Tropopause Evolution in a Rapidly Intensifying Tropical Cyclone: A Static Stability Budget Analysis in an Idealized Axisymmetric Framework
Tropopause Evolution in a Rapidly Intensifying Tropical Cyclone: A Static Stability Budget Analysis in an Idealized Axisymmetric Framework
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DOI：
10.1175/jas-d-18-0097.1
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发表时间：
2019-01
影响因子：
3.1
通讯作者：
Patrick Durán;J. Molinari
中科院分区：
文献类型：
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作者：
Patrick Durán;J. Molinari
高层静稳定性（N2）变化会影响热带气旋（TC）中横向环流和位涡的演变。本文研究了模拟 TC 快速强化 (RI) 过程中的这些变化。在眼睛上方，对流层顶附近的 N2 减少，风暴中心的对流层顶冷点升高达 4 公里。在眼睛之外，N2 在冷点对流层顶之上显着增加，并且对流层顶仍接近其初始水平。预算分析表明，平流项（包括位温 θ 的差分平流和 N2 的直接平流）在整个对流层上部和平流层下部都很重要。这些术语在眼睛内尤其明显，它们破坏了冷点对流层顶附近和上方的层的稳定性。在眼睛外部，RI 期间会形成径向垂直环流，对流层顶下方有较强的流出，上方有较弱的流入。流出射流附近 θ 的差分平流作用提供了在流出最大值以下稳定和在上面失稳的作用力。流出最大值两侧的垂直风切变引起的湍流也改变了垂直稳定性剖面。同时，卷云冠层顶部的辐射冷却趋势通常会破坏对流层上部的稳定并稳定平流层下部。结果表明，湍流和辐射以及差分平流在热带气旋高层 N2 演化中发挥着重要作用。这些 N2 趋势可能对 TC 昼夜周期和 TC 中对流层顶层位涡演化产生影响。
Upper-level static stability (N2) variations can influence the evolution of the transverse circulation and potential vorticity in intensifying tropical cyclones (TCs). This paper examines these variations during the rapid intensification (RI) of a simulated TC. Over the eye, N2 near the tropopause decreases and the cold-point tropopause rises by up to 4 km at the storm center. Outside of the eye, N2 increases considerably just above the cold-point tropopause and the tropopause remains near its initial level. A budget analysis reveals that the advection terms, which include differential advection of potential temperature θ and direct advection of N2, are important throughout the upper troposphere and lower stratosphere. These terms are particularly pronounced within the eye, where they destabilize the layer near and above the cold-point tropopause. Outside of the eye, a radial–vertical circulation develops during RI, with strong outflow below the tropopause and weak inflow above. Differential advection of θ near the outflow jet provides forcing for stabilization below the outflow maximum and destabilization above. Turbulence induced by vertical wind shear on the flanks of the outflow maximum also modifies the vertical stability profile. Meanwhile, radiative cooling tendencies at the top of the cirrus canopy generally act to destabilize the upper troposphere and stabilize the lower stratosphere. The results suggest that turbulence and radiation, alongside differential advection, play fundamental roles in the upper-level N2 evolution of TCs. These N2 tendencies could have implications for both the TC diurnal cycle and the tropopause-layer potential vorticity evolution in TCs.