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暴雨天气动力过程及强降水增幅机理的研究 【作者】濮梅娟 【导师】陆维松

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-D*j*PSFG0w|0暴雨天气动力过程及强降水增幅机理研究

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【作者】濮梅娟导师】陆维松
p u h MYq]e0【作者基本信息】南京信息工程大学,气象学,2005年,博士水利论文.T+O#z-F:Hhy

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【中文摘要】 暴雨是影响江苏的主要灾害性天气之一。1954年、1991年、1998年、2003年江淮流域的洪涝,2000年8月底,江苏东北部的洪涝等,都是由暴雨或大暴雨引发。本文运用天气学、统计学、动力诊断和数值模拟方法,对影响江苏的梅汛期暴雨和台风暴雨过程进行了分析,对暴雨的环流特征、中小尺度天气系统、动力热力条件和强降水的增幅机理等进行了比较细致的探讨,获得了一些有意义的结果。 1.分析了暴雨天气环流特征和动力热力条件。对江苏2003年梅汛期暴雨和非暴雨过程进行合成分析,得出江苏梅汛期暴雨天气过程环流特征和热力动力条件:500hPa上中纬度有华北低槽,西太平洋副高季节性北抬西伸,120°E脊线在26°N,586线在长江口,四川西部浅槽东移,冷暖空气交汇于淮河流域以南地区。有暴雨日,地面均有冷锋或静止锋与之配合,锋面的位置偏北(在31—34°N之间)。副高西侧有西南或偏南低空急流(≥12m/s)向江苏输送暖湿气流,使垂直方向的温湿层结结构发生变化,构成对流不稳定,上下层温湿差动平流,使不稳定能量由低值区向高值区积累。急流附近非地转风使气压梯度力与地转偏向力不平衡,风场低层垂直切变增大,里查逊数(R...更多i)随之减小。涡度、散度、垂直速度合成垂直剖面图上:低层辐合,高层辐散,无辐散层在400hPa附近,暴雨发生在较深厚层次的上升运动中,沿119°E垂直速度经向剖面图上,江苏淮河流域(32—33°N),垂直速度ω<0,从地面一直伸展到500hPa以上,最小负值为-25×10-3hPa/s。非暴雨过程则反之,基本为下沉区,ω≥0。 2.揭示了中尺度对流复合体MCC活动特征和发生发展条件。运用卫星红外云顶亮温(TBB)资料,分析了2003年7月4—5日大暴雨天气过程中尺度MCC活动特征表明,影响江苏的中尺度MCC由典型的中—β(γ)云团组成,大暴雨区与TBB<-70℃区域对应,降水强度与TBB成正相关,即TBB值越低,降水越强。在成熟期中,TBB最低值达到-75℃以下,对流通常都突破了对流层顶。较强的高空辐散、低层辐合对梅雨锋区产生中尺度低值系统有激发作用,有利的环境场形成的高空辐散、低空辐合和上升运动是中尺度MCC发生发展的重要条件。气旋性涡度场对积云对流活动具有组织和增强作用,中尺度MCC的发展与涡度经向剖面图上深厚的中尺度涡管相对应,涡管向垂直方向发展,MCC强烈渡梅娟博士论文摘要发展。对流不稳定对MCC发生具有触发作用,低层暖湿不稳定气流的维持,水汽、能量的聚集,是MCC发展的基础,MCC发展是江苏暴雨的直接制造者。 3.揭示了暴雨的多普勒天气雷达回波特征。分析多普勒天气雷达径向速度、回波强度、反射率、风暴相对速度、垂直风廓线等产品,发现在多普勒径向速度图上,暖平流与大尺度辐合在测站近距离迭加和在较远距离存在冷平流,有利于水汽垂直输送和辐合上升运动,有利于暴雨的产生。逆风区存在垂直风切变,辐合气流很强,是分析产生暴雨的一个重要指标。强回波中心朝着辐合区方向移动。降水回波中,积云和积雨云强度超过45dBz的强回波具有极高的降水效率。强降水时段,垂直风廓线图上风向随高度强烈顺转和风向随高度逆转,均能产生短时的强降水。如果从底层到中高层均转为偏北风,强降水将迅速结束。这些与暴雨中小尺度系统发生发展相关的特征,为进一步开展暴雨分析和预报提供了参考。 4.揭示了暴雨中尺度系统发生发展及强降水增幅的物理机理。通过2000年8月30一31日江苏省东北部特大暴雨过程分析,发现中尺度系统是特大暴雨产生和增幅的重要成员。中一p尺度的能量锋区,是特大暴雨维持和增幅的主要中尺度系统。利用锋生函数对地面中一p尺度能量锋区的发生发展进行诊断表明:锋生函数的变形项起了决定性作用,辐合项也有较明显的贡献,非绝热加热项作为一种可能的触发机制,在锋生初期有着重要作用,但对锋区的维持,其贡献并不明显。利用二维中尺度方程对锋区进行数值模拟表明:在能量锋区附近驱动产生了垂直涡旋,在涡旋上升支部位,将高能区的暖湿空气向上输送形成降水,使原有降水强度增强,在涡旋下沉支通过下沉气流使雨滴迅速下落,同时拖曳冷空气使地面降温,使得锋区维持和加强,致使涡旋得以维持或增强,再次促使雨强增幅。 中一p尺度能量锋区形成以后,在锋区附近产生中一p尺度东风辐合线系统,响水之IOmm雨团的高频区(共21个频次)与中一p尺度东风辐合线高频次的准东西向和准南北向分布,更替相关,其辐合线高频区和雨团的主频区相一致。 分析地面速度平流散度F得出,强雨团与F>0的强中心趋于一致,当aF_,一一~,、.一一一,.一.一、,,,、__刁尸_.‘._牛>O时与强雨团的维持及其雨强增幅关系十分明显,即兰兰>0时,辐合增强,次--------一’一”-一’----一’次  还原

