Description Usage Arguments Details Value References See Also Examples
Compute the aerodynamic conductance for sensible and latent heat between canopy layers following Van de Griend and Van Boxel (1989).
1 2 3 4 5 6 7 8 9 10 11 12 13 | G_interlay(
Wind,
ZHT,
Z_top,
Z0 = Z_top * 0.1,
ZPD = Z_top * 0.75,
alpha = 1.5,
ZW = ZPD + alpha * (Z_top - ZPD),
LAI_top,
LAI_bot,
extwind = 0,
vonkarman = Constants()$vonkarman
)
|
Wind |
Average daily wind speed above canopy (m s-1) |
ZHT |
Wind measurement height (m) |
Z_top |
Average canopy height of the taller crop (m) |
Z0 |
Roughness length (m). Default: |
ZPD |
Zero-plane displacement (m), Default: |
alpha |
Constant for diffusivity at top canopy. Default: |
ZW |
Top height of the roughness sublayer (m). Default: |
LAI_top |
Leaf area index of the upper layer (m2 leaf m-2 soil). |
LAI_bot |
Leaf area index of the layer below the upper layer (m2 leaf m-2 soil). |
extwind |
Extinction coefficient. Default: |
vonkarman |
Von Karman constant, default to |
alpha
can also be computed as:
alpha= (zw-d)/(Z_top-d)
The aerodynamic conductance between canopy layers is computed as:
g_af= 1/((Uh/Kh)*log(U_mid/U_inter))
where usually U_mid is the wind speed at (median) cumulated LAI between the top and the soil, and U_inter the wind speed at the height between the two canopy layers. In this function, U_mid and U_inter are computed relative to the leaf area instead of the height of the vegetation layers.
g_af |
The aerodynamic conductance of the air between two canopy layers (m s-1) |
Van de Griend, A.A. and J.H. Van Boxel, Water and surface energy balance model with a multilayer canopy representation for remote sensing purposes. Water Resources Research, 1989. 25(5): p. 949-971.
G_bulk()
and GetWind()
, which is used internaly.
1 2 | # G_af for a coffee plantation managed in agroforestry system:
G_interlay(Wind = 3,ZHT = 25,Z_top = 2,LAI_top = 0.5,LAI_bot = 4)
|
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