【作者】 居丽玲；

【导师】 牛生杰； 段英；

【作者基本信息】 南京信息工程大学 ， 大气物理学与大气环境， 2012， 博士

【摘要】 为了抗旱减灾、缓解水资源短缺、保障国家粮食安全,河北省每年的春秋两季均开展飞机人工增雨作业。在作业的同时利用机载粒子测量系统PMS进行云物理探测,研究云系结构和降水形成机制,从而提高人工增雨的科学性、针对性和有效性。本文利用2005-2009年河北省春秋季常规天气资料、非常规气象资料以及机载PMS探测资料,采用天气学和云物理学相结合的方法,研究了河北省春秋季层状降水云系的宏观结构、云与降水的微物理特征,探讨了云系的可播性条件；通过典型个例综合观测分析和数值模拟,揭示了降水形成的物理机制,丰富了对河北地区层状降水云系物理特性的认识。得到如下主要结论：1.河北省春秋季层状降水云系的宏观特征。影响河北省春秋季并可产生降水的天气系统主要有低槽、冷锋、低涡、气旋、切变线、回流等,其中低槽、冷锋是主要影响系统。不同天气系统在春秋两季对降水量的贡献不同。大范围层状云系内部具有非均匀性结构特征,造成地面降水的不均匀分布。大部分的水汽含量集中在大气中低层,500hPa以下水汽占了整层水汽含量的93%-98%以上。层状云降水天气绝大多数为热力稳定型但同时存在位势不稳定区,并存在弱的垂直上升速度。2.河北省春秋季层状降水云系的微物理特征。河北省2005-2009年春秋季层状降水云系云粒子浓度14～205个/cm3,平均直径7～18μm,King探头实测云中平均液态水含量0.26 g/m3,最大1.636g/m3,平均冰晶浓度为27.7个/L。春季云粒子浓度、云滴含水量、平均直径比秋季大。冷锋过境前后,云微物理要素差异较大。在冷锋过境前平均云滴浓度相对较大,粒子直径偏小,云水含量相对较低；云系发展旺盛或成熟期,云滴浓度下降明显,粒子直径普遍增大,冰晶粒子数量增加；冷锋过境后,云滴浓度进一步下降,云粒子直径和云水含量继续增大,冰晶粒子数量和冰晶直径都减小。冷锋过境前后,As云和Sc云内,云微物理量要素变化显著,但云粒子谱变化不大。3.河北省春秋季云系的可播性条件。观测研究表明,河北省2005-2009年春、秋季层状降水云系大多具有多层结构,符合“催化云—供水云”结构,有利于降水的云层结构是下层配合Ns或Sc的Asop云占55.7%。降水性层状云系过冷层厚度平均1414m,符合可播性条件。降水云系过冷层含水量丰富,87%的架次观测到含水量大于0.1 g/m3的过冷水区。King探头实测平均为0.16g/m3,春季略高于秋季；过冷水含量随云系的不同发展阶段、不同部位有很大差异,而不同降水云型其过冷水含量也有很大不同。云滴最大浓度大多在21～216个/cm3之间。降水云层的冰晶浓度较低,冰晶浓度小于27.7个/L的占到55%,具有较大的人工引晶催化潜力,播撒层基本上在-2～-8℃。4.揭示了降水形成的物理机制。选取2008年10月4日～5日河北省出现的一次典型冷锋层状云降水过程进行观测和数值模拟分析。研究表明,冷锋云系符合“催化—供给”机制。云内高层是冰晶,中层是雪,接下来是霰和过冷云水组成的冰水混合层,最下方是暖水层。供水云为锋下层积云,有云滴、雨滴和从上层降落下来以后融化的雪和霰,紧接着靠液滴间碰并增长形成降水粒子。催化云为锋上高层云,是由冰晶、雪、霰和过冷云水组成的冰水混合云,冰晶和雪的增长不仅有冰晶的凝华和聚合过程,还包含雪晶凇附过冷水和攀附过程,卷层云中的冰晶对高层云起着自然催化作用。降水云系冷云过程与暖云过程共存,降水主要以冷云过程发动。降水发展的不同时段,云内结构、各种湿物质之间的转化关系和雨水形成机制都存在明显差异。更多还原

