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Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height no longer follows a mathematical logarithm. It is so named because it is typically related to the height of terrain roughness elements (i.e. protrusions from and/or depressions into the surface). For instance, forests tend to have much larger roughness lengths than tundra. The roughness length does not exactly correspond to any physical length. However, it can be considered as a length-scale representation of the roughness of the surface.

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  • Longueur de rugosité (fr)
  • 粗度係数 (ja)
  • Roughness length (en)
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  • Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height no longer follows a mathematical logarithm. It is so named because it is typically related to the height of terrain roughness elements (i.e. protrusions from and/or depressions into the surface). For instance, forests tend to have much larger roughness lengths than tundra. The roughness length does not exactly correspond to any physical length. However, it can be considered as a length-scale representation of the roughness of the surface. (en)
  • 粗度係数(そどけいすう)とは、河川の水が河床や河岸などと触れる際の抵抗量を示した数値。人工水路よりも起伏、曲線、障害物(水草、礫等)に富んだ自然河川の方が値は高くなる。 (ja)
  • La longueur de rugosité efficace (z0) est un paramètre de longueur caractéristique relié à l'effet de la rugosité de surface dans un flux complètement turbulent. Dans le modèle du profil logarithmique des vitesses de la couche limite, ce paramètre est équivalent à la hauteur à laquelle la vitesse théorique du vent deviendrait nulle Sous cette hauteur, la vitesse du vent ne suit plus une loi logarithmique. (fr)
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  • Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height no longer follows a mathematical logarithm. It is so named because it is typically related to the height of terrain roughness elements (i.e. protrusions from and/or depressions into the surface). For instance, forests tend to have much larger roughness lengths than tundra. The roughness length does not exactly correspond to any physical length. However, it can be considered as a length-scale representation of the roughness of the surface. (en)
  • La longueur de rugosité efficace (z0) est un paramètre de longueur caractéristique relié à l'effet de la rugosité de surface dans un flux complètement turbulent. Dans le modèle du profil logarithmique des vitesses de la couche limite, ce paramètre est équivalent à la hauteur à laquelle la vitesse théorique du vent deviendrait nulle Sous cette hauteur, la vitesse du vent ne suit plus une loi logarithmique. Bien que n'étant pas en soi une quantité physique, cette longueur peut être considérée comme une échelle de longueur représentant la rugosité de la surface reliée à la hauteur des obstacles dans une zone donnée. La longueur de rugosité est un concept important en météorologie urbaine en ce sens que les constructions de grande hauteur comme les gratte-ciels ont une influence importante sur la répartition des vents et la longueur de rugosité. (fr)
  • 粗度係数(そどけいすう)とは、河川の水が河床や河岸などと触れる際の抵抗量を示した数値。人工水路よりも起伏、曲線、障害物(水草、礫等)に富んだ自然河川の方が値は高くなる。 (ja)
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