Study on Formation Mechanisms of Heavy Rainfall Within the Meiyu Along the Mid-Lower Yangtze River and Theories and Methods of Their Detection and Prediction          下载免费PDF全文

NI Yunqi  ZHOU Xiuji 《Acta Meteorologica Sinica》2006,20(2):191-208

As the project of National Key Basic Research Development Program: Research on Formation Mechanisms and Predictive Theories of Major Weather Disasters in China has been fulfilled by 5-yr efforts of Chinese scientists, achieving results of great significance are as follows: 1) development of multi-scale physical models for Meiyu frontal heavy rainfall based on a range of real-time observations; 2) construction of synoptic models for such heavy rainfall; 3) the Meiyu front found to consist of multi-scale systems that represent a subtropical front, which shears structural features of an extratropical front and ITCZ, displaying sometimes a bi-front feature in the mid-lower Yangtze Basin (MLYB). The positive feedback between pre-frontal wet physical processes and over-front strong convective activities as well as interactions among multi-scale systems of the Meiyu front act as the important mechanism for the maintenance and development of the Meiyu front; 4) proposal of theories and methods for quantitative retrieval of multiple mesoscale torrential rains from satellite remote sensings, leading to a line of products; 5) investigation of applicable theories and techniques for retrieving the heavy rainfall system's 3D structure from dual-Doppler synchronous detectings; and 6) development of a system for meso heavy rainfall numerical prediction models with a 3D variational data assimilation scheme included, a tool that played an active role in flood combating and relief activities over the Huaihe River Basin (HRB) in 2003.  相似文献   

GRAPES模式中的坡地辐射方案及其对短期天气过程模拟的影响   总被引：6，自引：4，他引：6  

沈元芳  胡江林 《大气科学》2006,30(6):1129-1137

为了改进太阳短波辐射参数化, 在非静力中尺度模式GRAPES (全球/区域同化和预报系统) 中考虑了坡地辐射 (SLOPE), 并着重讨论其在不同分辨率情况下对我国短期天气过程的影响.数值试验结果表明: 地形坡度和坡向对地表短波辐射 (GSW) 计算有较大的影响, 与没有考虑坡地作用的参考运行 (FLAT) 相比, 早晨和傍晚的GSW最小可减小60%以下, 最大也可增加60%以上, 比一天中其他时间和平均值大得多.在江淮流域一次梅雨锋降水过程中, 坡地辐射参数化方案的引入对降水模拟有较明显的影响, 特别在高分辨率 (6 km) 情况下, 降水的增加和减小不仅发生在GSW改变比较大的地区, 且与复杂地形有较好的相关性.另外, 由于地形坡度和坡向引起地表温度的改变与地表热通量的变化一致, 且也发生在地形起伏的多山地区.因此, 当水平分辨率较高且地形陡峭起伏时, 应当包含坡地辐射.  相似文献   

云南冷锋切变型暴雨的中尺度特征分析   总被引：8，自引：0，他引：8  

张秀年  段旭 《南京气象学院学报》2006,29(1):114-121

利用T106数值预报产品资料，通过中尺度滤波方法，提取云南冷锋切变型暴雨过程中的中尺度降水系统，对其有关物理量的特征及演变进行了分析。研究发现，通过中尺度滤波方法，可以从常规的数值预报产品资料中有效分离出直接导致暴雨的中尺度天气系统，通过对这些中尺度系统的分析及追踪，可以为暴雨预报提供更为客观的预报依据；水汽的强辐合时段与暴雨降落时段有较好的对应关系，暴雨落区比水汽的强辐合区域要稍偏向于水汽输送的下游方向；在该型暴雨的发生过程中，北部冷平流具有十分重要的作用，但南部暖平流的作用也不可忽视。  相似文献   

近44年无锡寒潮天气变化特征分析   总被引：2，自引：0，他引：2  

阮蔚琳  马志强  章志芹 《湖北气象》2007,26(2):139-143

利用无锡市1959～2002年共44a的逐日最低气温资料,分析了无锡寒潮发生的特点.分析结果表明:无锡寒潮的年发生次数有线性减少趋势;寒潮减少主要发生在10月、12月、4月.分年代看,从20世纪60年代到80年代逐年代减少,但90年代又增多.寒潮减少与降温幅度减小、最低气温升高有关,其中最低气温升高是其主要影响因素.特征区域的500 hPa高度场偏高是寒潮发生次数减少的直接原因.最后,针对多寒潮年和少寒潮年的环流特点,给出了500 hPa典型距平场特征.  相似文献   

