Title: | Evapotranspiration Based on FAO Penman-Monteith Equation |
---|---|
Description: | Calculation of Evapotranspiration by FAO Penman-Monteith equation based on Allen, R. G., Pereira, L. S., Raes, D., Smith, M. (1998, ISBN:92-5-104219-5) "Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56". |
Authors: | Ali Ahani [aut, cre] <[email protected]> , S. Saeid Mousavi Nadoushani [aut] <[email protected]> |
Maintainer: | Ali Ahani <[email protected]> |
License: | GPL (>= 2) |
Version: | 1.0 |
Built: | 2024-11-09 03:06:16 UTC |
Source: | https://github.com/cran/FAO56 |
FAO56 provides the equations used to calulate the crop evapotranspiration and evapotranspiration rate from the reference surface by FAO Penman-Monteith equation based on FAO paper No, 56: Crop evapotranspiration - Guidelines for computing crop water requirements
AtmPres
returns the value of atmospheric pressure.
AtmPres(z)
AtmPres(z)
z |
A numeric scalar that denotes elevation above sea level [m]. |
This is a function to calculate the atmospheric pressure [kPa] based on the elevation above the sea level.
The function returns the value of the atmospheric pressure as a numeric scalar.
AtmPres(z = 1800)
AtmPres(z = 1800)
CSSRad
returns the value of clear-sky solar radiation.
CSSRad(a_s = 0.25, b_s = 0.5, elev = NULL, R_a)
CSSRad(a_s = 0.25, b_s = 0.5, elev = NULL, R_a)
a_s |
Optional. A numeric scalar that denotes regression constant, expressing the fraction ofextraterrestrial radiation
reaching the earth on overcast days (n = 0). The default is |
b_s |
Optional. A numeric scalar that denotes fraction of extraterrestrial radiation reaching the earth on clear days
( |
elev |
Optional. A numeric scalar that denotes the elevation above the sea level [m]. |
R_a |
A numeric scalar that denotes extraterrestrial radiation [ |
This is a function to calculate the clear-sky solar radiation. The argument elev
is needed when the calibrated values
of a_s
and b_s
are not available.
The function returns the value of clear-sky solar radiation as a numeric scalar.
CSSRad(a_s = 0.27, b_s = 0.48, R_a = 25.1) CSSRad(elev = 100, R_a = 25.1)
CSSRad(a_s = 0.27, b_s = 0.48, R_a = 25.1) CSSRad(elev = 100, R_a = 25.1)
DD2Rad
converts the value of an angel in the unit degree to the unit radian.
DD2Rad(phi_deg)
DD2Rad(phi_deg)
phi_deg |
Optional. A numeric scalar that denotes the latitude in terms of degree [degree]. |
This is a function to convert the degree unit to radian.
The function convert the value of an angel in the unit degree to the unit radian as a numeric scalar.
DD2Rad(phi_deg = 60.73)
DD2Rad(phi_deg = 60.73)
DH
returns the value of daylight hours.
DH(omega_s)
DH(omega_s)
omega_s |
A numeric scalar that denotes the sunset hour angle [rad]. |
This is a function to calculate the daylight hours.
The function returns the value of daylight hours as a numeric scalar.
DH(omega_s = 1.527)
DH(omega_s = 1.527)
EarSunDis
returns the inverse earth-sun distance.
EarSunDis(date)
EarSunDis(date)
date |
Optional. A character string that denotes the date in the format "Year-Month-Day" or "Year/Month/Day". |
This is a function to calculate the inverse earth-sun distance.
The function returns the value of inverse relative earth-sun distance as a numeric scalar.
EarSunDis("2020/08/25")
EarSunDis("2020/08/25")
EffPrec
returns the value of effective precipitation.
EffPrec(P_tot)
EffPrec(P_tot)
P_tot |
A numeric scalar that denotes the total monthly precipitation [mm]. |
This is a function to calculate the effective precipitation [mm]. The function formula has been developed for Iran where the mean annual precipitation is about 250 mm. It may be used for similar semi-arid areas, but it is not recommended for the areas with different climate.
The function returns the value of effective monthly precipitation [mm].
EffPrec(P_tot = 450)
EffPrec(P_tot = 450)
ET_c
returns the value of crop evapotranspiration.
ET_c(Kc, ETo)
ET_c(Kc, ETo)
Kc |
A numeric scalar that denotes the crop coefficient (Kc). |
ETo |
A numeric scalar that denotes the evapotranspiration rate from the reference surface [mm]. |
This is a function to calculate the crop evapotranspiration.
The function returns the value of crop evapotranspiration as a numeric scalar.