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【英文摘要】 Rainstorm is one of the main disastrous weathers that affect Jiangsu. Regional floods happened in 1954, 1991, 1998 and 2003, and local flood happened in the northeast of Jiangsu at the end of August 2000, etc., were all resulted from rainstorms or heavy rainstorms. By means of synoptic meteorology, statistics, dynamical diagnosis and numerical simulation, this paper analyzed the rainstorm courses affected Jiangsu, which occurred during Meiyu flood season or resulted from typhoons, and discussed the circulation character, meso-micro synoptic systems, dynamic and thermal terms, and intensification mechanism of rainstorm, etc., thus acquired some meaningful results.1. Analyzed synoptic circulation character, dynamic and thermal terms of rainstorm.According to the synthesizing analysis of the rain courses happened in Jiangsu in Meiyu flood season of 2003, came to the conclusion of circulation character, dynamic and thermal terms of rainstorm courses as follow. North China trough exists in ...更多middle latitude, the subtropical high of west Pacific origin seasonally lifts to the north and stretches to the west, at 120°E, and its ridge line reaches 26°N, 588 isopotential reaches the estuary of Yangtze Rivers, there is a shallow trough move towards east from the west of Szechwan, the cold and warm air interjunction locates in the south region of Huaihe valley. On rainstorm days, there always are cold fronts or stationary fronts in the surface charts cooperate with the upper systems, and their position is partial to the north(between 31-34°N). On the west side of the subtropical high, a low level jet stream(in southwest or partial to south direction, ≥12m/s) transports warm moisture towards Jiangsu, making change to the vertical structure of temperature and moisture, thus constitutes convection unsteady and forms differential advection of temperature and moisture between upper and low levels, resulting in unsteady energy accumulation. Near the jet stream, ageostrophic wind makes imbalance between pressure gradient force and geostrophic deflecting force, vertical shear increases in the low level wind field, Richardson number(Ri) minishes accordingly. In the vertical cross section of vorticity, divergence and vertical velocity, convergence exists in low layers, divergence exists in upper layers, and nondivergence exists near 400hPa geopotential height. Rainstorm occurs in the deep ascending motion region, in the vertical cross section of vertical velocity along 119°E, it shows that w<0 in Huaihe valley of Jiangsu(32-33°N), from the surface to 500hPa geopotential height, and the minimum is -25 X 10-3hPa/s. Whereas, in the non-rainstorm courses, descending motion occurs in thesame region , and2. Disclosed the activity character of compound meso-scale convective cells (MCC), and terms of its occurrence and development.On the basis of the data of brightness temperature of infrared cloud top, analyzed the activity character of MCC that resulted in heavy rainstormm course occurred from July 4 to July 5,2003, disclosed the following fact: the MCC affected Jiangsu was comprised of typical meso- β ( γ ) cloud masses, heavy rainstorm area was corresponding to that of TBb<70℃, lower TBb resulted in stronger precipitation intensity. During MCC maturing stage, the lowest value of TBb could get under -75℃ and the convection usually broke through the tropopause. The strong upper level divergence and low level convergence can cause meso scale low system in Meiyu frontal zone, the foregoing two factors plus ascending motion in furthersome circumstance are the important terms of the occurrence and development of MCC. Cyclonic vorticity field can organize and strengthen the convection of cumulus, the development of MCC is corresponding to the deep meso scale vortex tube in the latitudinal vertical cross section of vorticity, the vortex tube developes vertically thus MCC developes strongly. The convective instability triggers the occurrence of MCC. The maintenance of warm and moist instable airflow, the accumulation of vapor and energy a  还原水利论文,M fl0| hgZ/lCM

2m ROcZ.E-wQ!@0N)]0【中文关键词】 暴雨; 动力过程; 雷达探测; 数值模拟水利论文%K.k0A;\7^!WW
【英文关键词】 rainstorm; dynamic process; radar detecting; numerical simulation
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