G_soilcan: Canopy to soil aerodynamic conductance

In VEZY/DynACof: A Process-Based Model to Study Growth, Yield and Ecosystem Services of Coffee Agroforestry Systems

Description

Compute the aerodynamic conductance for sensible and latent heat between the center of the lowest canopy layer and the soil surface following Van de Griend and Van Boxel (1989).

Usage

G_soilcan(
  Wind,
  ZHT,
  Z_top,
  Z0 = Z_top * 0.1,
  ZPD = Z_top * 0.75,
  alpha = 1.5,
  ZW = ZPD + alpha * (Z_top - ZPD),
  LAI,
  extwind = 0,
  vonkarman = Constants()$vonkarman
)

Arguments

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: 0.1*Z_top
ZPD	Zero-plane displacement (m), Default: 0.75*Z_top
alpha	Constant for diffusivity at top canopy. Default: 1.5 following Van de Griend et al (1989).
ZW	Top height of the roughness sublayer (m). Default: ZPD+alpha*(Z_top-ZPD)
LAI	Total leaf area index above the soil (m2 leaf m-2 soil).
extwind	Extinction coefficient. Default: 0, no extinction.
vonkarman	Von Karman constant, default to Constants()$vonkarman, 0.41.

Details

alpha can also be computed as:

alpha= (zw-d)/(Z_top-d)

The aerodynamic conductance between the lowest canopy layer and the soil is computed as:

g_a0= 1/((Uh/Kh)*log(U_mid/U_0))

where U_mid is the wind speed at median cumulated LAI between the top and the soil, and U_0 the wind speed at soil surface.

Value

g_a0	The aerodynamic conductance of the air between the lowest canopy layer and the soil surface (m s-1)

References

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.

See Also

G_bulk() and GetWind(), which is used internaly.

Examples

# G_a0 for a coffee plantation managed in agroforestry system:
G_soilcan(Wind= 1, ZHT= 25, Z_top= 24,LAI= 4.5, extwind= 0.58)

VEZY/DynACof documentation built on Feb. 3, 2021, 8:52 p.m.