【摘要】 本文使用小波变换方法研究了下垫面对近地面层湍流特征的影响.研究表明,各向同性系数(ISO)可以很好的描述近地面层湍流各向同性特征的日变化,其中,ISO0.7等值线可以作为一条代表性曲线来直观刻画湍流各向同性的尺度范围.在对不同风向及风向转变过程中ISO0.7等值线的变化特征进行研究后发现,ISO0.7尺度范围主要受源区下垫面特征的影响:当风从陆面吹来时,ISO0.7尺度较小;从水面吹来时ISO0.7尺度较大;而从水陆混合下垫面吹来时ISO0.7尺度介于陆地和水面之间;当风向在水面风和陆面风不断转变并达到均衡时的情况与水陆混合下垫面的情况较为接近;当风向持续从一种新下垫面吹向原下垫面时,ISO0.7将逐渐从原下垫面对应的尺度范围过渡新下垫面的尺度范围.更多还原

【Abstract】 In this paper,the wavelet transform method is applied to the 35 m tower measured data to study the influence of underlying surface on turbulent characteristics of atmospheric surface layer.The result shows the isotropy coefficient(ISO) could illustrate the daytime variety of the isotropy of real atmosphere at different scales well,and the isoline of 0.7(ISO0.7) has a good typification to estimate the scale range of isotropy turbulence.The scale range of ISO0.7 is mainly under the influence of the characteristic of windward underlying surface.When winds blow from the land surface,the scale of ISO0.7is is smaller than that when from the lake;and when from the lake to land,ISO0.7is at a scale between that from the land and from the lake,near to that under the condition when the wind directions continuously vary between from the land and from the lake in equipoise.While winds blow from a new underlying to an old underlying constantly,the scales of ISO0.7will change gradually from scale range corresponding to the old underlying surface to that corresponding to the new underlying surface.更多还原