南海台风边界层湍流小波分析

WAVELET ANALYSIS OF TURBULENCE IN BOUNDARY LAYER OF TYPHOON IN SOUTH CHINA SEA

利用小波变换(WT)对香港天文台飞机观测台风“妮妲”(1604)资料进行分析,研究在不稳定、不均匀的台风边界层中湍流涡旋的垂直传输作用。在0.1~5 Hz惯性子区内横风和顺风分量功率谱密度能较好符合-5/3幂律。小波分析显示:横风的小波功率谱峰值集中在1 km之下,顺风分量的小波功率谱峰值集中在1~6km之间;眼区动量通量的主要贡献尺度为2.3 km,眼区外主要贡献尺度在1~2 km,中低层为较小尺度(<1.0km);湍流功能(TKE)的生成尺度主要集中在4 km之下。这项研究定量描述了南海北部台风边界层各个区域湍流结构的差异特征,讨论了对台风边界层通量参数化的可能影响。

In the present study,wavelet transform is used to analyze the data of Typhoon Nida(1604)observed by an aircraft of the Hong Kong Observatory to study the vertical transport by turbulent vortices in the unstable and inhomogeneous typhoon boundary layer.The power spectral density of the crosswind and along-wind components fits in well with the-5/3 power law in the inertial sub-range within 0.1~5 Hz.Wavelet analysis shows that the peak of the wavelet power spectrum of the crosswind is concentrated below 1 km,and the peak of the wavelet power spectrum of the along-wind component is concentrated between 1 and 6 km.Momentum flux has a major contribution scale of 2.3 km in the eye area,a major contribution scale of 1~2 km outside the eye area,and a smaller scale(<1.0 km)on the middle and bottom layers.The production of turbulence kinematic energy is mainly contributed on the scale below 4 km.This study illustrates quantitatively the different turbulence characteristics in different regions of the typhoon boundary layer over the north South China Sea,and discusses the possible influence of the results on the parameterization of turbulence processes in the typhoon boundary layer.