the operation are compared and got the distinguishing of cloud particle’s phase state, then the variation of total number concentration of liquid cloud particles and ice crystal,cloud particle spectrum and f1(fraction of liquid water) are analyzed. This results can provide a microphysical theoretical basis for quantitative index of the artificial rainfall and effect of test in this region. The main results are as follows.(1) The vertical structure and microphysical characteristics of autumn multi-layer stratiform clouds system (Cs-As-Sc) are analyzed in this paper. The clouds system of development consists of four layers. The Cs(cirrostratus) and the upper-level of As(altostratus) are ice-phase cloud, while the lower level of As and Sc(stratocumulus) are supercooled mixed-phase cloud. The particle concentration and the supercooled water content of the lower level As are the largest in the cloud system. The average particle concentration which the radius larger than50μm is gradually increased from the top of Cs down. The Cs particle size and spectral width of the lowest layers are the largest in the cloud system, which has a clear regional characteristics. Ous results was compared with the observation analysis of other area in northern China. It is found that:the value of LWCFSSP (Liquid Water Content by Forward Scattering Spectrometer Probe)and particle concentration of As and Sc are larger is our observation; besides, the breadth of cloud particle spectrum are wider. The particle concentration which observed by FSSP(Forward Scattering Spectrometer Probe) had remarkable negative correlation with its diameters and the area of high concentration corresponds to high moisture content. The difference between the high and the lower supercooled water in the cloud particles spectrum are distinguished. The high supercooled water area of Sc has an obvious rime growth phenomenon.(2) According to the2DC(Two-Dimensional Cloud Probe) image and gray projection data, the phase of particle radius D large than50μm is judged in this paper. In the meantime, based on the correlations about the instantaneous spectrum of FSSP cloud particle, the value of liquid water content calculated from FSSP and the observation of supercooled water content obverted with King detector, the particle phase in the mixed-phase cloud are also judged. The median diameter of cloud particles between3.5～18.5μm (3.5～21.5μm) in the Sc (lower As and convective bubble) is liquid phase while median diameter of cloud particles greater than21.5μm (24.5μm) is ice phase. The droplets effective radius of high supercooled water area increased with the increasing cloud height in the bottom of Sc and As. The supercooled water content mean ratio of the high subcooled water area are related to the supercooled water content in Sc while it is opposited in lower As of cloud.(3) The features of particles spectrum at different heights are analyzed and the growth mechanism of cloud particles is discussed. The cloud particle spectrum in the mixed-phase cloud observed by the FSSP and observed by the2DC are respectively in single-peak Γ distribution and in the negative exponential distribution. In ice cloud and lower layer As, the growth of ice crystal may be limited to growth of condensation and coagulation, which make it is difficult to generate ice phase particles larger than400μm. At lower layer As, the vapor needed in condensation is not only from the ice-water transformation occurred in cloud, but also from the updraft which can transport vapor from outside. Strong updraft can be an advantage for broadening cloud particle spectrum and increasing concentration.(4) At the leeword of routine in the scope of36km about2-23min later after seeding, the variation of concentration and diameter detected by FSSP&2DC in test region, which is not out of the range of normal floating compared with pre-test. However, in the high supercooled water area(HSWA) where the SLWC(supercooled liquid water content) larger than0.01g/m3, the concentration of cloud particles for liquid phase decrease obviously and the density of ice crystal particles increased. The mean value of f1reduced from68.3±23.1%to34.2±12.4%. The effects of seeding is remarkably in high supercooled water area, but not obviously in low supercooled water area and routine cross points which just influenced by original seeding that effects in comparison.更多还原