【作者】 覃文娜；

【导师】 包云轩； 高苹；

【作者基本信息】 南京信息工程大学 ， 应用气象学， 2012， 硕士

【摘要】 冰雹灾害是由强对流天气系统引起的一种局地性强、季节性明显、具有突发性和阵性特征的气象灾害。一次范围较大、强度较强的降雹,往往伴随着各种阵发性极端灾害性天气过程,如狂风、暴雨、急剧降温等。冰雹是江苏省重要的灾害性天气之一,虽然发生范围小、时间短促,但来势迅猛、强度大,并常伴随狂风、暴雨,易给局部地区造成重大损失。由于冰雹多出现在农作物生长的关键期,十几分钟的降雹即可使农作物遭受毁灭性损害,甚至威胁到人民生命财产。因此,分析江苏省历史上冰雹发生时空变化规律、产生天气背景及主要气候特征的基础上,应用WRF模式对一些冰雹天气过程进行数值模拟试验,结合多普勒天气雷达提供的相关冰雹回波信息,揭示其成因,探明下垫面因素对冰雹产生的影响,并通过对个例模拟输出结果的统计分析,寻找冰雹发生的监测预警参数和预报指标,以提高冰雹天气预报的准确率和精确度,同时为相关部门指导防灾减灾工作提供科学依据。本研究根据江苏省70个气象台站1980～2009年间的冰雹观测资料,分析了江苏省冰雹灾害发生的时空变化特征,并结合Mann-Kendall方法探讨了气候变暖对江苏省冰雹发生趋势的影响。研究表明：(1)江苏省上世纪80年代为降雹多发期,90年代明显减少,本世纪初以来又有明显回升趋势。(2)江苏省一年中降雹多发季为春、夏两季,降雹日约占全年总降雹日数的94.7%；一年中降雹最集中的月份为4-8月,沿海和淮北地区6月最多、5月次之,苏南、苏中地区5月最多,6月次之,冬季的3个月(12月～次年2月)为降雹最少的季节。(3)全省降雹空间分布的总体特征是：东部沿海多,西部内陆少；中北部多,南部少；里下河地区的兴化市和东部沿海的射阳县是全省降雹最多的地区,西南部的宁镇扬丘陵地区是全省降雹最少的地区。(4)这30a中发生在江苏省的降雹路径主要有四条：第一条从山东的沂南、营南经江苏的赣榆、连云港、灌云、灌南、响水、滨海到达阜宁(或涟水)一线；第二条从山东的微山湖沿大运河南下,经江苏的邳州、睢宁到达宿迁一线；第三条从江苏省内的东台向南经海安、如皋、靖江到达江阴一线；第四条从省内的无锡向东南经苏州到达昆山一线。(5)与江苏省冰雹灾情年际不稳定度成正相关的雹日空间变异系数自东北向西南递增。(6)导致这30a江苏省冰雹时空变化格局的主要成因是全球气候变暖、大气环流背景、局地中小尺度大气动力场、地形起伏和下垫面热力属性等。基于中尺度数值预报模式WRFV3,利用NCEP1°×1°再分析资料、常规气象观测资料及多普勒雷达资料,选取2009年6月5日发生在江苏地区一次冰雹天气过程进行了数值模拟。对模式输出的物理量进行诊断分析后发现：(1)此次强对流天气过程是在东北冷涡持续稳定少动,涡后弱冷空气南下和地面处于冷锋前增温增湿的大环流背景下产生的；(2)多普勒雷达回波组合反射率在55dBz以上、出现正负速度对及中气旋、垂直累积液态水含量在55kg·m-2以上、回波顶高在9km以上,验证这次冰雹过程的产生和发展,在强对流天气的潜势预报中有着重要的指导意义。(3)江苏东部沿海低层水汽辐合带源源不断的水汽输送和辐合,为冰雹的形成提供了较好的水汽条件,同时使得降雹区上空存在上干下湿的层结状况,700hpa附近形成一个干区,中低层的干暖空气促使这次强风暴的发展。(4)降雹前,江苏省东部形成一条大于1600J·kg-1的高能带,与雷达强回波带相对应,加上露点锋、海风锋等地面辐合系统及较强的垂直上升运动,为冰雹的发展提供足够的热力条件和动力条件。(5)0℃层高度在3.5～4km、-20℃层高度在5.5～6.0km是此次过程适宜冰雹增长的高度,0℃和-20℃两层厚度在180～220hPa之间,暖云层与冷云层的厚度比在1：2～1：5之间,也是此次冰雹生长的合适条件。考虑下垫面因素的影响,利用WRF模式对2009年6月5日出现的冰雹天气过程模拟效果进行了一系列敏感性试验,结果表明：下垫面性质、地形不一样导致热力非均匀,通过影响低层风、温、湿等气象因素,进而影响冰雹等强对流天气。水体对局地有降温作用,同时使得上空湿度增大,而且对风向风速有一定阻滞作用；丘陵、平原和沿海滩涂对其上大气的温度、湿度等要素的影响各不相同,对局地环流有加强或减缓作用。更多还原

