WIND STRUCTURE IN STRONG WINDS BELOW 150 M
WIND STRUCTURE IN STRONG WINDS BELOW 150 M
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作者：
H. Panofsky
在讨论风的脉动时，提出150米以下的风的结构在很大程度上取决于大尺度气压梯度和湍流特性。大气湍流的两种主要形式被描述为机械湍流，由垂直切变和风驱动;和热对流，通常由下面的加热驱动。作者认为，在强风中，机械湍流往往远强于热对流，而后者可以忽略不计。因此，这一主题的回顾关注的是占主导地位的机械湍流条件下的风的特性，但是否可以忽略热对流的问题也讨论了参考理查森数。综述讨论了强风时均匀地形上的平均风分布;参照莫宁-奥布霍夫理论，稳定性对风廓线的影响;地形变化对风速的影响，即当空气从粗糙地形移向光滑地形时，表面应力立即下降，使地面上方的空气加速;风的变率;用共谱和正交谱描述风速的互谱或由它们导出的统计量。/TRRL/
In a discussion of wind fluctuations it is suggested that the structure of winds below 150 M is largely determined by the large-scale pressure gradient and the characteristics of turbulence. Two main forms of atmospheric turbulence are described as mechanical turbulence, driven by the vertical shear and the wind; and heat convection, generally driven by heating from below. The author considers that in strong winds, mechanical turbulence is frequently far stronger than heat convection, and that the latter can be neglected. This review of the subject is therefore concerned with wind properties under conditions of dominant mechanical turbulence, but the question of whether or not heat convection can be neglected is also discussed by reference to the richardson number. The review discusses the distribution of mean wind over homogeneous terrain in strong winds; the effect of stability on wind profiles by reference to the monin-obukhov theory; the effect of terrain change on wind speed, in that when air moves from rough to smooth terrain the surface stress immediately drops so that just above the ground the air accelerates; wind variability; and cross spectra of wind speed as described by cospectrum and quadrature spectrum or statistics derived from them. /TRRL/