A first-order closure scheme to describe counter-gradient momentum transport in plant canopies

✍ Scribed by Z. J. Li; D. R. Miller; J. D. Lin

• Publisher: Springer
• Year: 1985
• Tongue: English
• Weight: 330 KB
• Volume: 33
• Category: Article
• ISSN: 0006-8314
• DOI: 10.1007/bf00137037

✦ Synopsis

The gradient diffusion parameterization of the Reynolds stress is modified by adding a bulk momentum transport term. Comparisons to available data indicate that this term accounts for the gusts or 'downsweeps' of higher momentum fluid into the canopy and ejections of lower momentum fluid out of the canopy. This term results in realistic mean wind speed profiles. A A max 4 Cd d Fd h h max K k I t 4 0, w !!!L-11) w; u* x, Y, z zo ; P v -<> n List of Symbols leaf surface area density (m2 m -3, the maximum of A (m' m -3, reference value of A (m' m -3, drag coefficient (0.165) zero plane displacement (m) drag force per unit mass (m sm2) height of the canopy (m) the height of A,,, (m) diffusivity coefficient (m2 s -') von Karman constant (0.4) mixing length (m) time (s) wind speed components (m s -') reference velocity at a level above the canopy top (m s -') Reynolds stress at the canopy top (m s -',' friction velocity (m s-') coordinates (m) roughness length (m) constant (0.04) (s-l) constant (0.8) (m) air density (g cm -3, Laplacian operator time average spatial average fluctuation with time fluctuation with space