【Abstract】 The hail damage is a meteorological disaster caused by the strong convective weather systems, which has characteristics of obvious seasonal and paroxysmal. A large range of severe hailstorm often accompanied by paroxysmal extreme disastrous weathers process, such as strong winds, heavy rain, plunged temperature and so on. Hail is one of the most important extreme weather in Jiangsu Province. Although it occurs within narrow zones and shorter in duration, it is fast, violent, intensity and often along with strong winds, heavy rain.which cause serious damage to human-made structures and, most commonly, farmers’ crops. Therefore, this becomes particularly important for us to do analysis of hail temporal and spatial variation, weather background and the main climatic characteristics in Jiangsu Province. This paper used WRF model to simulate a number of hail, combined with information provided by Doppler weather Radar, to reveal the causes of hail and the impact of the underlying surface to hail, and through statistical analysis of simulation output of hail cases, to find early warning parameters and forecast indicators of the hail, in order to improve the forecast accuracy of hail, as well as provide a scientific basis for government to guide disaster prevention and reductionBased on the observed hail data of70meteorological stations in Jiangsu province during1980to2009, in this study, the temporal and spatial distribution characteristics of hails were analyzed. Mann-Kendall method, a tool of detecting the extraordinary climate variations, was used to discuss the influence of the climate warming on the occurrence tendency of hail disasters in Jiangsu. The results were showed as follows:(1) the inter-decades variations of hail disasters in the whole province were that the highest frequency period of hailing occurred in1980s of the last century, the hailing days per year in1990s reduced obviously, but it had a remarkable raising tendency since2000.(2) The main occurring seasons of hail in Jiangsu Province were spring and summer and their hailing days accounted for94.7per cent of the total hailing days in a year. The concentrated hailing months in a year was April, May, June, July and August. Among them, the month of maximum hailing days was June and the second frequency month was May in the coast regions and the northern side of the Huai River Valley of the province, but the maximum frequency month of hailing was May, the next was June in the other regions. December, January and February in winter has been the rare hailing months of a year.(3)The spatial pattern of hailing in the province was that the hailing days in the eastern coast regions of the province is more than the western inland regions, the hailing days in the middle and north part was more than the south part, Xinhua City in the Lixia River Region and Sheyang along the coast of the Yellow Sea were the high frequency areas of hailing days in the whole province and the Nanjing-Zhengjiang Hilly Region was the lowest frequency area of hails.(4)In recent30years, the hail has four main routes in the province.(5)The spatial variance coefficient of hailing days increased progressively from the northeastern part to the southwestern part in the province.(6) The main mechanisms resulted into this spatio-temporal change situation of hails in the province were the global climate warming, the backgrounds of atmospheric circulation, the local atmospheric dynamic fields, the landforms undulation and the thermodynamics attributes of the surface.Based on mesoscale numerical prediction models WRFV3.1, using the NCEP1°×1°reanalysis data, the routine meteorological observation data and Doppler Radar data, the hail occurred in June5,2009in the Jiangsu was simulated. By diagnostic analysis of the physical quantities of the model output, found that:(1) the strong convective weather produced in the weather ground which northeast cold vortex is a steady move, weak cold air south after vortex and the ground is warmer and humidifier before the cold front;(2) The CR is above55dBz, appears the positive and negative speed or the cyclone, VIL is more than55kg·m-2, and the echo top is above9km, etc in Doppler Radar. These verified the generation process of hail. There are important guiding significance in potential forecasting for the severe convective weather.(3) In the eastern coastal of Jiangsu Province a steady stream of water vapor transport and moisture convergence from convergence zone in low-level, provided moisture conditions for the formation of hail. While hail district exists the under wet on dry stratification conditions.It has dry area near700hpa, dry and warm air in the lower promotes the development of the strong storm.(4) Before the hail, in eastern of Jiangsu Province, It has a greater than1600J·kg-1high-energy band, corresponding to radar echo zone. The surface convergence systems as dew point front, the sea breeze front and strongly vertical upward motion provide adequate thermal conditions and dynamic conditions for the development of the hail.(5)0℃layer height is3.5-4km,-20℃layer height is5.5-6.0km, which are suitable for hail growth. Thickness between0℃and-20℃C layers is180to220hPa, the thickness ratio of warm clouds and cold clouds is1:2to1:5are also suitable conditions for hail growth.Considering the underlying surface factors, this paper used WRF Model simulate the process of hail on June5th,2009and carried out a series of sensitivity tests, the results showed that:the different underlying surface and terrain caused non-uniform heat. It through affected low-level wind, temperature, wet weather factors to influence the hail and other severe convective weather. Water body can cooling local temperature, while increased the humidity over the water body, block to the wind.Hills and plains, coastal differently effect temperature, humidity etc. Otherwise it also enhanced or reduced local circulation更多还原