【作者】 袁媛；

【导师】 沈桐立； 沈新勇；

【作者基本信息】 南京信息工程大学 ， 气象学， 2008， 硕士

【摘要】 我国陕北地区下垫面性质复杂,多数地方年降雨量少,每年暴雨日数也很少:陕北由于特殊的地理环境和常年少雨的状态,使得该地区各种设施和自然物的防雨能力较差,一旦发生暴雨往往会造成山洪爆发、泥石流等灾害,所以对这一地区暴雨的研究显得十分重要。本文首先利用FY-2C卫星T_bb资料、常规资料以及NCEP1°×1°的6h再分析资料对2006年9月20日20时-21日11时陕西北部的一次暴雨过程进行诊断分析,结果表明:700 hPa存在一支较强的偏南气流,该气流北伸的位置与暴雨的落区有关;暴雨前期,850 hPaθ_se场呈典型的“Ω”型;850 hPa和700 hPa的西南气流为暴雨提供了充足的水汽;强烈的上升运动将触发不稳定能量释放,有利于强降水天气的发生发展:暴雨发生时,暴雨区基本位于或接近于螺旋度的大值区。T_bb的最低值与暴雨中心对应较好。应用WRF中尺度模式对陕北“06.9”暴雨过程进行数值模拟,应用模式输出的基本物理量分析了涡度、散度、垂直速度和相对湿度并计算了干位涡、湿位涡正压、斜压项以及扰动位涡,揭示了这次暴雨产生的机理。诊断分析发现:湿度场和垂直上升运动的相互耦合是本次暴雨发生发展和维持的动力机制。暴雨中心位于700 hPa干位涡的大值中心附近;MPV1高值与对流稳定的冷空气相联系,较小的MPV1正值或负值区域和对流不稳定或对流稳定程度低的暖湿空气相联系,低层MPV1的负值区能表征不稳定的暖湿气流活动特征,暴雨发生在零线附近;偏南暖湿气流被源源不断输送至与MPV2负值区相联系的辐合区中,由于辐合所造成的强烈的垂直运动,使暴雨的强度急剧增大,形成这次陕北地区的大暴雨过程。中低层正值位涡扰动的存在是暴雨发生发展的重要条件。利用模式输出结果进行了Q矢量的分析,揭露了暴雨期间准地转Q矢量散度场、Q矢量场与暴雨之间的时空配置关系,指出了Q矢量在暴雨预报中的作用。做了地形敏感性试验,试验结果可以看出,秦岭山脉对陕西北部降水有一定的影响。尝试利用从风云2号气象卫星上获得的图像数据计算而来的云迹风资料,对中尺度数值预报模式的初始场进行改善,初步探讨云迹风资料在陕北暴雨研究中的应用,对陕北暴雨的精细化预报有所改善。更多还原

【Abstract】 The topography of northern Shaanxi province area is very complicate.Most places have the small precipitation rain fall and few rainstorms.Because of particular geography circumstance and small rain fall in the northern of Shaanxi province,the establishments that are used to prevent the rain there is not good enough.The disaster,such as flood and sparry flow,are often caused by rainstorm.So it is very important to research the rainstorm of this area.In this paper,first of all,the t_bbdata of FY-2C satellite,routine data and the 6 hour NCEPl°×1°re-analyzed data are used to perform a diagnoses about a rainstorm of northern Shaanxi province at the night of 20^th.September,2006.The result shows that there exists a stronger southern airflow in 700 hPa whose position is associated with the rainstorm area.The low value of T_bbis corresponding to the center of rainstorm.The field of 850 hPaθ_seis presented as the type of"Ω".The airflow of 850 hPa and 700 hPa provides the rainstorm enough vapor.The release of unstable energy is caused by strong rising movement that is good at presenting the strong precipitation.When the rain occurred,the area of the rain is located in or approached the high area of helicity.A heavy rainstorm of 20^th.September,2006 is numerical simulated by meso-scale mode of WRF.Vorticity,divergence,vertical speed and relative humidity is analyzed with the basic physical element of mode output.Potential vorticity,humidity potential vorticity barotropic, baroclinic item and disturbance potential voriticity are calculated,It finds out the mechanism of the rainstorm.The diagnostic analysis shows that the coupling of humidity field and vertical rising movement is the dynamical mechanism that makes the rainstorm occur and last.The center of the rainstorm is located around the major area of 700hPa potential vorticity.The high of MPV1 is isolated with the convective stable cold air.The smaller positive or negative value area is isolated with the unstable or less convective stable warm air.The negative area of the lower MPV1 can signifies the character of the unstable warm air movement.The rainstorm happened around the zero line.The south warm air is transferred continuously to convergence area.This area is isolated with the MPV2 negative area.Because of the strong vertical movement caused by convergence,the intensity of the rain is raised,The heavy rainstorm is formed.The existence of middle-low positive potential voriticity disturbance is the important condition of the rainstorm development.The vector Q is analyzed by using mode output.The result posts the relationship of space-time configuration among the divergence of qusi-geostrophic vector Q,vector Q and rainstorm.It points out the effect of vector Q in the rainstorm forecast.The sensitive experiment shows that Qinlin mountains affect the rain fall of northern Shaanxi province.The initialization field of meso-scale numerical mode is improved by using the the cloud drift wind data calculated by the image data from the fenyun satellite.The using of cloud drift wind in the northern of Shaanxi rainstorm forecast experiment is elementarily discussed.It is useful for the fine forecast of northern Shaanxi province rainstorm.更多还原