青藏高原东侧陡峭地形对一次强降水天气过程的影响

Impact of the Steep Terrain of Eastern Qinghai-Xizang Plateau on the Genesis and Development of Extreme Heavy Rainfall Event

利用高分辨率中尺度模式分析资料,研究了青藏高原东侧陡峭地形对一次暴雨天气发生发展的影响。结果显示,青藏高原地形对大气环流的动力阻挡作用形成了本次暴雨过程的水汽输送通道,青藏高原东侧陡峭地形结构造成了四川西北部和黄河上游的强水汽辐合中心,并使低层高能舌和能量锋区位于海拔较低的四川盆地,在四川盆地对流层低层建立起位势不稳定层结。青藏高原东侧陡峭地形结构引起了低层偏东气流强烈的垂直上升运动,最强的垂直上升运动出现在东西风垂直切变与陡峭地形交汇处,激发不稳定能量释放,促使强对流猛烈发展,暴雨过程中高原东侧还有一个中尺度涡旋的发生发展相伴。青藏高原东侧暴雨区最显著的热力特征是高温高湿区域仅出现在对流层低层,最显著的动力特征是强涡度柱也仅出现在对流层低层。

Using the high resolotion mesoscale model analysis data, the impact of the complex mesoscale terrain on the east side of the Qinghai-Xizang Plateau to the genesis and development of the heavy rainfall event was analyzed. The result shows that the dynamic blocking effect of the Qinghai-Xizang Plateau terrain on atmospheric circulation form the moisture transfer channel over the region of heavy rain scenario occurring and a strong vapor convergence center in the northwest Sichuan and the upper reach of Yellow River. The terrain structure on the east side of Qinghai-Xizang Plateau and the accumulation of vapor in Sichuan Basin also form the high energy tongue and energy front in the lower layer and the potential instability energy in the lower troposphere of Sichuan Basin. The steep terrain on the east side of Qinghai-Xizang Plateau strengthens the ascendant motion. The strongest updraft movement occurred in the convergence area of the vertical shear of east and west wind and the steep landform, stimulating the release of the unsteady energy and rapid development of the strong convection. The process is also accompanied by a mesoscale vortex on the east side of the Plateau. The most significant thermal and dynamical features is very different with mold rain with the high-temperature and high-humidity only appearing in the lower troposphere and strong vorticity column only appearing in the lower troposphere.