涡动相关仪探测台风边界层动量通量特征分析

CHARACTERISTICS OF MOMENTUM FLUX IN TYPHOON BOUNDARY LAYER USING EDDY COVARIANCE SYSTEM

关键词:  动量通量  台风“利奇马”  涡动相关仪  边界层  多尺度分析

Key words:  momentum flux  Typhoon Lekima  Eddy covariance system  boundary layer  multiscale analysis

摘要:

台风的发展维持受制于自身(内部结构)及与下垫面间的通量传输过程，利用台风“利奇马”登陆前后的涡动相关仪观测数据，分析台风过境前后地面要素变化及动量通量特征。分析结果表明：台风过境期间，地面气象要素在短时间内出现急剧的变化，动量通量在台风登陆过程中显示出“三峰”的结构，对应的摩擦速度随风速的变化以10 m/s为分界线，低风速下呈现明显的正相关性，高风速时则慢慢转为持平甚至回落；能谱分析中，峰值主要存在于0.000 2 Hz和0.06 Hz的位置上，另有一位于0.001 Hz外的较弱峰值；能量贡献上，大尺度系统占据主导作用，但中尺度对流系统与湍流尺度运动在能量贡献中同样不可忽视。

Abstract:

The development and maintenance of tropical cyclones are subject to the flux exchange process within itself (internal structure) and with the underlying surface. This paper uses 36-hour observational data collected by the Eddy Covariance System during the landing of Typhoon Lekima. The characteristics of ground parameters changes and momentum flux transmission are analyzed. The results show that during the landing of Typhoon Lekima, the ground parameters of the observation fields change significantly within a short period of time. The momentum flux shows a three-peak structure during the landing of the typhoon. The corresponding friction velocity changes with wind speed. It shows a clear positive correlation at a wind speed lower than 10 m/s, and it slowly turns to be flat or even falls back at a higher wind speed than 10 m/s. In the energy spectrum, the peaks mainly exist at 0.000 2 Hz and 0.06 Hz, and there is a weaker peak at 0.01 Hz. In terms of energy contribution, large-scale systems play a dominant role, while mesoscale convective systems and turbulences also contribute a lot and thus cannot be ignored.