Balanced and Radiating Wave Responses to Diurnal Heating in Tropical Cyclone–Like Vortices Using a Linear Nonhydrostatic Model
Balanced and Radiating Wave Responses to Diurnal Heating in Tropical Cyclone–Like Vortices Using a Linear Nonhydrostatic Model
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DOI：
10.1175/jas-d-18-0361.1
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发表时间：
2019-08
影响因子：
3.1
通讯作者：
Rebecca C. Evans;D. Nolan
中科院分区：
文献类型：
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作者：
Rebecca C. Evans;D. Nolan
热带气旋卷云冠层的日变化是一个有据可查的现象。虽然早期的研究将卷云冠层区域的DC与眼壁对流强度的DC联系起来，但后来的研究认为这是对卷云冠层辐射DC的直接响应。在这项研究中，一个理想化的线性模型被用来研究在何种程度上线性动态可以捕获的DC TC，特别是平衡和辐射响应昼夜加热之间的过渡。该模型的热强迫是物理动机的非绝热加热输出从一个现实的模拟，说明了存在的DC在湿对流加热和辐射加热的眼壁，和DC在卷云冠层的辐射加热。这项研究发现，在眼壁加热的直流电产生的响应，是限制在RMW内部的内核中的高惯性稳定性。卷云冠层辐射加热的直流电在整个气旋中产生响应。低频率响应，昼夜和半日频率，在整个气旋的大部分平衡。在日出和日落时产生的周期小于8小时的高频波可以向外和向下辐射。这些结果表明，日响应是平衡的，在大多数的TC和起源于卷云冠层，而不是眼壁。卷云冠层垂直运动中的直流电似乎也起源于卷云冠层。
The diurnal cycle (DC) in the cirrus canopy of tropical cyclones (TCs) is a well-documented phenomenon. While early studies linked the DC in the area of the cirrus canopy to a DC in the strength of eyewall convection, later studies considered it a direct response to the DC of radiation in the cirrus canopy. In this study, an idealized linear model is used to examine the extent to which linear dynamics can capture the DC in TCs, in particular the transition between balanced and radiating responses to diurnal heating. The model heat forcing is physically motivated by the diabatic heating output from a realistic simulation, which illustrates the presence of a DC in moist convective heating and radiative heating in the eyewall, and a DC in radiative heating in the cirrus canopy. This study finds that the DCs of heating in the eyewall yield a response that is restricted to inside the RMW by the high inertial stability in the inner core. The DC of radiative heating in the cirrus canopy yields a response throughout the entire cyclone. Lower-frequency responses, of diurnal and semidiurnal frequency, are balanced throughout much of the cyclone. High-frequency waves with periods under 8 h, created at sunrise and sunset, can radiate outward and downward. These results indicate that diurnal responses are balanced in the majority of a TC and originate in the cirrus canopy, instead of the eyewall. The DC in cirrus canopy vertical motion also appears to originate in the cirrus canopy.