湿位涡守恒条件下西南涡的发展

THE DEVELOPMENT OF SOUTHWEST VORTE IN CONSERVATION OF MOIST POTENTIAL VORTICITY

运用高分辨率数值预报模式 (HIRLAM)模拟了一次中国西南地区在多种活跃天气系统影响下 ,西南涡的发展过程。分析了东亚季风、青藏高压、地形等多种尺度与不同高低空环流形势配合以及在湿位涡守恒条件下对流发展时 ,潜热及不稳定能量的释放 ,对中尺度涡旋和强对流发生发展的作用 ,探讨了西南涡和局地降水增强与消亡的成因与理论 。

By using the high resolution limited area model (HIRLAM) and real data from the T106 model, the development of Southwest China vortex associated with the precipitation process over Jinfo Mountains by affection of South China Sea monsoon is simulated. The affections of South China Sea monsoon, South Asia high, topography lifting, and conservation of moist potential vorticity on the development of vortex and strong convection are discussed in detail.The results show that all these could affect the precipitation process,but here we emphasize that their properly vertical structure will play a more important role. As shown in the results,the Meiyu front is formed by the confrontation between the South China Sea monsoon and the cold air from the north in the low.When this front has been properly overlapped with South Asia high,the intensified convection will be excited from the southwest vortex center existing in the front and causes the precipitation.But along with the more cold air from the north moving into this area in the late phase,the subtle balance will be destroyed by this motion.The precipitation stopped even if the souhtwest vortex still existed in the low.