摘要
观测发现热带气旋(TC)边界层中存在龙卷尺度涡旋(TSV),其引起的相关阵风对近地面具有强烈影响.利用WRF-ARW模型,通过对飓风Earl(2010)进行高分辨率的数值试验模拟,分析了TC边界层龙卷尺度涡旋的时空分布特征以及发生发展的可能原因.Earl发展增强过程中,TSV数量随着Earl强度的增强而增加,尤其在最强期间表现最为活跃,一方面TC的增强提供了更强的背景场使得TSV更易生成,另一方面更强的背景场使得长生命期的TSV增加,每一时刻同时存在的TSV也就更多.TSV生成区域随Earl的发展从垂直风切左侧逐渐集中至逆风切左侧,且始终位于RMW内侧近地层次级环流上升支和最大垂直涡度位置附近,这里通常满足垂直切变和水平切变不稳定的必要条件,TSV涡度收支分析的结果表明,对TSV生成发展起主要贡献的是与水平风水平切变相关的拉伸项以及与垂直切变相关的扭转项,这意味着TSV的生成与发展可能与垂直切变不稳定和水平切变不稳定有关.
Observations have revealed the presence of tornado-scale vortices(TSVs)within the boundary layer of tropical cyclones(TCs),which significantly impact near-surface gustiness.Based on Weather Research and Forecasting Model-Advanced Research WRF(WRF-ARW),a high-resolution numerical experiment in simulating Hurricane Earl(2010)is conducted to analyze the activity characteristics of TSVs in boundary-layer.During the strengthening process of Earl,the number of TSVs increases with the intensification of Earl,especially during its peak.On one hand,the strengthening of the tropical cyclone(TC)provides a stronger background field,making it easier for TSVs to form.On the other hand,the stronger background field leads to an extended lifespan for TSVs,resulting in a higher number of concurrent TSVs at any given moment.The area that TSV generating gradually shifts from the left side of the vertical wind shear to the up-shear left as Earl develops,near the secondary circulation updraft and the maximum vertical vorticity,where often meets the necessary conditions of unstable vertical and horizontal wind shear.The results of TSV vorticity budget analysis further indicate that the stretching term associated with horizontal wind shear and the tilting term associated with vertical wind shear are important factors in the generation and development of TSVs,which implies that the generation and development of TSV may be related to vertical shear instability and horizontal shear instability.
作者
周玥滢
方娟
Zhou Yueying;Fang Juan(Key Laboratory of Mesoscale Severe Weather,Ministry of Education,and School of Atmospheric Sciences,Nanjing University,Nanjing,210023,China)
出处
《南京大学学报（自然科学版）》
CAS
CSCD
北大核心
2024年第2期230-243,共14页
Journal of Nanjing University（Natural Science）
基金
国家自然科学基金(42175004)
关键词
热带气旋
龙卷尺度涡旋
垂直切变
水平切变
tropical cyclones
tornado-scale vortex
vertical shear
horizontal shear
