摘要
利用非静力平衡模式(MM5 V3.5)对2001年8月23日发生在华北地区的一次强对流风暴过程进行了数值模拟,在取得合理模拟结果的基础上,着重分析了风暴发生的热力条件、太行山地形动力作用和风暴中尺度结构特征,并依据倾斜涡度发展理论,分析了强风暴的发展机制。结果表明:本次风暴是在以西北气流为主导的环流背景下产生的,低层增温,中高层降温和整层增湿是造成层结不稳定的重要原因。上游地区对流引发的干冷下沉气流沿太行山背风面下滑形成的下坡风是触发强风暴发生的直接动力机制。湿位涡分析表明,风暴发生区具有明显的等熵面倾斜,对流层中低层pm1<0区域,同时pm2>0,满足倾斜涡度发展的条件,对强风暴的发展具有一定指示性。风暴发展早期,其垂直方向次级环流可能与新雷暴的产生和雷暴的跳跃式传播有关。太行山地形引起的边界层风场的变化,包括下坡气流和边界层中尺度辐合线对风暴的触发、组织和移动发挥着重要作用。
By using all available observational data, such as satellite, Doppler radar images as well as routine observational data, and non-hydrostatic model MMSV3.5, a severe MCS （Mesoscale Convective System） occurred on 23 August 2001 in the North China was investigated. The evolutionary process and development mechanism of this MCS case was analyzed with emphasis on the orographic effect of Taihang Mountain on its development. The observational data show this severe storm occurred in the pattern of high-level northwest flow, the temperature increase in the lower troposphere descends in high-mid troposphere and the humidity enhanced in the whole troposphere induced the convective instability. The simulation results indicated that the downhill flow form Taihang Mountain is the key mechanism to initiate the convection. The characteristics of moist potential vorticity （MPV） show that the moist isentropes slant is the foundation of the convection, the vertical and horizontal components, i.e. Pm1 and Pm2 respectively, pm1 〈 0 and pm2 〉0 in the lower of troposphere are favorable condition for the development of MSC, it can serve as a powerful tools for the diagnosis and prediction of MCS. On the other hand, because the condition of MPV conservation can be destroyed possibly in the MCS process, for example the hydrostatic balance and the mass forcing induced by the precipitation et al. , can lead to MPV anomaly. In the early period of the MCS, the vertical second circulation can be an important mechanism to trigger new thunderstorm and conduce the storm spreading by jump model. The Taihang Mountain can change the wind field in boundary layer; include downhill flow, vertical shear of wind and mesoscale convergence line. As a result, it plays an important role in initiating, organization and movement of the storm.
出处
《气象学报》
CAS
CSCD
北大核心
2005年第4期504-515,i0004,共13页
Acta Meteorologica Sinica
基金
山东省气象局重点课题"中尺度模式业务系统及高性能计算环境应用"
"山东省中尺度数值预报系统的建立及应用"
山东省自然科学基金课题(Y2003E01)
