【作者】 常平；

【导师】 周兵； 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2010， 硕士

【摘要】 德州市位于北纬36°24’-38°0’、东经115°45’-117°24’之间,黄河下游北岸,山东省西北部。地势平坦,海拔高度20米左右,西距太行山脉约200km,东南部为鲁中山区。鲁西北平原地区是山东省强对流天气高发区,是省内仅次于鲁中山区的冰雹多发地,强对流天气几乎每年都会给鲁西北带来冰雹和大风灾害,造成严重损失。本文首先分析了鲁西北强对流天气气候的时空分布特征,并与省内其他地区进行了比较,鲁西北强对流天气的分布有明显的季节性和区域性特征,是省内强对流多发区之一,其季节分布与全省基本一致,但与省内其他区域强对流的月度分布上有所差异。以德州市1979～2006年71个冰雹天气个例为研究对象,利用1.25°×1.25°GMT 00、06、12、18四个时次日本气象厅JRA25再分析资料,对影响鲁西北强对流过程的天气系统进行了普查归类,将影响鲁西北强对流的天气系统分为四类：低涡、低槽、横槽、西北气流,低涡类降雹占总数的56.3%,低槽16.9%,西北气流15.5%,横槽11.3%。并选取样本对每种天气型式强对流过程进行了合成分析,归纳了其典型天气背景特征模型,并对中低层配置情况进行了讨论。根据强对流产生的物理机制,选取了多种强对流参数进行了诊断分析,热力对流参数K指数、抬升指数LI、沙氏指数SI、总温度指数TT、对流有效位能CAPE,动力参数0～1km、0～3km、0～6km风切变SHR、风暴相对螺旋度SRH,动力和热力综合指数强天气威胁指数SWEAT、风暴强度指数SSI、能量螺旋度EHI,以及0℃层高度ZHT与-20℃层高度ZHT20等多种对流物理参数是判定鲁西北地区大气是否处于对流性不稳定及冰雹能否生成的重要因子,部分参数与国内外其他地区使用阀值有一定区别。针对2006年7月5日的强对流天气过程,进行了天气背景以及多种物理因子的诊断分析,结果表明：受高空冷涡的影响,中高层冷空气的入侵,触发不稳定能量释放造成了此次强对流天气发生。由稳定度和环境风场分析可知,强对流发生前12小时,低层850hPa以下渤海西部的偏东风向本区输送水汽,造成本区附近上空低层水汽饱和度较高,中高层干冷空气入侵导致大气不稳定度逐渐增加,这种低层湿,中高层干的大气层结特点,非常有利于冰雹生成发展。计算K指数等强对流参数的分析发现,本区附近上空大气具有较明显的不稳定层结特征,对对流天气的发生区域有较好指示作用,动力参数0～3km垂直风切变SHR、风暴相对螺旋度SRH,对实际冰雹等强对流发生区域具有明显指示意义,表明风切变是决定风暴组织结构和强弱风暴的关键因子。卫星云图分析表明,鲁西北强对流发生时云顶温度TBB在-40℃至-55℃,强对流最剧烈冰雹、大风天气主要发生在雷暴云团前方亮温梯度最大区域内。多普勒雷达回波分析表明,造成此次鲁西北强对流天气的回波主要是弓状回波上的超级单体风暴和多单体风暴,中心强度均在55dbz以上,最大达65dbz,其中弓状回波顶端的超级单体风暴造成的天气最剧烈,灾害最严重,其低层存在中气旋,低层径向速度与地面风速正相关；降雹区垂直积分液态含水量VIL在50 kgm-2以上,VIL产品与降雹相关性很好,其值对冰雹的存在有较好的指示作用。更多还原

【Abstract】 Dezhou City locates at 36°24′-38°0′N,115°45’-117°24′E, the north shore of the lower Yellow River, lying in north-west Shandong Province. The region is covered by plains with altitude 20 meters or so, about 200km apart from Taihang Mountains in the west. There is a high incidence of severe convective weather in northwest Shandong, which is second only to the central mountainous areas in Shandong Province. Severe convective weather happens frequently almost every year to bring hail and high winds disasters causing serious damage in the area. In the thesis we first analyze the temporal and spatial distribution characters of climate of severe convective weather in northwest Shandong, with compared to other regions in the province. The distribution of severe convective weather has an obvious seasonal and territorial characteristics in the northwest Shandong, which is one of the most prone areas of severe convection in the province, basically same as the province, but different in the monthly distribution of severe convection from other regions.Based on the 71 severe convective weather cases in Dezhou City from 1979 to 2006, using JMA JRA25 1.25°×1.25°reanalysis data on GMT 00,06,12,18, we classify the severe convective weather background according to the synoptic system leading to severe convection and get four categories:low vortex, upper-level trough, transverse trough, northwest flow, low vortex type hail accounted for 56.3% of the total, upper-level trough 16.9%, northwest flow 15.5%, transverse trough 11.3%. Synthesized analysis for each type of severe convective weather by selecting the samples is put up to summarize the background of the typical characteristics of different weather model, with the configuration between middle-level and low-level being discussed. According to the physical generating mechanism of severe convection, the diagnostic analysis of a variety of strong convection parameters are carried out, thermal convection parameter K index, uplift index LI, showalter index SI, the total temperature index TT, CAPE, dynamic parameters 0～1km、0～3km、0～6km wind shear SHR, the storm relative helicity SRH, dynamic and thermal composite index severe weather threat index SWEAT, storm intensity index SSI, energy helicity EHI, as well as the 0℃layer height ZHT and -20℃layer height ZHT20, these variety of physical parameters of convection is useful to determine instability of the atmosphere and the possibility of hail in the northwest Shandong, with some parameters having a certain difference threshold used in other parts at home and abroad.In this paper, aiming at the severe convective weather on July 5,2006, we had analyzed the weather background, detailed physical actors and diagnostic analysis of physical quantity. The results show that:the impact of cold vortex, high-level cold air intrusion, which may trigger instability in the energy release, is caused the main reason for the severe convective weather. By the stability and environmental wind field analysis it shows that when the severe convection occurs 12 hours before, there is the east wind under the 850hPa level, which plays a important role in transporting water vapor from the west of the Bohai Bay, resulting in increasing the humidity and tending to saturate the atmosphere in this area. The characteristics of the atmosphere stratification which structure is moist in low-level with dry in the upper-level are consistent with the conditions where hails happen often. By calculating lots of parameters of severe convection it shows that the air over this area is unstable, which can indicate well where the convective weather occurs. The high-value center of dynamic parameters 0-3 km SHR and SRH is magnificently consistent with the place where the hail and gale break out, which indicates that wind vertical shear is the key factor to determine the organizational structure and strength of thunderstorms. The analysis of Fy-2c Satellite infrared cloud-images indicates that the TBB of cloud cover reaches at-40℃to-55℃when the severe convection is occurring in northwest Shandong, while the most intense hail and gale weather mainly occur in which there is the largest brightness temperature gradient region in front of thunderstorm cloud. The analysis of CINRAD Doppler radar data shows that the severe convection in the northwestern Shandong is mainly causing by the super-cell and multi-cell storm on the "bow" echo whose center intensity are above 55dbz, the maximum reaching 65dbz. The super cell storm at the top of bow echo causes the most severe weather, with mesocyclone existence in the lower-level and the radial velocity positively correlated with the surface wind speed; VIL is above 50 kgm-2 in the zone where hail occurs, indicating that VIL products is very good correlated with hail, while its value can be a good indication to the existence of hail.更多还原