"99.6"梅雨锋暴雨模拟资料的诊断分析     

王文  蔡晓军  隆霄 《干旱气象》2007,25(4):5-11

利用非静力中尺度模式MM5V3的模拟资料对"99.6"梅雨锋暴雨过程进行了对流动量输送(CMT)和视热源视水汽汇分析。CMT诊断分析表明,水平动量残差在切变低涡发展的不同阶段的作用是不同的,在中尺度低涡发生初期对流层低层动量残差X主要是加速西南气流的北上;在对流层中层动量残差在槽后加速冷空气南下,在槽前加速西南暖湿气流北上,非常有利于东亚大槽的发展。在低涡切变线强烈发展时,850hPa的X方向与发生阶段相反,此时西南气流受到了强烈的减速作用,同时500hPa东亚大槽的前部和后部出现了减速气流的动量残差,槽后冷空气和槽前的暖湿气流都已经受到减速作用,此后低涡切变线逐渐衰减。低涡切变线发展到最强的阶段,强X矢量几乎总是与强烈上升运动区相对应,能量转换E的水平分布表明,大尺度系统与中尺度系统之间的能量转换非常复杂,并不是简单的能量串级过程,但能量主要是从大尺度向次网格尺度转换。200hPa动能转换E的带状分布非常清楚,E的正负大值中心分布在高空急流的2侧,表明高空急流在能量转换的过程中起到非常重要的作用。视热源和视水汽汇的诊断分析显示,强凝结潜热的释放与低涡的发展相伴随,但视热源只与β中尺度系统有明显的对应关系,视水汽汇有和视热源非常相似的分布特征。  相似文献   

西太平洋副热带高压影响下北京区域性暴雨的个例分析   总被引：9，自引：3，他引：9  

刘还珠  王维国  邵明轩  王秀荣 《大气科学》2007,31(4)

北京地区大降水(≥25 mm/d)天气有72%出现在7~8月份,其中直接受西太平洋副热带高压(副高)影响的大降水占46%,它们主要产生在西风槽与副高相互作用的天气形势下。通过对该类暴雨的典型个例分析表明,由于受副高的影响,对流层低层副高南面的偏东气流将海上充沛的水汽输送到大陆,并折向北与偏北气流相遇,汇集在北京附近。同时,副高西北边缘与西风槽之间形成较强的能量锋区,该锋区南面的高温高湿气团蕴藏了较深厚的湿有效位能,在湿位涡的斜压项作用下转化为动能,倾斜垂直涡度发展激发了强烈的上升运动。在斜压扰动作用下,对流层中层差动涡度平流和副高西侧的暖平流破坏了北京及邻近区域的准地转平衡,动力强迫和热力强迫共同作用激发了次级环流,该处的上升运动得到加强。暴雨就是产生在强的能量锋附近低层气旋性涡度发展、高层辐散显著的地方。此外,副高西侧低层的暖湿气流北上,较强的差动假相当位温平流促使大气层结向对流不稳定发展,这对于暴雨局地的再增强是不可忽视的因素。由此,形成对该类暴雨天气预报的着眼点。  相似文献   

Diagnostic analyses of convective events — The effect of propagating gust fronts     

Marek Ka&#x;par  Miloslav Müller 《Atmospheric Research》2007,83(2-4):140-151

This paper is devoted to the testing experiment of a postprocessing tool aimed at the objective analysis of propagating gust fronts in a given convective environment. The tool is being developed to be applicable in the operational mode by utilizing NWP model outputs. The experiment was carried out on two summer convective cases which occurred in the Czech Republic. The cases were numerically simulated by the limited area NWP model LM COSMO with the horizontal resolution of 2.8 km. They represent different types of convective systems, both accompanied by objectively identifiable gust fronts and causing heavy precipitation. The event from July 2000 was characterised by the development of isolated thunderstorms. The other event from July 1998 was a long-lasting and organised convective system — a squall line. The hypothesis was that the developed postprocessing tool is capable to evaluate the role which downdraft outflows played in the decay and initiation of convective cells by interaction with convective environment and thus in prolongation of convection lifetime.The procedures of the Objective Analysis of Gust Fronts (OAGF) were applied to the thermodynamic outputs of the LM COSMO. The aim was to determine the position of gust fronts within the domain and to assess their speed of movement and the potential to initiate convection according to the properties of ambient vertical shear and stability as well as humidity conditions ahead of the respective downdraft outflows. In addition, the Radar Simulation Model (RSM) was employed to monitor the simulated convective systems in arbitrary PPI and RHI scans and to verify qualitatively the LM COSMO precipitation forecasts.The case studies has confirmed the applicability of the LM COSMO–OAGF chain and RSM, which may represent the potential for improving the operational nowcasting of hazardous convection phenomena. In both simulations, the objective gust fronts moved on into the vertical shear-favourable environment for triggering new convection. In addition to the dynamical organisation, there were also favourable stability and humidity conditions in the area of forced upward motions in the simulation of the event from July 2000.  相似文献   