# First example ET_c(Kc = 0.6, ETo = 0.9) # Second example # Computing ET_c of the crop millet planted in Sahiwal, Pakistan # for a specific day in the initial growth stage ## Loading the relevant Kc dataset data(Kc_Cereals) ## Latitude in decimal degree latdeg = 31.685 ## Date (2020 June 7) pdate = "2020-06-07" ## Maximum and minimum temperatures in celsius temp_max = 38 temp_min = 28 ## Actual duration of sunshine and maximum possible duration of sunshine or daylight in hours actsunshine = 13 maxdaylight = 14 ## Elevation above sea level in meter h = 170 ## Wind speed in the height 2m above the ground surface in m/s ws = 2 ## Evapotranspiration rate from the reference surface (ETo) in mm/day ET_ref = ETo_FPM(u_2 = ws, e_a = 2.85, T_min = temp_min, T_max = temp_max, phi_deg = latdeg, elev = h, date = pdate, n = actsunshine, N = maxdaylight) ## Crop ET CrET = ET_c(Kc = Kc_Cereals$Kc_ini[12], ETo = ET_ref)
# First example ET_c(Kc = 0.6, ETo = 0.9) # Second example # Computing ET_c of the crop millet planted in Sahiwal, Pakistan # for a specific day in the initial growth stage ## Loading the relevant Kc dataset data(Kc_Cereals) ## Latitude in decimal degree latdeg = 31.685 ## Date (2020 June 7) pdate = "2020-06-07" ## Maximum and minimum temperatures in celsius temp_max = 38 temp_min = 28 ## Actual duration of sunshine and maximum possible duration of sunshine or daylight in hours actsunshine = 13 maxdaylight = 14 ## Elevation above sea level in meter h = 170 ## Wind speed in the height 2m above the ground surface in m/s ws = 2 ## Evapotranspiration rate from the reference surface (ETo) in mm/day ET_ref = ETo_FPM(u_2 = ws, e_a = 2.85, T_min = temp_min, T_max = temp_max, phi_deg = latdeg, elev = h, date = pdate, n = actsunshine, N = maxdaylight) ## Crop ET CrET = ET_c(Kc = Kc_Cereals$Kc_ini[12], ETo = ET_ref)
ETo_FPM
returns the value of evapotranspiration rate from the reference surface.
ETo_FPM( Delta = SlpSVPC(T_mean), T_mean = (T_min + T_max)/2, R_n = NULL, G = 0, gamma = PsyCon(AtmPres(elev)), u_2 = NULL, u_z = NULL, z = NULL, e_s = MSVP(T_max, T_min), T_dew = NULL, e_a = NULL, T_min = NULL, T_max = NULL, phi_deg = NULL, elev = NULL, date = NULL, n = NULL, N = NULL, a_s = 0.25, b_s = 0.5 )
ETo_FPM( Delta = SlpSVPC(T_mean), T_mean = (T_min + T_max)/2, R_n = NULL, G = 0, gamma = PsyCon(AtmPres(elev)), u_2 = NULL, u_z = NULL, z = NULL, e_s = MSVP(T_max, T_min), T_dew = NULL, e_a = NULL, T_min = NULL, T_max = NULL, phi_deg = NULL, elev = NULL, date = NULL, n = NULL, N = NULL, a_s = 0.25, b_s = 0.5 )
Delta |
Optional. A numeric scalar that denotes the slope vapour pressure curve [kPa/C]. |
T_mean |
Optional. A numeric scalar that denotes the average temperature [C]. |
R_n |
Optional. A numeric scalar that denotes the net radiation at the crop surface [ |
G |
Optional. A numeric scalar that denotes the soil heat flux density [ |
gamma |
Optional. A numeric scalar that denotes the psychrometric constant [kPa/C]. |
u_2 |
A numeric scalar that denotes the wind speed at the height 2m above the ground surface [m/s]. |
u_z |
A numeric scalar that denotes the wind speed at the height |
z |
A numeric scalar that denotes the height above the ground surface where the wind speed has been measured [m]. |
e_s |
Optional. A numeric scalar that denotes the saturation vapour pressure [kPa]. |
T_dew |
Optional. A numeric scalar that denotes the dew point temperature [C]. |
e_a |
Optional. A numeric scalar that denotes the actual vapour pressure [kPa]. |
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
phi_deg |
Optional. A numeric scalar that denotes the latitude in terms of degree [degree]. |
elev |
Optional. A numeric scalar that denotes the elevation above the sea level [m]. |
date |
Optional. A character string that denotes the date in the format "Year-Month-Day" or "Year/Month/Day". |
n |
Optional. A numeric scalar that denotes actual duration of sunshine [hour] |
N |
Optional. A numeric scalar that denotes maximum possible duration of sunshine or daylight hours [hour] |
a_s |
Optional. A numeric scalar that denotes regression constant, expressing the fraction ofextraterrestrial radiation
reaching the earth on overcast days (n = 0). The default is |
b_s |
Optional. A numeric scalar that denotes fraction of extraterrestrial radiation reaching the earth on clear days
( |
This is a function to calculate the evapotranspiration rate from the reference surface (ETo)
by using FAO Penman-Monteith equation which is one of the most-widely used equations
for this purpose. If Delta
is missing, the function uses the argumnet T_mean
to compute its value. If T_mean
is missing, the function needs T_min
and T_max
to compute T_mean
. If R_n
is missing, the arguments phi_deg
, date
,
n
, N
, elev
, T_min
, T_max
, and e_a
must be present.
