Statistical Analysis of Convective Updrafts in Tropical Cyclone Rainbands Observed by Airborne Doppler Radar
Statistical Analysis of Convective Updrafts in Tropical Cyclone Rainbands Observed by Airborne Doppler Radar
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DOI：
10.1029/2021jd035718
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发表时间：
2022-03
期刊：
影响因子：
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通讯作者：
Nicholas J Barron;A. Didlake;P. Reasor
中科院分区：
文献类型：
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作者：
Nicholas J Barron;A. Didlake;P. Reasor
利用10年的机载多普勒雷达观测资料，研究了热带气旋雨带中对流上升气流的运动学和反射率结构。开发了一种自动算法来识别12个飓风强度TC中最强的雨带上升气流。然后，对选定的上升气流的频率、半径、方位角位置（相对于200-850 hPa环境风切变）、结构特征和二次环流（径向/垂直）流型进行集体分析。雨带上升气流随着半径的增大而变深变强。波数-1的不对称性出现，表明在TC的下切变（上切变）象限，上升气流更频繁（更少）和更深（更浅）。在下切变象限中，上升气流主要有in-up-out或in-up-in次级环流模式。最常见的模式是in-up-out环流，并且具有最深的上升气流和反射率塔。上升气流通常具有出-上-入或入-上-入模式。上升气流环流的径向流很大程度上遵循涡尺度径向流切变诱导的不对称性，在下切变（上切变）象限中增加了低空流入（流出）和中层流出（流入）。假设对流尺度环流在上升气流底部和顶部高度受到涡旋尺度径向流的显著影响。对流生命周期的其他过程，例如由于低层下降气流增加而导致的老化对流上升气流的自下而上衰减，可以影响基本高度，从而影响上升气流环流的基本径向流。这项研究中提出的结果支持了以前的文献中关于成熟，剪切TC中有组织雨带对流的对流尺度模式。
Ten years of airborne Doppler radar observations are used to study convective updrafts' kinematic and reflectivity structures in tropical cyclone (TC) rainbands. An automated algorithm is developed to identify the strongest rainband updrafts across 12 hurricane‐strength TCs. The selected updrafts are then collectively analyzed by their frequency, radius, azimuthal location (relative to the 200–850 hPa environmental wind shear), structural characteristics, and secondary circulation (radial/vertical) flow pattern. Rainband updrafts become deeper and stronger with increasing radius. A wavenumber‐1 asymmetry arises, showing that in the downshear (upshear) quadrants of the TC, updrafts are more (less) frequent and deeper (shallower). In the downshear quadrants, updrafts primarily have in‐up‐out or in‐up‐in secondary circulation patterns. The in‐up‐out circulation is the most frequent pattern and has the deepest updraft and reflectivity tower. Upshear, the updrafts generally have out‐up‐in or in‐up‐in patterns. The radial flow of the updraft circulations largely follows the vortex‐scale radial flow shear‐induced asymmetry, being increased low‐level inflow (outflow) and midlevel outflow (inflow) in the downshear (upshear) quadrants. It is hypothesized that the convective‐scale circulations are significantly influenced by the vortex‐scale radial flow at the updraft base and top altitudes. Other processes of the convective life cycle, such as bottom‐up decay of aging convective updrafts due to increased low‐level downdrafts, can influence the base altitude and, thus, the base radial flow of the updraft circulation. The findings presented in this study support previous literature regarding convective‐scale patterns of organized rainband convection in a mature, sheared TC.