【Abstract】 For relieving drought, easing the shortage of water resources, protecting national food security, Hebei carried out aircraft artificial precipitation enhancement in annual spring and autumn. At the same time the cloud physics data was detected by the airborne Particle Measuring systems (PMS) in order to study the structure of the cloud system and the formation mechanism of precipitation, improve the scientificalness, and pertinence and availability of artificial precipitation. In this paper, based on the conventional sounding data, non-conventional observation and detection data of airborne PMS system, and using a combination of methods of synoptic systems and cloud physics, we make an analysis of the macro-structure of stratiform cloud in spring and autumn in Hebei, the microphysical characteristics of precipitable stratiform clouds, and discusses the conditions of the cloud system that can be seeded, reveal the physical mechanism of precipitation formation through the observation and analysis of the typical case and numerical simulation, enrich the understanding of the physical characteristics of the cloud system in Hebei, The main results are as follows.1. The macrophysics characteristics of stratiform cloud of spring and autumn in Hebei province. There are several categories of weather systems, including the low trough (inverted trough), cold front, vortex, cyclones, shear line and return flow lead to precipitation in spring and autumn, Hebei Province. The low trough and cold front are the major influence systems. Different weather systems in spring and autumn give the different contribution of precipitation. Inhomogeneity internal structure in a wide range stratiform cloud is corresponding to the uneven distribution of ground precipitation. Most of the water vapor is concentrated in the mid and low layers. The water vapor under 500hPa makes up 93%～98% of the whole layer. Most of stratiform cloud precipitation systems are thermal stable types, and exist potential instability regions and weak vertical velocity.2. The microphysics characteristic of precipitable stratiform clouds in spring and autumn, Hebei Province. Statisticsed the microphysics characteristic of precipitable stratiform clouds in spring and autumn during 2005-2009, Hebei Province, cloud droplet concentration range from 14 to 205 cm-3, average diameter range from 7 to 18μm. Observed by King Probe, average LWC is 0.26 g/m3, the max value is 1.636 g/m3, average ice crystal concentration is 27.7/L. The value of number concentration, average diameter and LWC is higher in spring than those in autumn. During the pre and post of cold front passing over, the cloud microphysics appears significant different. Pre-cold front passing, the observed cloud number concentration is relatively high, and both the droplet diameter and cloud water content are low in the early stage of cloud system development. During the mature stage, the cloud concentration decreases obviously, the diameter and the number of ice particles increase. When the cloud front have passed over, cloud concentration will decrease continually in the rear of cloud system; and the number of ice particles and diameter of ice particles will decrease, but cloud droplet diameter and cloud water content will increase continually, both size and diameter of ice crystal will decrease. When the pre and post of cold front passing over, the cloud microphysics has significant variation, while the cloud spectrum will not change much in the As cloud and Sc cloud.3. The seedability condition of cloud system of spring and autumn in Hebei province. There is multi-layer structure in the precipitable stratiform cloud system during spring and autumn in Hebei province, the distribution of cloud is corresponding with "catalysis-supply cloud" structure. The clouds structures are in favor of precipitation are Asop cloud with Ns or Sc in low layer which make up 55.7%. The average thickness of super-cooled layer is 1414 m which is suitable for artificially seeding. Observations show that supercooled LWC is quite rich,87% of the sorties is greater than 0.1 g/m3 and potential rainfall. The average is 0.16 g/m3 from King, the spring slightly higher than the autumn. The supercooled water content of cloud is very different, with the different stages or parts of development of the cloud system, and different precipitation cloud type. The maximum cloud droplets concentrations are between 21 and 216cm-3. Ice concentration is low in precipitation clouds, more than 55% ice concentration lower 27.7/L, with a large catalytic ability of artificial seeding. The seeding layer temperature is between -2 and -8℃.4. The physical mechanism of precipitation formation. The typical cold front precipitation process happened from 4 to 5 in October,2008 is chosen to observe and numerical simulation analyze. The results show that the cold front is in accord with the "catalysis-supply" mechanism. The ice crystal is in the high layer of cloud, the snow is in the mid-layer of cloud, and graupel, supercooled cloud water is in the next layer of cloud, and the liquid water layer in the water region of cloud is in the low lay of cloud. The stratocumulus cloud under the front is water supply cloud, and there are cloud droplets, rain droplets, and snow and graupel felling from the upper layer after melting. The collision and coalescence of the liquid droplets make the main contribution to the form of rain droplets. The stratocumulus cloud over the front is catalysis cloud, consisting of ice crystal, snow, graupel and ice-water mixed clouds of supercooled cloud water. The increase of ice crystal and snow include not only sublimation and aggregation process, but also the riming and cluming process of snow crystals. The ice crystals in cirrostratus cloud affect the natural catalysis. The cold-cloud process and warm-cloud process coexist in precipitation system. The precipitation be started mainly by cold-cloud process. The cloud structure, the transformation between a variety of wet material and the formation mechanism of rain are significantly different in precipitation cloud system simulated.更多还原