涡度收支与潜热释放对西南低涡形成的作用

The influence of low-level jet and latent heat release on the formation of a southwest vortex

利用中尺度WRF模式对2008年6月30日—7月1日生成于川东南地区的一个西南低涡的发生发展过程进行了数值模拟研究。模拟结果显示低涡首先出现在850 h Pa上,几个小时后700h Pa上才有低涡生成,850 h Pa低涡的形成与西南低空急流有着密切的联系。通过ω方程的诊断分析表明,涡度的水平平流项和辐散项对850 h Pa低涡的形成起主要作用,而潜热释放对850 h Pa低涡的形成作用不大;潜热加热是700 h Pa气流不断辐合从而形成低涡的主要因子。干敏感性试验研究进一步证实了潜热释放对850 h Pa低涡的影响不明显,但是会导致700 h Pa上气旋性的切变加强辐合从而形成低涡。

Using mesoscale simulation WRF model,the formation and development of a southwest vortex occurred over Sichuan province on June 30 and July 1,2008 were investigated. The results indicated that the southwest vortex primarily emerged at 850 h Pa and then formed at 700 h Pa after several hours. The formation of the southwest vortex at 850 h Pa was directly connected with low-level jet. The diagnostic analysis of ω equation show ed that the horizontal advection of vorticity and divergence mainly influenced the formation of the southw est vortex at 850 h Pa w hile latent heat release w as not important to its genesis. The results also indicated that the latent heating w as the key factor for the formation of the southw est vortex at 700 h Pa. The dry sensitive experiment further confirmed that latent heat release had little influence on the southw est vortex at 850 h Pa,but it caused strong convergence of cyclonic shear circulation and finally formed the vortex at 700 h Pa.