两类涡度矢量对四川盆地一次暴雨过程的分析应用

Analysis and Application of the Two Type Vorticity Vectors on a Heavy Rainfall in Sichuan Basin

利用WRF模式、NCEP 1°×1°再分析资料、常规观测资料对2013年6月29日至7月2日四川盆地的一次暴雨过程进行数值模拟和诊断分析。结果表明,此次暴雨过程是由高原低涡和西南低涡共同作用引起,西太平洋副热带高压(下称西太副高)西伸稳定在四川盆地,形成阻塞作用,导致高原低涡和西南低涡停滞不前。WRF模式能较好地模拟出降水的影响系统、降水落区以及强度。θe分析表明暴雨区位于高温高湿区内,暴雨区低层为对流不稳定区,中高层θe线密集且等θe面陡立,随着降雨的发生,对流不稳定能量释放,θe有所减弱。运用对流涡度矢量(CVV)和湿涡度矢量(MVV)对暴雨过程进行诊断分析后得出:CVV和MVV垂直分量的垂直积分及水平分布的正值带走向与暴雨落区相一致,且其大值中心与降水中心也有较好的对应。CVV和MVV垂直分量大值区的分布和发展与暴雨区的移动和发展较为一致,暴雨区从低层到高层一致的正值分布对暴雨发展具有指示意义。CVV和MVV垂直分量可以很好地指示四川盆地暴雨系统的发展和演变。

By using the WRF model,NCEP 1° ×1° reanalysis datasets and conventional observational data,numerical simulation and diagnostic analysis is performed for a heavy rainfall in Sichuan basin occurring during June 29th-July 2nd,2013. The results showed the heavy rainfall was caused by the interaction of plateau vortex and southwest vortex,and the blocking effect formed by the west pacific subtropical high westward extension and stabilize in Sichuan Basin led to stagnate of plateau vortex and southwest vortex. WFR model can better simulate the affecting system,precipitation area and strength of the precipitation. θeanalysis showed the heavy rainfall area was in the high temperature and high humidity area,and the lower level of the heavy rainfall area was convective instability area. Equivalent potential temperature was dense in the middle and upper level,and the isothermal surface of the equivalent potential temperature was steep. As the rainfall went on,the convective instability energy released,and the equivalent potential temperature declined. By using the convective vorticity vector（ CVV） and moist vorticity vector（ MVV）,diagnostic analysis result of the heavy rainfall showed the vertical integration of the CVV and MVV vertical component and the trend of the positive cincture of the horizontal distribution was consistent with the precipitation area,and the maximum center could better correspond to the precipitation center.The distribution and development of the maximum area of the CVV and MVV vertical component was consistent with the movement and development of the precipitation area,the coincident positive distribution from lowlevel to top level of the precipitation area was indicative to the heavy rainfall development. The CVV and MVV vertical component can well indicate the development and evolution of the heavy rainfall system in Sichuan Basin.