psychrometric_constant: Psychrometric constant

In WDNR-Water-Use/CSLSevap: Evapo(transpi)ration Calculations

Description

Calculates the psychrometric constant for a given elevation based on Equation 7 and 8 in Allen et al. (1998).

Usage

psychrometric_constant(
  z,
  atmp = NULL,
  lambda = 2.45,
  cp = 0.001013,
  epsilon = 0.622
)

Arguments

z	elevation above sea level (m)
atmp	air temperature (degrees C). Optional value used to calculate the latent heat of vaporization. Defaults to NULL to use constant value of lambda.
lambda	latent heat of vaporization (MJ/kg). Default is 2.45.
cp	specific heat at constant pressure (MJ/kg/degC). Default is 1.1013e-3.
epsilon	ratio molecular weight of water vapour/dry air (-). Default is 0.622

Value

gamma

the psychrometric constant for the given elevation (kPa/degrees C)

References

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration: Guidelines for computing crop water requirements. Rome: FAO. Retrieved from http://www.fao.org/docrep/X0490E/x0490e00.htm.

WDNR-Water-Use/CSLSevap documentation built on April 9, 2021, 1:35 a.m.