【作者】 戴廷仁；

【导师】 寿绍文；

【作者基本信息】 南京气象学院 ， 气象学， 2003， 硕士

【摘要】 应用MM5模式对受华北气旋影响所产生的2003年8月5～6日东北地区暴雨天气进行了数值模拟，较成功地模拟出了这次过程。大范围偏南气流及其中的中尺度急流带来的水汽输送及辐合，为暴雨天气的发生、发展提供了低层水汽条件。中层干冷空气下沉及低层暖湿气流爬升是强对流不稳定能量积累的重要机制。能量锋区为产生强对流提供了能量条件。低层低空急流脉动产生的强辐合，高空急流诱发的高层强辐散是本次东北地区暴雨天气的直接触发机制。对流层中低层比较大的垂直速度为强对流的触发提供了动力条件。通过对等熵面的位涡分析，发现了对流层中低层的位涡场，在气旋上方有一个相对高位涡中心，由此使得气旋在一个比较深厚的气旋性环流中发展；而对流层高层则是一个伴有较强位涡低值的反气旋环流区。低层的气旋性环流和高层的反气旋性环流相配合，有利于形成低层辐合，高层辐散，使得气旋附近的上升气流得以维持和加强，从而为对流性降水提供了必要条件。通过对等压面的位涡分析，发现了在暴雨发生前，在对流层低层有正位涡扰动存在并向北形成倾斜的扰动柱，同时也反映了对流层低层正位涡扰动对强对流天气的触发作用；随后高层正位涡向下扰动，形成一个垂直扰动柱，这时对应降水的发展阶段：在暴雨的鼎盛阶段，600～700hpa上空维持水平分布的等值线，在其上还有正的位涡扰动；当近地面出现负的位涡扰动时，降水随之也减弱。分析表明Q矢量散度场多呈条块状的辐合、辐散区相间分布的形式，反映了中尺度特性。在对流层低层Q矢量散度辐合区和辐散区的交界处，伴随有较大的对流性降水，对流性降水的强度随辐合中心强度的增强而增强，随辐合中心强度的减弱而减弱。通过分析我们发现了正的相对螺旋度中心与850hpa低空急流的演变过程是一致的。在正的相对螺旋度中心的左侧，3小时后出现3h积云降水量的高值中心，也就是说正的相对螺旋度中心和3h积云降水中心不同步，3h积云降水中心落后于相对螺旋度中心。相对螺旋度值的变化大致反映了暴雨及其系统的强弱趋势。更多还原

【Abstract】 A rainstorm in northeast China affected by the North China cyclone during 5~ 6 August 2003, was successfully simulated by MM5 model in dais paper. Big scope south airflow and vapor transport and convergence brought by meso-scale jet, offer vapor condition which rainstorm occur and develop. Energy front has offered energy condition to produce severe convection. Severe convergence brought by Low-level jet pulsation, and severe divergence brought by upper-level jet is directly trigger mechanism of this intense rainstorm. The severe vertical velocity is severe convection trigger to offer dynamical condition for severe convection generation in lower-troposphere.Through analysis of potential vorticity in equity-entropy surface field, a relatively high potential vorticity center in cyclone top in low-troposphere have discovered, and make cyclone develop in a more deep cyclone circulation by this; And an anticyclone circulation zone with more severe low potential vorticity in high-troposphere. Low-level cyclone circulation with high-level anticyclone circulation, is helpful to form low-level convergence and high-level divergence, and make the rising airflow nearby cyclone keep and strengthen so that have offered necessity condition for convection precipitation. Through analysis of potential vorticity in isobaric surface field, in low-troposphere a positive potential vorticity disturbance exist and form incline disturbance column northward before rainstorm generation, at the same time have also reflected positive potential vorticity disturbance for severe convection weather trigger role in lower-troposphere; Soon positive potential vorticity disturbance in high-troposphere downward, form one vertical disturbance column, now corresponding precipitation develop stage; In the prosperous stage of rainstorm that maintains isolines of horizontal distribution and still have straight positive potential vorticity disturbance in 600 -700 hpa isobaric surface field; When near ground arises negative potential vorticity disturbance, precipitation also weaken.Q vector divergence field submit piece form district of convergence and divergence,have reflected meso-scale character. In the interface of convergence district and divergence district of Q vector divergence, accompany severe convection precipitation and convection precipitation strengthen following convergence center strength, weaken following divergence center weaken.The positive storm-relative helicity center is accompany with low-level jet in 850-hpa isobaric surface fields. Severe cumulus precipitation of 3h center appear in the left side of positive stonn-relative helicity center, i.e. positive storm-relative helicity center is not synchronization with cumulus precipitation center of 3h, the cumulus precipitation center of 3h falls behind the positive storm-relative helicity center. The change of the positive stonn-relative helicity value has reflected the severe weak tendency of rainstorm and its system approximately.更多还原