If gamma
is missing, the function needs elev
to compute gamma
.
If e_s
is missing, the arguments T_min
and T_max
must be present for
computation of e_s
. If e_a
is missing, one of the arguments T_dew
or
T_min
must be present in order to compute e_a
. If T_dew
is missing and T_min
is present, then T_dew
is computed based on the T_min
value. If u_2
is missing,
the function needs the values of the arguments u_z
and z
to compute u_2
.
The function returns the value of evapotranspiration rate from the reference surface as a numeric scalar.
ETo_Hrg
for Hargreaves Equation.
ETo_FPM(u_2 = 2, e_a = 2.85, T_min = 25.6, T_max = 34.8, phi_deg = 13.73, elev = 2, date = '2002-04-15', n = 8.5, N = 12.31)
ETo_FPM(u_2 = 2, e_a = 2.85, T_min = 25.6, T_max = 34.8, phi_deg = 13.73, elev = 2, date = '2002-04-15', n = 8.5, N = 12.31)
ETo_Hrg
returns the value of the evapotranspiration rate from the reference surface.
ETo_Hrg(T_min, T_max, R_a)
ETo_Hrg(T_min, T_max, R_a)
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
R_a |
A numeric scalar denotes the extraterrestrial radiation [ |
This is a function to calculate the evapotranspiration rate from the reference surface (ETo) by using Hargreaves equation.
The function returns the value of evapotranspiration rate from the reference surface calculated by Hargreaves equation [mm/day] as a numeric scalar.
ETo_FPM
for FAO Penman-Monteith Equation.
ETo_Hrg(T_min = 19, T_max = 25, R_a = 32)
ETo_Hrg(T_min = 19, T_max = 25, R_a = 32)
ETo_Pan
returns the value of reference evapotranspiration based on the pan evaporation method.
ETo_Pan(K_p, E_pan)
ETo_Pan(K_p, E_pan)
K_p |
A numeric scalar that denotes the pan coefficient. |
E_pan |
A numeric scalar that denotes the pan evaporation [mm/day]. |
This is a function to calculate the reference evapotranspiration [mm/day] based on the pan evaporation method.
The function returns the value of the reference evapotranspiration as a numeric scalar.
ETo_Pan(K_p = 0.6, E_pan = 5)
ETo_Pan(K_p = 0.6, E_pan = 5)
ExRad
returns the value of extraterrestrial radiation [].
ExRad(d_r, omega_s, phi, delta, G_sc = 0.082)
ExRad(d_r, omega_s, phi, delta, G_sc = 0.082)
d_r |
A numeric scalar that denotes the inverse relative earth-sun distance. |
omega_s |
A numeric scalar that denotes the sunset hour angle [rad]. |
phi |
A numeric scalar that denotes the latitude [rad]. |
delta |
A numeric scalar that denotes the solar declination [rad]. |
G_sc |
A numeric scalar that denotes the solar constant = 0.0820 [ |
This is a function to calculate the extraterrestrial radiation.
The function returns the value of extraterrestrial radiation as a numeric scalar.
EarSunDis, SunHA, SolDec, SolRad, CSSRad
.
ExRad(d_r = 0.985, omega_s = 1.527, phi = -0.35, delta = 0.12)
ExRad(d_r = 0.985, omega_s = 1.527, phi = -0.35, delta = 0.12)
JulDate
returns Julian Date.
JulDate(date)
JulDate(date)
date |
Optional. A character string that denotes the date in the format "Year-Month-Day" or "Year/Month/Day". |
This is a function to calculate Julian Date.
The function returns Julian Date as a numeric scalar.
