东北冷涡内部中尺度涡旋引起的冰雹天气数值模拟

Numerical simulation on hail weather caused by meso-scale vortex inside cold vortex over northeastern China

利用NCEP格点资料模拟2011年8月21日沈阳地区的冰雹天气过程,结合机场自动观测数据、多普勒雷达资料和卫星云图等分析冰雹的形成机制。结果表明:此次冰雹天气是由冷涡内部的中尺度涡旋引起的,卫星云图上的中尺度云团是中尺度涡旋的产物;0℃等温线位于600 hPa,-20℃位于450 hPa附近,两者之间厚度为2 km左右;冰雹发生前,斜升气流的最大上升速度为20 m·s-1以上,水分累积区位于0℃层以上,保证了水分累积区均由过冷水滴组成;高层干冷空气倾斜下侵到中低层的暖湿空气中,对强对流的发生发展起到了至关重要的作用;低层MPV1为强对流提供对流不稳定机制,中层MPV2为强对流提供了对称不稳定机制,高层两种不稳定共存,均为对流发展贡献力量;对流有效位能积累和释放随时间的演变对冰雹的出现有一定的指示意义;10:30多普勒雷达图显示回波强度随高度增强,速度图上存在西南低空急流,有利于对流的发展。

Based on the NCEP grid data, a hail weather process on August 21,2011 in Shenyang region was simu- lated and its formation mechanism was analyzed using the automatic observation data collected at the airport, Doppler radar data and satellite image. The results show that the hall weather is caused by mesoscale vortex of cold vortex over northeastern China, so is mesoscale cloud cluster on the satellite cloud images. The 0℃（3 and - 20 ℃ i- sothermal lines are located in 600 hPa and near 450 hPa, respectively, and the thickness between them is about ^-1 2 km. Before the hall occurs, the maximum ascending speed of obliquely ascending airflow is more than 20 m. s and water vapor accumulation region is located in the layer above 0 ~C, which ensures that the water accumulated area consists of super cooled water droplet. The upper dry cold air invades into the warm-wet air of middle-low level, which is important to convective occurrence and development. The MPV1 in the low level provides the con- vective instability mechanism for strong convection; the MPV2 in the middle level is for symmetric instability mechanism;two unstable mechanisms coexist in the high level and both contribute to the development of convec- tion. The evolution of convective available potential energy accumulation and release with the time is indicative to hail. At 10：30, the echo intensity increases with the height on Doppler radar map. There is southwest low level jet on the velocity map. Both are favorable to the development of convective.