基于大涡模拟的台风边界层龙卷尺度涡旋对近地面阵风的影响研究

Strong gusts are closely associated with wind damage caused by typhoons. The characteristics of near-surface gusts and its relationship with tornado-scale vortices still need to be further studied. This proposal is aimed to simulate fine-scale structures of the typhoon boundary layer on the full ocean with a horizontal resolution of 37 m by using the mesoscale WRF model combined with the large eddy simulation technology (WRF-LES). The characteristics of near-surface gusts and gust factors will be studied in more details based on the features of tornado-scale vortices in the typhoon boundary layer. Three main objectives of this proposal are to: (1) understand the distribution characteristics of near-surface gusts and gust factors, based on fine-scale structures of typhoon boundary layer simulated by WRF-LES; (2) analyze the temporal and spatial distribution characteristics, active background conditions, evolution laws of tornado-scale vortices in the boundary layer, and their relationships with local winds; (3) investigate the relationships among the tornado-scale vortices, gusts and gust factors, also reveal the influence mechanism of tornado-scale vortices on near-surface gusts. This study will greatly improve our understanding of the structure and evolution characteristics of the tornado-scale vortices, and provide reference and theoretical foundation for the gust forecast in coastal areas under the influence of typhoons.

台风影响下的强阵风与灾害紧密联系，而近地面极端阵风的分布特征，及其与边界层龙卷尺度涡旋的关系仍不清楚。本项目拟采用WRF（Weather Research and Forecasting）模式结合边界层大涡模拟（Large Eddy Simulation, LES）技术，采用最高37 m水平分辨率模拟台风边界层精细风场结构，结合台风边界层龙卷尺度涡旋的活动特点深入理解近地面阵风及阵风因子的特征。为此，（1）模拟台风边界层精细风场结构，认识台风近地面阵风及阵风因子的分布特征；（2）探究边界层内龙卷尺度涡旋的时空分布特征、活跃的背景条件、演变规律及其和局地大风的关系；（3）结合边界层龙卷尺度涡旋的特征，分析其与阵风及阵风因子的关系，揭示龙卷尺度涡旋对近地面阵风的影响机制。预期目标完成后，不仅能深化理解龙卷尺度涡旋的结构和演变特征，同时也为沿海地区的台风阵风预报提供参考及理论依据。

在国家自然科学青年基金的资助下（2020-2022年期间），项目以理解台风内核区表面阵风和阵风因子分布特征为目标，基于最高37 m水平分辨率的大涡模拟结果，以台风边界层内的精细结构特征为切入点，重点揭示了台风边界层龙卷尺度涡旋对近地面阵风和阵风因子的影响。围绕项目研究目标，紧跟研究任务展开研究，已发表学术论文10篇；以项目主持人为第1作者发表SCI 论文共 2篇。项目的研究结果归纳如下：①揭示了湍流灰区尺度（100m – 1km）至大涡尺度（< 100m）水平分辨率对台风边界层涡旋尺度结构和边界层精细结构的影响。②基于大涡模拟，揭示了台风内核区近地面阵风和阵风因子的分布特征。③首次提出了边界层龙卷尺度涡旋和边界层滚涡的可能转换关系，为台风边界层精细结构供了新的理论依据和认识。④从台风内部环流系统的角度，解释了台风近地面极端阵风和阵风因子的成因。通过研究深化理解龙卷尺度涡旋的结构和演变特征，揭示了台风边界层内龙卷尺度涡旋对极端阵风和阵风因子的影响。着眼于台风边界层精细结构特征，解释了台风近地面阵风及阵风因子的分布特征，为台风的阵风预报提供理论基础。.