Role of eyewall and rainband eddy forcing in tropical cyclone intensification
Role of eyewall and rainband eddy forcing in tropical cyclone intensification
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DOI：
10.5194/acp-19-14289-2019
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发表时间：
2019-11
影响因子：
6.3
通讯作者：
P. Zhu;B. Tyner;Jun A. Zhang;E. Aligo;S. Gopalakrishnan;F. Marks;A. Mehra;V. Tallapragada
中科院分区：
文献类型：
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作者：
P. Zhu;B. Tyner;Jun A. Zhang;E. Aligo;S. Gopalakrishnan;F. Marks;A. Mehra;V. Tallapragada
抽象的。虽然湍流通常被认为是与行星边界层（PBL）有关的流动特征，但由云过程产生的强烈湍流混合也存在于热带气旋（TC）的PBL上方的眼壁和雨带中。边界层上方的云内湍流与眼壁和雨带中对流要素的发展密切相关，并构成了TC一次环流和二次环流演变的一部分非对称涡动强迫。在这项研究中，我们表明，飓风天气研究和预报（HWRF）模型，用于TC预测的业务模式之一，是无法产生适当的次网格尺度（SGS）的涡动强迫PBL以上，由于缺乏考虑强烈的湍流混合所产生的眼壁和雨带云。在垂直对流混合方案中引入云内对流混合参数化显著提高了HWRF模型预测过去几次主要飓风强度快速变化的能力。虽然分析表明，SGS的涡动强迫PBL以上的模式分辨的涡动强迫只有约五分之一，模拟TC涡的内核结构，二次翻转环流，和模式分辨的涡动强迫表现出很大的依赖于参数化的SGS涡动过程。结果强调了眼壁和雨带SGS涡动强迫对TC强化数值预报的重要性，包括在当前业务模式分辨率下的快速强化。
Abstract. While turbulence is commonly regarded as a flow feature pertaining to the planetary boundary layer (PBL), intense turbulent mixing generated by cloud processes also exists above the PBL in the eyewall and rainbands of a tropical cyclone (TC). The in-cloud turbulence above the PBL is intimately involved in the development of convective elements in the eyewall and rainbands and consists of a part of asymmetric eddy forcing for the evolution of the primary and secondary circulations of a TC. In this study, we show that the Hurricane Weather Research and Forecasting (HWRF) model, one of the operational models used for TC prediction, is unable to generate appropriate sub-grid-scale (SGS) eddy forcing above the PBL due to a lack of consideration of intense turbulent mixing generated by the eyewall and rainband clouds. Incorporating an in-cloud turbulent-mixing parameterization in the vertical turbulent-mixing scheme notably improves the HWRF model's skills in predicting rapid changes in intensity for several past major hurricanes. While the analyses show that the SGS eddy forcing above the PBL is only about one-fifth of the model-resolved eddy forcing, the simulated TC vortex inner-core structure, secondary overturning circulation, and the model-resolved eddy forcing exhibit a substantial dependence on the parameterized SGS eddy processes. The results highlight the importance of eyewall and rainband SGS eddy forcing to numerical prediction of TC intensification, including rapid intensification at the current resolution of operational models.