【作者】 刘蕾；

【导师】 丁治英；

【作者基本信息】 南京信息工程大学 ， 气象学， 2011， 硕士

【摘要】 华南地形复杂多变,局地强对流天气频繁发生又难以预报。要准确模拟华南地区的降水情况必须考虑地形的影响。本文利用NCEP/NCAR全球客观分析资料,云顶亮温TBB资料以及中尺度模式WRFV3.1.1,对发生在2008年6月5日～7日的华南暖区暴雨过程进行了数值模拟及诊断研究。分析发现,850hPa低层低涡的形成和维持、200hPa高空急流右后方的辐散场,500hPa副热带高压西北侧的西南气流以及高原槽的东移为本次特大暴雨产生提供了天气尺度、次天气尺度的背景场。此外,来自南海的水汽为暴雨的发生提供了充足的水汽条件。由于本次暴雨过程发生在云雾山的东南侧,为了了解地形对本次暴雨的影响,设计了一个考虑地形重力波拖曳(GWDO)参数化方案的敏感性试验和未考虑此方案的控制试验对该次暴雨过程进行模拟,通过与实况对比分析后,得出：模式中考虑了GWDO参数化方案的敏感性试验较好地模拟出了广东阳江地区强降水的中心和强度,再现了暴雨过程中大尺度环流形势及其演变状况,成功地复制了中尺度低涡的位置及移向,而未考虑此方案的控制试验没能模拟出此次暴雨,其在中心位置和降水强度方面都与实况差别较大；GWDO参数化方案的引入有效地减少了由地形引起的对流层中层纬向风的偏差,比较合理地模拟出了地形对气流的影响；分析得出地形引起的重力波为本次暴雨提供了中尺度的触发机制,地形重力波的拖曳作用是导致暴雨在阳江附近停滞少动的主要原因。由地形敏感性试验得出,云雾山地形在降低和按比例缩小后,降水强度都较控制试验大大较弱,降水的中心位置都出现了北移；地形按比例升高后,雨带呈椭圆形分布,降水中心为270mm,但还是较控制试验弱,降水落区与实况较为接近。另外云雾山地形的改变对强降水期间中-γ背风坡低涡的生成与位置有重要影响。利用WRF模式输出的高分辨率数据,采用HYSPLITv4.9气流三维轨迹模式追踪暴雨中心高低层气流运动轨迹,发现此次暴雨过程中没有偏北冷空气的影响,暖湿气流主要来自于南海。高层辐散先于低层辐合出现,南亚高压的高层辐散可能是本次暴雨过程的一个诱发原因。从对流涡度矢量垂直分量的发展演变和地面降水的关系来看,对流涡度矢量垂直分量在时间和空间上与地面降水分布具有较好的对应关系,对流涡度矢量垂直分量对示踪暴雨系统的发生发展有一定的指示作用。更多还原

【Abstract】 The contribution of sophisticated terrain is a key factor of the generation of strong convective weather which is difficult to forecast. In order to improve rainfall simulation of South China in the model, the impact of terrain must be taken into account. In this paper, the rainstorm in warm section occurred in South China during the period from 5-7 June 2008 is investigated by using NCEP/NCAR objective analysis data with resolution of 1°×1°four times a day, the temperature of brightness blackbody on cloud-top(TBB) data for l-hour,and the mesoscale model WRFV3.1.1.It is found that the formation of low-vortex at 850hPa, the divergence in the behind of the jet stream at 200hPa, the southwest airflow from the northwest of subtropical high and the short-wave trough which towards the east provide the large-scale and sub-weather-scale circulation background field of the rainstorm. In addition, the water vapor from the South China Sea provides a good condition for this rainstorm.In this article, in order to realize the influence of this terrain, the rainstorm in warm section occurred in the southeast of Yun Wushan will be investigated for two experiments by one using Gravity Wave Drag by Orography (GWDO) Parameterization which is additional in WRFV3.1. They have been simulated by using the analysis of NCEP (1°×1°) from 5 to 6 June 2008. With an analysis of the comparison of the two experiments, the results are as follows:Sensitivity experiment achieved a success in the simulation of the center and strength of the rainstorm. It succeeds to reappear the large-scale circulation and the evolution of state formed during heavy rain, and successfully duplicates the mesoscale low-voxtes whose temporal evolution characteristics are in accord with the movement of the precipitation center, while the control experiment failed. The using of GWDO Parameterization effectively reduces the zonal wind deviation in the middle troposphere and reasonably simulates the dynamic uplift of airflow caused by terrain. According to experiments, the energy divergence in the middle caused by orography-induced gravity wave is the main cause of rainstorm, which enhances the vertical movement and makes the precipitation strengthen and relatively concentrated.The results of topography experiments show that, the precipitation intensity and its position has much to do with terrain. The intensity of precipitation is much weaker than control experiment, and the rainfall center position appeared more northward whatever the terrain of Yun Wushan is flat or it is reduced in proportion. The rain belt appears Oval-shaped distribution after the terrain increased in proportion, while its precipitation at center is 270mm which is smaller than control experiment, and its area is close to real state. Furthermore, the change of terrain has evident impact on the generation and position of theγmesoscale lee vortex during the period of heavy rain.This paper uses HYSPLITv4.9 three-dimensional air flow trajectory model to track the trajectory of the upper and lower flow at the center of the rainstorm, by employing more reliable high-resolution data sets obtained by WRF model. The results show that the cold air has little or no effect on the rainstorm, and the warm flow is mainly from the South Sea. Upper-level divergence occurs before the low-level convergence, and the upper-level divergence of South Asian High may be one of the induced causes of the heavy rainfall. From the relationship between the vertical component of convective vorticity vector (CW) and rainfall, the vertical component of convective vorticity vector (CW) is highly correlated with rainfall in time and space, and it is a good indicator for tracing the development of rainstorm system.更多还原