河南省春季层状云系结构及其降水特征的研究

【作者】 廖菲；

【导师】 郑国光； 杜秉玉；

【作者基本信息】 南京气象学院 ， 大气物理学与大气环境， 2004， 硕士

【摘要】 本文对2002年4月4～5日和2003年3月30日～4月2日河南省两次春季层状云降水个例进行了分析。利用3小时一次的加密探空资料、卫星云图、雷达回波图、天气图、地面雨量、雨滴谱、微波辐射计等资料，分析了降水云系的宏观特征，并利用一维层状云模式研究了降水粒子的时空分布和水质粒形成的微物理特征，由此初步建立了河南省春季层状云降水的概念模型。 由观测资料分析可知，河南省春季层状云系结构不均匀，云系由若干个云块组成，云块之间有明显的界线，云顶高度在4～8km之间起伏变化，零度层亮带高度约为3.5km，云系存在一定厚度的过冷云层。暖区位势不稳定区位于0℃高度上下，冷区位势不稳定区位于-10～0℃高度之间。水汽含量最大值区位于700hPa附近，700hPa以下水汽通常来自南、东南方向，700hPa以上主要受西南气流影响。暖区700～500hPa之间一般存在上升气流。位势不稳定区所在高度的上方和下方会有风向切变和风速极大值中心，并且风切变或急流中心会早于位势不稳定的出现。暖区有明显的强降水中心，雨强极大值出现在山区迎风坡，降水雨滴谱谱宽较大，有时滴谱呈双峰型分布；冷区降水区常呈带状分布，雨区范围大，雨滴谱较窄，雨滴谱为单峰型。 一维层状云模式模拟结果表明，暖区以凝华增长的云水为主，云水分布在2～6km高度；雨水在云水形成后产生，分布在1～4km之间，主要通过碰并云水增长；霰在雨水形成后产生，主要通过碰并云水增长，分布在云水区的中下层，霰形成后，雨水主要由霰融化产生。冷区降水云以冰相粒子为主，冰晶由凝华过程产生，分布在6～8km的最高层；雪是降水云中含量最大的粒子，主要分布在2～6km之间，大部分雪通过凝华过程增长，少部分雪由碰并过冷云水生成；霰分布在1～3km之间，霰碰并雪及雪自动转化为霰是霰增长的主要方式，也有少部分霰由碰并过冷云水转化而来；绝大部分雨水由霰、雪融化形成，分布在霰累积区的下方，霰及雪的含量直接影响雨水的产生量。 通过对降水云系的综合研究，建立了河南省春季层状云降水概念模型：暖区降水主要通过云水碰并形成，冷区降水机制以冰粒子融化等冷云过程为主;暖区700一50OhPa通常有上升气流，冷区上升气流分布在近地面附近:700冲a存在风场的辐合，其上下则主要是辐散区;水汽主要集中在7O0hPa高度上，暖区水汽来自南、东南方向，冷区水汽以西南输送为主;暖区位势不稳定分布在O。C附近，冷区位势不稳定分布在一10一OOc，位势不稳定出现的时间与地面强降水、水汽最大累积区出现的时间一致。更多还原

【Abstract】 Two cases of spring stratus precipitation processes occurred during March 30 to April 2, 2003 and April 4 to 5, 2002 have been analyzed in this paper. The macro characteristics of status cloud systems have been studied by using every 3-hour sounding data, satellite cloud pictures, radar echoes, synoptic charts, surface rainfall, raindrop size distribution and microwave radiometer. The spatial distribution of precipitation particles and the mechanisms of their formation were studied by one-dimension stratus model. Thus, spring stratus precipitation conceptual model was primarily established in Henan Province.Analyzed results of macro observed data showed that the configurations of stratus cloud systems were inhomogeneous, and stratus cloud systems consisted of several single clouds. Different clouds were departed by obvious borderline, and the height of cloud top changed between 4 and 8km. The height of 0℃ level occurred at about 3.5km height which was meant that super-cold cloud existed. The temperature of potential instability area was about 0℃ in the warm area and between -10℃ and 0℃ in the cold area. Maximum vapor content existed at 700hPa level, and the vapor came from south or ease-south below 700hPa level and from west-south above 700hPa level. Positive vertical velocity existed between 700hPa and 500hPa. There were wind shear and maximum wind speed occurred above or below the height of potential instability area and one of them happened before potential instability. Heavy rainfall occurred in the warm area, and maximum rainfall lay in the windward slope where the width of raindrop size distribution was broadened and sometimes it was bimodal spectrum. The shape of rain band in cold area was zonal, and the area of rain band was small. The width of raindrop size distribution in the warm area was narrow and its shape was single model.Simulating results of one-dimension stratus model showed that the content of cloud water that grew up by deposition process was the largest in the warm area, andcloud water existed between 2km and 6km. In the warm area, the formation of rain water which existed between 1km and 4km was behind of the formation of cloud water, and the development of rainwater was depend on collecting cloud water. The occurrence of graupel that grew up by the means of collecting cloud water was behind of rain formation, and existed in the lower layer of cloud water. In the cold area, ice phase particles were the main particles in the cloud. Ice crystals were formed by means of deposition process and existed at the top position from 6 to 8km. Snow content was highest in the cloud and existed between 2 and 6km. Snow grew up by deposition primarily and by collecting super cold cloud water secondly. Graupel that grew up primarily by collecting ice crystal existed between 1 and 3km. Collecting cloud water and snow auto conversion were the mainly ways of graupel development.Through synthetic analysis of stratus cloud systems, stratus precipitation concept model has been primarily established. It was well known that the main process of precipitation formation was collecting cloud water in the warm area and ice phase particles melting in the cold area. Positive vertical velocity existed between 700hPa and 500hPa in the warm area and near surface in the cold area. Wind convergence existed at the height of 700hPa, and divergence existed above and below the height of 700hPa. Maximum vapoT content intensified at 700hPa level. Vapor came from south or east-south in the warm area and from south-west in the cold area. Potential instability existed near 0℃ in the warm area and between -10℃ and 0℃ in the cold area. The occurrence of potential instability was corresponding with maximum rainfall and maximum vapor content.更多还原