夏季青藏高原对流系统移出高原的气象背景场分析

利用1998-2004年6-8月共21个月的ISCCP对流路径集资料，结合NCEP/NCAR再分析资料和TRMM 3B42降水资料，采用合成统计分析方法，对夏季生成于青藏高原（高原）地区的对流系统进行了分类对比分析，目的在于研究各类高原对流系统动热力场的水平和垂直结构特征，探讨各类对流系统能否移出高原的气象背景场差异。结果表明，夏季高原对流系统主要生成于青藏高原中东部，存在两个高发中心。夏季高原对流系统按照对流系统的移动路径可以分为未移出高原、向南移出高原和向东移出高原3类。高原对流系统的移动、发展和生成源地没有直接关系，主要决定于气象背景场。当生成的高原对流系统上升运动强、水汽条件优越时，其强度不断增大，利于对流系统维持发展并移出高原，如果这类高原对流系统处于强西风气流控制下，容易向东移出高原，如受较强偏北风气流影响，则容易向南移出高原；而当生成的高原对流系统上升运动弱、水汽条件不理想时，其强度不断减弱，不利于对流系统发展移动，高原对流系统在高原区逐渐消亡。 

A study of the meteorological background of convective systems over the Tibetan Plateau

Convective systems originated from Tibetan Plateau are classified and their horizontal and vertical dynamic and thermodynamic structures are examined using the ISCCP data of tracks of convective systems, the NCEP/NCAR reanalysis data and the TRMM 3B42 from 1998 to 2004 during northern hemisphere summer (June-August). The results reveal that convective systems mainly form over the southeastern Tibetan Plateau. Convective systems are classified into three categories:Staying over the Plateau and southward and eastward moving out of the Plateau. The movement and development of convective systems are determined by surrounding environmental meteorological conditions. The convective systems with strong upward motion and plenty of water vapor may move out of the Plateau, whereas those with weak upward motion and small amount of water vapor stay and dissipate over the Plateau. The southward and eastward movements of convective systems are steered by surrounding northerly and westerly winds.