The Roles of Asymmetric Inflow Forcing Induced by Outer Rainbands in Tropical Cyclone Secondary Eyewall Formation
The Roles of Asymmetric Inflow Forcing Induced by Outer Rainbands in Tropical Cyclone Secondary Eyewall Formation
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DOI：
10.1175/jas-d-12-084.1
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发表时间：
2013-03
影响因子：
3.1
通讯作者：
X. Qiu;Z. Tan
中科院分区：
文献类型：
--
作者：
X. Qiu;Z. Tan
摘要本文分析了热带气旋理想化云分辨模拟中的二次眼壁形成过程。特别是，研究了边界层对外部雨带(ORB)非对称入流强迫的非平衡响应，以了解在SEF的早期阶段驱动初级眼壁外持续对流的机制。增强对流的方位向分布是高度不对称的，但却是规则的，一般是沿着从球体下风部分开始的半圆形。结果表明，球体中部和下风部分的下降径向流入在边界层中启动/维持了一股强的流入。后者能够穿透内核区，使径向速度梯度变陡，加强收敛。因此，温暖而潮湿的空气在领头不断地上升……
AbstractThis study analyzes the secondary eyewall formation (SEF) process in an idealized cloud-resolving simulation of a tropical cyclone. In particular, the unbalanced boundary layer response to asymmetric inflow forcing induced by outer rainbands (ORBs) is examined in order to understand the mechanisms driving the sustained convection outside the primary eyewall during the early phase of SEF.The enhancement of convection in the SEF region follows the formation and inward contraction of an ORB. The azimuthal distribution of the enhanced convection is highly asymmetric but regular, generally along a half circle starting from the downwind portion of the ORB. It turns out that the descending radial inflow in the middle and downwind portions of the ORB initiates/maintains a strong inflow in the boundary layer. The latter is able to penetrate into the inner-core region, sharpens the gradient of radial velocity, and reinforces convergence. Consequently, warm and moist air is continuously lifted up at the lead...