JulDate(date = "2020-06-25") JulDate(date = "2020/06/25")
JulDate(date = "2020-06-25") JulDate(date = "2020/06/25")
A dataset containing the crop coefficients (Kc) of the cereals extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 17 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the fibre crops extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 3 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the forages extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 15 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the fruit trees extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 21 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the grapes and berries extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 4 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the legumes extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 13 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the oil crops extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 8 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the perennial vegetables extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 4 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the roots and tubers extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 8 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the small vegetables extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 13 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the special areas extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 2 rows and 3 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the sugar cane extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 1 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the tropical fruits and trees extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 12 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the cucumber family vegetables extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 7 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the solanum family vegetables extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 4 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
A dataset containing the crop coefficients (Kc) of the wetlands temperate climate extracted from Table 12 in
"Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56".
It is a source to assign a suitable value to the argument Kc
of the function ET_c
.
A data frame with 5 rows and 4 variables:
name of the crop
the crop coefficient in the growth initial stage
the crop coefficient in the growth mid-season stage
the crop coefficient in the growth late-season stage
https://www.fao.org/3/x0490E/x0490e00.htm
MeanRH
returns the value of mean relative humidity.
MeanRH(T_min, T_max)
MeanRH(T_min, T_max)
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
This is a function to calculate the mean relative humidity.
The function returns the value of the mean relative humidity as a numeric scalar.
MeanRH(T_min = 19, T_max = 26)
MeanRH(T_min = 19, T_max = 26)
MeanTemp
returns the value of mean daily air temperature [C].
MeanTemp(T_min, T_max)
MeanTemp(T_min, T_max)
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
This is a function to calculate the mean daily air temperature [C].
The function returns the value of the mean daily air temperature [C] as a numeric scalar.
MeanTemp(T_min = 5, T_max = 35)
MeanTemp(T_min = 5, T_max = 35)
MSVP
returns the value of mean saturation vapour pressure.
MSVP(T_max, T_min)
MSVP(T_max, T_min)
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
This is a function to calculate the mean saturation vapour pressure [kPa].
The function returns the value of the mean saturation vapour pressure [kPa] as a numeric scalar.
MSVP(T_max = 35, T_min = 1)
MSVP(T_max = 35, T_min = 1)
NLRad
returns the value of net longwave radiation.
NLRad(T_max, T_min, e_a, R_s, R_so)
NLRad(T_max, T_min, e_a, R_s, R_so)
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
e_a |
Optional. A numeric scalar that denotes the actual vapour pressure [kPa]. |
R_s |
A numeric scalar that denotes the incoming solar radiation [ |
R_so |
A numeric scalar that denotes clear-sky radiation [ |
This is a function to calculate the net longwave radiation [].
The function returns the value of net solar or net shortwave radiation as a numeric scalar.
NLRad(T_max = 25.1, T_min = 19.1, e_a = 2.1, R_s = 14.5, R_so = 18.8)
NLRad(T_max = 25.1, T_min = 19.1, e_a = 2.1, R_s = 14.5, R_so = 18.8)
NRad
returns the value of net radiation.
NRad(R_ns, R_nl)
NRad(R_ns, R_nl)
R_ns |
A numeric scalar that denotes net shortwave radiation [ |
R_nl |
A numeric scalar that denotes net longwave radiation [ |
This is a function to calculate the net radiation [].
The function returns the value of net solar radiation as a numeric scalar.
NRad(R_ns = 11.1, R_nl = 3.5)
NRad(R_ns = 11.1, R_nl = 3.5)
NSRad
returns the value of net shortwave radiation.
NSRad(R_s)
NSRad(R_s)
R_s |
A numeric scalar that denotes the incoming solar radiation [ |
This is a function to calculate the net shortwave radiation.
The function returns the value of net shortwave radiation as a numeric scalar.
NSRad(R_s = 14.5)
NSRad(R_s = 14.5)
PanCoef
returns the value of Pan Coefficient (K_p).
PanCoef(u_2, RH_mean, FET, type, fetch)
PanCoef(u_2, RH_mean, FET, type, fetch)
u_2 |
A numeric scalar that denotes the wind speed at the height 2m above the ground surface [m/s]. |
RH_mean |
A numeric scalar that denotes the mean relative humidity. ( |
FET |
A numeric scalar that denotes the fetch, or distance of the identified surface type [m] ( |
type |
A character string that denotes the type of pan and can take the options "Class A" for Class A pan and "Colorado" for Colorado sunken pan. |
fetch |
A character string that denotes the fetch state and can take the options "dry" and "green". |
This is a function to calculate the pan coefficient used in the pan evaporation method to calculate the reference evapotranspiration.
The function returns the value of the pan coefficient.