Methane-induced dolomite “chimneys” on the Kuroshima Knoll, Ryukyu islands, Japan     

Rika Takeuchi  Ryo Matsumoto  Shigenori Ogihara  Hideaki Machiyama 《Journal of Geochemical Exploration》2007,95(1-3):16

The Kuroshima Knoll is about 26 km south of Ishigaki Island in the southern part of the Ryukyu Arc. The area is considered to be the source area of “The 1771 Yaeyama Earthquake Tsunami”, which was due to the submarine landslide caused by an earthquake. It has been cleared from some investigations using “Dolphin 3K” and “Shinkai 2000” that there are large-scale dead Calyptogena colonies, many gravels of fallen dolomite chimneys and carbonates on the top of the Knoll [Matsumoto, T., Uechi, C., Kimura, M., 1997; Machiyama, H., Matsumoto, T., Matsumoto, R., Hattori, M., Okano, M., Iwase, R., Tomaru, H., 2001b.]. Carbonates of Kuroshima Knoll have various shapes and macroscopic textures. These have been classified into 4 types; shell crust (pavement), chimney, burrow, and nodule. It is clear that all chimney and burrow carbonates are composed of dolomite, while shell curst and nodule are composed of calcite, sometimes both calcite and dolomite. These carbonates are considered to have been formed by cold seep, because they are characterized by the light carbon isotopic ratio (semi-biogenic) and the heavy oxygen isotopic ratio. This suggests that methane hydrate layers develop under this survey area and the water that has the heavy oxygen and the light carbon isotopic ratio is derived from the dissociation of methane hydrate.  相似文献   

长武地区三角洲前缘短期基准面旋回与储层成因特征     

陈金荣 《沉积与特提斯地质》2007,27(4):45-49

长武地区延长组78、油组三角洲前缘储集砂体,按成因可分为三大类5种类型,各种类型砂体的成因明显受基准面升降、可容纳空间和沉积物补给量之间变化关系的影响。在基准面上升过程中,可容纳空间/沉积物补给量的比值对砂体成因特征的控制作用主要表现为:小于l时,以截削式河道砂体为主;大于1时,则为完整式河道砂岩。在基准面下降过程中,可容纳空间/沉积物补给量小于l时,以孤立式河口坝砂体为主;大于1时,则以远砂坝砂体为主;在水下坡折带沉积区,则为复合式坝砂体。基准面升降过程中,短期基准面旋回的规律性变化,影响着不同成因的砂体类型的分布特点。  相似文献   

梅雨锋的典型结构、多样性和多尺度特征   总被引：3，自引：1，他引：3  

郑永光  陈炯  葛国庆  朱佩君 《气象学报》2007,65(5):760-772

在天气尺度梅雨锋的天气学定义基础上,利用GMS-5静止卫星红外云图、常规气象探空资料、NCEP再分析与最终分析资料对2002年长江流域典型梅雨期6月26—28日和二度梅期间7月23日、1998年5月梅雨与7月二度梅共4个梅雨锋个例进行了分析与比较,归纳了梅雨锋结构多样性;并着重对典型梅雨期的梅雨锋发展过程、水平以及垂直结构进行了多种物理量场(包括风场、温度场、急流、锋区、假相当位温、散度、垂直速度、静力稳定度等)的综合分析。结果表明,不同的个例,不同的地区和时期,一次梅雨过程的不同阶段,梅雨锋的结构和性质都有可能不同,它可以从比较接近极锋的性质过渡到接近赤道锋的性质。在水平结构上梅雨锋是在高、低纬度不同尺度的环流系统共同作用下形成的,从而造成了梅雨锋结构具有丰富的多样性。对典型梅雨锋结构进行综合分析表明梅雨锋对流层中下层锋面由强假相当位温水平梯度形成;梅雨锋南侧为暖湿气团、北侧为变性气团;梅雨锋南面为西南季风、北面为偏东气流;梅雨锋的上升运动和强降水主要发生在梅雨锋的前沿;梅雨锋上方对流层上半部存在与副热带高空急流相配合的高空副热带锋;对流层上部的高空热带东风与副热带高空西风急流构成了梅雨锋降水的高空辐散流场。根据典型期梅雨锋以及二度梅倾斜型梅雨锋的对流层上、中、下水平环流特征,给出了梅雨锋的多尺度概念模型,主要包括中低纬度系统相互作用、对流层高层的行星尺度的环流系统副热带高空西风急流、高空热带东风急流与南亚高压、对流层中层的副热带高压与北方的短波槽以及对流层低层的行星尺度季风和切变线。  相似文献