一次强暴雨形成的动力机制

分析了1998年7月武汉强暴雨的天气演变特征，并从理论上探讨了强暴雨形成的动力机制。结果表明：低空急流先于暴雨生成，暴雨最强时低空急流也最强；高空急流入口区右侧及低空急流左侧非热成风梯度的存在，使得中尺度不稳定波的波振幅出现空间不稳定现象，高空急流右侧不稳定波的波振幅和低空急流左侧不稳定波的波振幅向暴雨区增加，暴雨区恰为这两支波叠加后振幅最大的区域，高低空急流耦合下的非热成风、中尺度对流-对称不稳定可能是这类强暴雨产生的动力原因之一。

Dynamic Analysis on Formation of a Torrential Rain

The paper analyses the developing characteristic of a torrential rain in Wuhan,and theoretically discusses the dynamic mechanism of the torrential rain.The results show that the low-level jet(LLJ) occurred before the torrential rain,and when the torrential rain is the strongest,the LLJ is also the strongest.The existence of non-thermal wind gradients on the right side of the entrance region of the upper level jet (ULJ) and the left of the LLJ,leads to the unstable amplitude of mesoscale waves.The unstable amplitude increases towards the torrential rain area,which tallies with the maximum amplitude area of waves due to the overlapping of the two unstable waves.Under the circumstance of the coupling of the upper and low level jets,the non-thermal wind mesoscale convection-symmetric instability might be one of dynamic mechanisms resulting in torrential rain.