Learn R Programming

Evapotranspiration (version 1.7)

constants: Constants Required for Calculating Evapotranspriation

Description

This data set contains the constants required for calculating evapotranspiration in function ET for Kent Town station in Adelaide, Australia.

Usage

climatedata

Arguments

format

A list containing 46 constant values including: "lambda", latent heat of evaporisationin = 2.45 MJ.kg^-1 at 20 degree Celcius, "sigma", Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1. "Gsc", solar constant = 0.0820 MJ.m^-2.min^-1, "lat", latitude = -34.9211 degrees for Kent Town station, "lat_rad", latitude in radians = -0.6095 radians for Kent Town station, "as", fraction of extraterrestrial radiation reaching earth on sunless days = 0.23 for Australia (Roderick, 1999, page 181), "bs", difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days = =0.5 for Australia (Roderick, 1999, page 181), "Elev", ground elevation above mean sea level = 48m for Kent Town station, "z", height of wind instrument = 10m for Kent Town station, "Roua", mean density of air = 1.2 kg.m^-3 at 20 degree Celcius, "Ca", specific heat of air = 0.001013 MJ.kg^-1.K^-1, "G", soil heat flux negligible for daily time-step = 0 (Allen et al., 1998, page 68), "alphaA", Albedo for Class-A pan = 0.14, "alphaPT", Priestley-Taylor coefficient = 1.26 for Priestley-Taylor formula (Priestley and Taylor, 1972, Sect. 6; Eichinger et al., 1996, p.163); = 1.31 for Szilagyi-Jozsa formula (Szilagyi and Jozsa, 2008); = 1.28 for Brutsaert-Strickler formula (Brutsaert and Strickler, 1979), "ap", constant in Penpan formula = 2.4, "fz", constant in Morton's procedure = 28.0 W.m^-2.mbar^-1 for CRAE model for T >= 0 degree Celcius, = 28.0*1.15 W.m^-2.mbar^-1 for CRAE model for T < 0 degree Celcius; = 25.0 W.m^-2.mbar^-1 for CRWE model for T >= 0 degree Celcius, = 28.75 W.m^-2.mbar^-1 for CRWE model for T < 0 degree Celcius (Morton, 1983a, page65), "b0", constant in Morton's procedure = 1 (Chiew and McMahon, 1991, Table A1), "b1", constant in Morton's procedure = 14 W.m^-2 (Chiew and McMahon, 1991, Table A1), "b2", constant in Morton's procedure = 1.2 (Chiew and McMahon, 1991, Table A1), "a_0", constant for estimating sunshine hours from cloud cover data = 11.9 for Adelaide (Chiew and McMahon, 1991, Table A1), "b_0", constant for estimating sunshine hours from cloud cover data = -0.15 for Adelaide, "c_0", constant for estimating sunshine hours from cloud cover data = -0.25 for Adelaide, "d_0", constant for estimating sunshine hours from cloud cover data = -0.0107 for Adelaide "e0", constant for Blaney-Criddle formula = 0.81917 (Frevert et al., 1983, Table 1), "e1", constant for Blaney-Criddle formula = -0.0040922 (Frevert et al., 1983, Table 1), "e2", constant for Blaney-Criddle formula = 1.0705 (Frevert et al., 1983, Table 1), "e3", constant for Blaney-Criddle formula = 0.065649 (Frevert et al., 1983, Table 1), "e4", constant for Blaney-Criddle formula = -0.0059864 (Frevert et al., 1983, Table 1), "e5", constant for Blaney-Criddle formula = -0.0005967 (Frevert et al., 1983, Table 1), "gammaps", product of Psychrometric constant and atmospheric pressure as sea level = 0.66 mbar. degree Celcius^-1 for CRAE model for T >= 0 degree Celcius, = 0.66/1.15 mbar. degree Celcius^-1 for CRAE model for T < 0 degree Celcius, "epsilonMo", Land surface emissivity in Morton's procedure = 0.92, "PA", annual precipitation = 285.8mm for Kent Town station, "alphaMo", constant in Morton's procedure = 17.27 when T >= 0 degree Celcius, = 21.88 when T < 0 degree Celcius, "betaMo", constant in Morton's procedure = 237.3 degree Celcius when T >= 0 degree Celcius, = 265.5 degree Celcius when T < 0 degree Celcius, "sigmaMo", Stefan-Boltzmann constant in Morton's procedure = 5.67e-08 W.m^-2.K^-4, "lambdaMo", latent heat of vaporisation in Morton's procedure = 28.5W.day.kg^-1 when T >= 0 degree Celcius, = 28.5*1.15W.day.kg^-1 when T < 0 degree Celcius.

source

various references