青藏高原东北侧突发性暴雨特征综合分析

Comprehensive Analysis on Abrupt Torrential Rains in Northeast Tibet Plateau

对1970-2007年发生在青藏高原东北侧陕西的突发性暴雨研究发现,其夜间降水特点明显,对流层中层较强的偏南气流是突发性暴雨水汽输送贡献最大者和低层辐合的主要动力来源。偏南气流北伸的位置决定突发性暴雨落区偏南或偏北,300hPa一致的纬向12～20m·s-1强风速带为突发性暴雨提供高层抽吸作用。上述两点对突发性暴雨落区有一定的预报指示意义。云图分析显示,突发性暴雨多有中尺度云团配合,上升运动最大值的高度层与突发性暴雨落区地域位置有关。

A study on abrupt torrential rains in Shaanxi in the northeast of Tibet plateau from 1970 to 2007 indicates that night precipitation is significant and the southerly airflow in mid-troposphere is the main contributor of water vapor transferring to the torrential rain and the pivotal dynamic source of low-level convergence.Position of northward moving of southerly airflow is closely related to precipitation area.Consistent 12-20 m·s-1 strong latitudinous wind belt provides the torrential rain with pumping effects.The above two points are predictive to rainfall area.Cloud image analysis shows that the abrupt torrential rain is in most cases accompanied by MESO-scale cloud clusters,while level of maximum upward motion corresponds with rainfall area.