LAUSR

A three-dimensional transformed Eulerian-mean (3D TEM) equation under a non-hydrostatic and non-geostrophic assumption is deduced in this study. The vertical component of the 3D wave activity flux deduced here is the primary difference from previous studies, which is suitable to mesoscale systems. Using the 3D TEM equation, the energy propagation of the inertia–gravity waves and how the generation and dissipation of the inertia–gravity waves drive the mean flow can be examined. During the mature stage of a heavy precipitation event, the maximum of the Eliassen–Palm (EP) flux divergence is primarily concentrated at the height of 10–14 km, where the energy of the inertia–gravity waves propagates forward (eastward) and upward. Examining the contribution of each term of the 3D TEM equation shows that the EP flux divergence is the primary contributor to the mean flow tendency. The EP flux divergence decelerates the zonal wind above and below the high-level jet at the height of 10 km and 15 km, and accelerates the high-level jet at the height of 12–14 km. This structure enhances the vertical wind shear of the environment and promotes the development of the rainstorm.摘 要在非地转非静力平衡条件下, 我们成功推导出适用于中小尺度的三维EP通量方程. 其中, 与前人工作的最大区别是在于推导得到的三维EP通量的垂直分量. 利用三维EP通量方程, 我们研究了惯性重力波的能量传播问题以及惯性重力波对背景流场的影响. 我们选取四川地区一次暴雨过程为例. 分析发现在暴雨的成熟阶段, 最大的EP通量散度位于高空10-14km的位置, 此处有惯性重力波向前向上传播. 将EP通量进一步分解后分析发现, EP通量散度是对背景流场的主要贡献项. EP通量散度能够使得高空急流的上下两侧U风速减速, 并且加速高空急流, 从而增强高空急流上下两侧的垂直风切, 进一步促进了暴雨发展.