Constants used in the DynACof package

Constants()

Value

This function defines the following constants:

specific heat of air for constant pressure (\(J\ K^{-1}\ kg^{-1}\)), Source: Allen 1998 FAO Eq. 8 p. 32

pressure0

reference atmospheric pressure at sea level (\(Pa\))

FPAR

Fraction of global radiation that is PAR (source: MAESPA model)

gravitational acceleration (\(m\ s^{-2}\))

gas constant of dry air (\(J\ kg^{-1}\ K^{-1}\)), source : Foken p. 245

Rgas

universal gas constant (\(J\ mol^{-1}\ K^{-1}\))

Kelvin

conversion degree Celsius to Kelvin

vonkarman

von Karman constant (-)

MJ_to_W

coefficient to convert MJ into W (\(W\ MJ^{-1}\))

Gsc

solar constant (\(W\ m^{-2}=J\ m^{-2}\ s^{-1}\), ), source : Khorasanizadeh and Mohammadi (2016)

sigma

Stefan-Boltzmann constant (\(W\ m^{-2}\ K^{-4}\))

H2OMW

Conversion factor from kg to mol for H2O (\(kg\ mol^{-1}\))

W_umol

Conversion factor from watt to micromole for H2O (\(W\ \mu mol^{-1}\))

\(\lambda\)(lambda)

Latent heat of vaporization (\(MJ\ kg_{H2O}^{-1}\))

Drag coefficient per unit leaf area (\(m\ s^{-1}\))

Dheat

Molecular diffusivity for heat (\(m\ s^{-1}\))

GBVGBH

Conversion factor from conductance to water to conductance to heat.

M_H20

H2O molar mass (\(kg\\ mol^{-1}\))

Values are partly burrowed from bigleaf::bigleaf.constants()

Allen, R. G., et al. (1998). "Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56." 300(9): D05109.
Foken, T, 2008: Micrometeorology. Springer, Berlin, Germany.
Khorasanizadeh, H. and K. Mohammadi (2016). "Diffuse solar radiation on a horizontal surface: Reviewing and categorizing the empirical models." Renewable and Sustainable Energy Reviews 53: 338-362.