calc_daily_evap {splash}

Calculate daily evaporation fluxes

Description

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

Usage

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"))
cat(sprintf("  s: %0.6f Pa/K\n", evap$s_pa.k))
cat(sprintf("  Lv: %0.6f MJ/kg\n", (1e-6) * evap$lv_j.kg))
cat(sprintf("  Patm: %0.6f bar\n", (1e-5) * evap$patm_pa))
cat(sprintf("  pw: %0.6f kg/m^3\n", evap$pw_kg.m3))
cat(sprintf("  gamma: %0.6f Pa/K\n", evap$gam_pa.k))
cat(sprintf("  Econ: %0.6f mm^3/J\n", (1e9) * evap$econ_m3.j))
cat(sprintf("  Cn: %0.6f mm\n", evap$cond_mm))
cat(sprintf("  rx: %0.6f\n", evap$rx))
cat(sprintf("  hi: %0.6f degrees\n", evap$hi_deg))
cat(sprintf("  EET: %0.6f mm\n", evap$eet_mm))
cat(sprintf("  PET: %0.6f mm\n", evap$pet_mm))
cat(sprintf("  AET: %0.6f mm\n", evap$aet_mm))