【摘要】 利用NCEP分析资料、WRF模式预报场、实况场、FY-2C云顶亮温TBB资料,对2009年5月16日发生在陕西境内的强对流天气过程进行诊断发现:此次强对流天气过程是在高空低槽和地面切变线的有利形势下产生的。对流层中上部高位涡干冷空气沿陡峭等熵面下滑,西北气流穿过等压线下沉,把高位涡向东向下输送,高位涡气块垂直向下伸展,使得对流层中低层的位涡迅速增大,上升运动增强造成强对流天气过程。强对流天气发生在地面总温度场锋区,干暖盖的存在和维持有利于不稳定能量聚积,对流有效位能、SI指数随时间的变化对于此次强对流天气过程有很好的指示意义。低层辐合上升触发对流发生,较强的上升运动与风垂直切变相互作用,有利于对流系统的增强。更多还原

【Abstract】 Strong convection is characterized by the small spatial scale,short duration and sudden occurrence.Strong convective weather induces disasters and results in the losses of life and property.Chinese meteorologists have conducted a great deal of researches on the mechanism and characteristics of strong convective weather in northwest China.However,it is still difficult to forecast strong convective weather.It is necessary for meteorologists to continue their studies on strong convective weather.In this paper,we focus on a continuous 8-day rainy weather occurred in Shaanxi Province from May 8 to 15,2009.A strong convective weather process occurred over the Loess Plateau of China on May 16th.Many studies reveal that there is often a low-level shear line or vortex before a strong convective weather occurs.However,this process does not occur under an obvious low-level shear line or vortex,but northerly winds.So it is difficult to forecast a severe short-duration convective weather.We tried to reveal the formation mechanism behind such events and provide the useful forecast ideas for future similar weather based on the NCEP analysis data,Weather Research Forecast(WRF) model forecasting data,observed data and Black Body Temperature(TBB) data by using common diagnostic analysis techniques.Results indicate that on May 16th there were two characteristics in the severe convective weather:Firstly,with upper-level low trough and the shear line over the ground,a strong convective weather occurred after rainy weather for several days.Secondly,observed data shows that there was no shear line between northerly wind and southerly wind at 850 hPa and 700 hPa,there was a cyclonic curvature between northerly wind and northwesterly wind over north and central Shaanxi.Moreover,atmosphere was relatively wet at 850 hP,and the near-surface atmosphere was stable.The upper-level low trough and the ground shear line afford a favorable weather situation for the development of meso-scale system.Strong convective instability and strong upward motion were conducive to the formation and maintenance of meso-scale convective cloud clusters.Synoptic scale systems of strong convective weather occurrence and precipitation were forecasted successfully by WRF model,so its forecasting data can be used to study the physical mechanism of the formation of strong convection weather.Based on the WRF model forecasting data and per hour data from Automatic Weather Station in Shaanxi Province,thermal and dynamic conditions,such as moist static temperature,convective available potential energy,SI index,divergence,vertical wind shear and updraft,are analyzed.High-energy area of moist static temperature represents the unstable,warm and humid air mass,but low-energy area represents the cold-dry air mass.更多还原