An empirical formulation for the canopy boundary layer conductance for heat transfer based on a simple ustar dependency.
Gb.Thom(ustar, Sc = NULL, Sc_name = NULL, constants = bigleaf.constants())a data.frame with the following columns:
Boundary layer conductance for heat transfer (m s-1)
Boundary layer resistance for heat transfer (s m-1)
kB-1 parameter for heat transfer
Boundary layer conductance for Sc_name (m s-1). Only added if Sc_name and
Sc_name are provided
Friction velocity (m s-1)
Optional: Schmidt number of additional quantities to be calculated
Optional: Name of the additional quantities, has to be of same length than
Sc_name
k - von-Karman constant
Sc_CO2 - Schmidt number for CO2
Pr - Prandtl number (if Sc is provided)
The empirical equation for Rb suggested by Thom 1972 is:
$$Rb = 6.2ustar^-0.67$$
Gb (=1/Rb) for water vapor and heat are assumed to be equal in this package. Gb for other quantities x is calculated as (Hicks et al. 1987):
$$Gb_x = Gb / (Sc_x / Pr)^0.67$$
where Sc_x is the Schmidt number of quantity x, and Pr is the Prandtl number (0.71).
Thom, A., 1972: Momentum, mass and heat exchange of vegetation. Quarterly Journal of the Royal Meteorological Society 98, 124-134.
Hicks, B.B., Baldocchi, D.D., Meyers, T.P., Hosker, J.R., Matt, D.R., 1987: A preliminary multiple resistance routine for deriving dry deposition velocities from measured quantities. Water, Air, and Soil Pollution 36, 311-330.
Gb.Choudhury, Gb.Su, aerodynamic.conductance
Gb.Thom(seq(0.1,1.4,0.1))
## calculate Gb for SO2 as well
Gb.Thom(seq(0.1,1.4,0.1),Sc=1.25,Sc_name="SO2")
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