ET0_models: Potential Evapotranspiration models

In rpkgs/hydroTools: Tools for hydrological model

Potential Evapotranspiration models

Description

• ET0_eq : Equilibrium evaporation, slope / (slope + gamma) * Rn

• ET0_Penman48 : Penman 1948 equation simplified by Shuttleworth 1993

• ET0_Monteith65: Penman-Monteith 1965

• ET0_PT72 : Priestley Taylor 1972, ET0_PT72 = ET0_eq * 1.26

• ET0_FAO98 : Penman-Monteith reference crop evapotranspiration, FAO56

Usage

ET0_eq(Rn, Tair, Pa = atm, ...)

ET0_Penman48(Rn, Tair, Pa = atm, D, wind, z.wind = 2)

ET0_Monteith65(
  Rn,
  Tair,
  Pa = atm,
  D,
  wind,
  z.wind = 2,
  rs = 70,
  rH = NULL,
  ...
)

ET0_PT72(Rn, Tair, Pa = atm, alpha = 1.26, ...)

ET0_FAO98(Rn, Tair, Pa = atm, D, wind, z.wind = 2, tall_crop = FALSE)

Arguments

Rn	land surface net radiation, W m-2
Tair	2m air temperature (degC)
Pa	surface air pressure (kPa)
D	vapor pressure deficit (kPa)
wind	wind speed at the height of z.wind
z.wind	Height where measure the wind speed ⁠[m]⁠. Default 2m.
alpha	albedo ⁠[0-1]⁠
tall_crop	tall crop or not, see FAO1998 for details

Value

• lambda: Latent heat of vaporization, about ⁠[2.5 MJ kg-1]⁠.

• slope : The slope of the saturation vapour pressure curve at certain air temperature Tair, ⁠[kPa degC-1]⁠.

• gamma : Psychrometric constant (⁠[kPa degC-1]⁠), Cp*Pa/(epsilon*lambda)

• Eeq : Equilibrium (radiative) evaporation, mm

• Evp : Aerodynamic evaporation, mm

• ET0 : Potential evapotranspiration, mm

References

1. Penman equation. Wikipedia 2021. https://en.wikipedia.org/w/index.php?title=Penman_equation

2. Shuttleworth, W. J. (1993) Evaporation. In: Handbook of Hydrology (ed. by D. Maidment). McGraw-Hill, New York.

3. Allen, R. G., & Luis S. Pereira. (1998). Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. European Journal of Agronomy, 34(3), 144-152. doi:10.1016/j.eja.2010.12.001

4. Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). FAO Irrigation and drainage paper No. 56. Rome: Food and Agriculture Organization of the United Nations, 56(97), e156.

5. Chapter 2 - FAO Penman-Monteith equation, https://www.fao.org/3/x0490E/x0490e06.htm

Examples

ET0_PT72(250, 25, D = 1)
ET0_Penman48(250, 25, D = 1, wind = 2)
ET0_FAO98(250, 25, D = 1, wind = 2)
ET0_Monteith65(250, 25, D = 1, wind = 2)

rpkgs/hydroTools documentation built on Oct. 8, 2024, 7:47 p.m.