台风“珍珠”登陆期间动量通量的多尺度分析

MULTI-SCALE ANALYSIS ON MOMENTUM FLUX OF TYPHOON CHANCHU DURING ITS LANDFALL

利用台风＂珍珠＂登陆前后的近地层湍流观测资料,分析了该台风经过观测场地前后地面气象要素的变化及其动量通量特征。结果表明,台风＂珍珠＂经过观测场地前后的近地层气象要素发生了急剧的变化,并且在台风前部存在强的中尺度对流系统,反映在风速能谱密度结构上,频率f在3×10^-4-2×10^-3Hz之间的中尺度信号对能谱的贡献比平稳天气形势下的能谱贡献大很多,尤其是顺风方向风速的能谱密度的峰值与湍流信号的峰值相当;动量通量分析结果表明,台风中心经过观测场地的前后三小时,近地层通量以向下输送的中尺度通量为主,湍流通量的贡献相对于中尺度通量较小,也是向下输送的;而在其他时段,近地层通量主要以向上输送的湍流通量为主,中尺度通量量值很小,可以忽略。

Near-surface turbulence data observed around the landfall of Typhoon Chanchu were used to analyze the variation of meteorological elements and momentum fluxes in this paper. Results showed that as Chanchu was passing an observation field after landfall, temperature, wind speed and direction, vertical velocity and pressure changed greatly. Besides there was a mesoscale system of strong convection in the front of the typhoon. Analysis of the velocity spectral density showed that mesoscale eddies with frequency ranging from 3~10-4 Hz to 2x10 3 Hz contributed more energy than those in stationary weather systems. Especially, longitudinal velocity spectra have a peak （1.5） in this range, which almost reached the peak value of the turbulence range. The momentum flux analysis showed that the mesoscale flux was negative and played a more important role than positive turbulence flux from 00：00 to 03：00 on June 18th. During other time, however, the positive turbulence flux played a more important role, and mesoscale flux was negligible though it was still negative.