Calculate daily evaporation fluxes

Source: R/evap.R

This function calculates daily radiation, condensation, and evaporation fluxes.

calc_daily_evap(
  lat,
  n,
  elv = 0,
  y = 0,
  sf = 1,
  tc = 23,
  sw = 1,
  ke = 0.0167,
  keps = 23.44,
  komega = 283,
  kw = 0.26
)

Arguments

lat

double, decimal degrees.

n

double, day of year.

elv

double, elevation, m A.S.L. Default: \(0\).

y

double, year. Default: \(0\).

sf

double, fraction of sunshine hours. Default: \(1\).

tc

double, mean daily air temperature, degrees C. Default: \(23.0\).

sw

double, evaporative supply rate, mm/hr. Default: \(1.0\).

ke

double, eccentricity of earth's orbit. Default: \(0.01670\), 2000CE (Berger, 1978).

keps

double, obliquity of earth's elliptic. Default: \(23.44\), 2000CE (Berger, 1978).

komega

double, lon. of perihelion, degrees Default: \(283\), 2000CE (Berger, 1978).

kw

double, PET entrainment, \((1 + kw) * EET\) Default: \(0.26\) (Priestley-Taylor, 1972)

Value

Returns a list object with the following variables:

  • nu_deg ............ true anomaly, degrees

  • lambda_deg ........ true longitude, degrees

  • dr ................ distance factor, unitless

  • delta_deg ......... declination angle, degrees

  • hs_deg ............ sunset angle, degrees

  • ra_j.m2 ........... daily extraterrestrial radiation, J/m^2

  • tau ............... atmospheric transmittivity, unitless

  • ppfd_mol.m2 ....... daily photosyn photon flux density, mol/m^2

  • hn_deg ............ net radiation hour angle, degrees

  • rn_j.m2 ........... daily net radiation, J/m^2

  • rnn_j.m2 .......... daily nighttime net radiation, J/m^2

  • econ_m3.j ......... water to energy conversion, m^3/J

  • cond_mm ........... daily condensation, mm

  • eet_mm ............ daily equilibrium evapotranspiration, mm

  • pet_mm ............ daily potential evapotranspiration, mm

  • hi_deg ............ intersection hour angle, degrees

  • aet_mm ............ daily actual evapotranspiration, mm

References

Berger, A.L., 1978. Long-term variations of daily insolation and Quaternary climatic changes. Journal of Atmospheric Sciences, 35(12), pp.2362-2367. doi:10.1175/1520-0469(1978)035<2362:LTVODI>2.0.CO;2

Priestley, C.H.B. and Taylor, R.J., 1972. On the assessment of surface heat flux and evaporation using large-scale parameters. Monthly weather review, 100(2), pp.81-92. doi:10.1175/1520-0493(1972)100<0081:OTAOSH>2.3.CO;2

Examples

evap <- splash::calc_daily_evap(lat = 37.7,
                                n = 172,
                                elv = 142,
                                y = 2000,
                                sf = 1,
                                tc = 23.0,
                                sw = 0.9)
cat(sprintf("Evaporation values:\n"))
#> Evaporation values:
cat(sprintf("  s: %0.6f Pa/K\n", evap$s_pa.k))
#>   s: 169.896093 Pa/K
cat(sprintf("  Lv: %0.6f MJ/kg\n", (1e-6) * evap$lv_j.kg))
#>   Lv: 2.446687 MJ/kg
cat(sprintf("  Patm: %0.6f bar\n", (1e-5) * evap$patm_pa))
#>   Patm: 0.996308 bar
cat(sprintf("  pw: %0.6f kg/m^3\n", evap$pw_kg.m3))
#>   pw: 997.583620 kg/m^3
cat(sprintf("  gamma: %0.6f Pa/K\n", evap$gam_pa.k))
#>   gamma: 66.729719 Pa/K
cat(sprintf("  Econ: %0.6f mm^3/J\n", (1e9) * evap$econ_m3.j))
#>   Econ: 0.294167 mm^3/J
cat(sprintf("  Cn: %0.6f mm\n", evap$cond_mm))
#>   Cn: 0.885192 mm
cat(sprintf("  rx: %0.6f\n", evap$rx))
#>   rx: 0.001334
cat(sprintf("  hi: %0.6f degrees\n", evap$hi_deg))
#>   hi: 20.959320 degrees
cat(sprintf("  EET: %0.6f mm\n", evap$eet_mm))
#>   EET: 6.405468 mm
cat(sprintf("  PET: %0.6f mm\n", evap$pet_mm))
#>   PET: 8.070889 mm
cat(sprintf("  AET: %0.6f mm\n", evap$aet_mm))
#>   AET: 7.972788 mm