PanCoef(u_2 = 2, RH_mean = 50, FET = 3, type = "Class A", fetch = "dry")
PanCoef(u_2 = 2, RH_mean = 50, FET = 3, type = "Class A", fetch = "dry")
PsyCon
returns the value of psychrometric constant.
PsyCon(P, lambda = 2.45, c_p = 1.013 * 10^(-3), eps = 0.622)
PsyCon(P, lambda = 2.45, c_p = 1.013 * 10^(-3), eps = 0.622)
P |
A numeric scalar that denotes the atmospheric pressure [kPa]. |
lambda |
A numeric scalar that denotes the latent heat of vaporization, 2.45 [MJ/kg]. |
c_p |
A numeric scalar that denotes the specific heat at constant pressure, 1.013*10^(-3) [MJ/(kg*C). |
eps |
A numeric scalar that denotes the ratio molecular weight of water vapour/dry air = 0.622. |
This is a function to calculate the psychrometric constant [kPa/C].
The function returns the value of the psychrometric constant [kPa/C] as a numeric scalar.
PsyCon(P = 81.8)
PsyCon(P = 81.8)
RelHum
returns the value of relative humidity.
RelHum(e_a, e0T)
RelHum(e_a, e0T)
e_a |
Optional. A numeric scalar that denotes the actual vapour pressure [kPa]. |
e0T |
A numeric scalar that denotes the saturation vapour pressure at a specific air temperature [kPa]. |
This is a function to calculate the relative humidity.
The function returns the value of the relative humidity as a numeric scalar.
RelHum(e_a = 0.7, e0T = 0.9)
RelHum(e_a = 0.7, e0T = 0.9)
SatVP
returns the value of saturation vapour pressure at the air temperature Temp
[kPa].
SatVP(Temp)
SatVP(Temp)
Temp |
A numeric scalar that denotes the air temperature [C]. |
This is a function to calculate the saturation vapour pressure at the air temperature Temp
[kPa].
The function returns the value of the saturation vapour pressure at the air temperature Temp
[kPa] as a numeric scalar.
MSVP
.
SatVP(Temp = 25)
SatVP(Temp = 25)
SlpSVPC
returns the value of slope of saturation vapour pressure curve at a specific air temperature.
SlpSVPC(Temp)
SlpSVPC(Temp)
Temp |
A numeric scalar that denotes the air temperature [C]. |
This is a function to calculate the slope of saturation vapour pressure curve at the air temperature Temp
[kPa/C].
The function returns the value of the slope of saturation vapour pressure curve at air temperature Temp
as a numeric scalar.
SlpSVPC(Temp = 25)
SlpSVPC(Temp = 25)
SolDec
returns the solar declination.
SolDec(date)
SolDec(date)
date |
Optional. A character string that denotes the date in the format "Year-Month-Day" or "Year/Month/Day". |
This is a function to calculate the value of solar declination.
The function returns the value of solar declination as a numeric scalar.
SolDec("2020/08/25")
SolDec("2020/08/25")
SolRad
returns the value of solar radiation.
SolRad( n = NULL, N = NULL, a_s = 0.25, b_s = 0.5, R_a, T_max = NULL, T_min = NULL, region = NULL )
SolRad( n = NULL, N = NULL, a_s = 0.25, b_s = 0.5, R_a, T_max = NULL, T_min = NULL, region = NULL )
n |
Optional. A numeric scalar that denotes actual duration of sunshine [hour] |
N |
Optional. A numeric scalar that denotes maximum possible duration of sunshine or daylight hours [hour] |
a_s |
Optional. A numeric scalar that denotes regression constant, expressing the fraction ofextraterrestrial radiation
reaching the earth on overcast days (n = 0). The default is |
b_s |
Optional. A numeric scalar that denotes fraction of extraterrestrial radiation reaching the earth on clear days
( |
R_a |
A numeric scalar that denotes extraterrestrial radiation [ |
T_max |
Optional. A numeric scalar that denotes the daily maximum temperature [C]. |
T_min |
Optional. A numeric scalar that denotes the daily minimum temperature [C]. |
region |
A character string that introduce the type of region and can be assigned "inter" for interior locations and "coast" for coastal locations for Hargreaves radiation formula (alternative) |
This is a function to calculate the solar radiation based on the land type. If one of the arguments n
or N
is missing, the function needs to use the values of the arguments T_min
, T_max
, and region
.
If calibrated values of a_s
and b_s
are available, they can replace the default values.
The function returns the value of solar radiation based as a numeric scalar.
SolRad(n = 7.1, N = 10.9, R_a = 25.1) SolRad(R_a = 25.1, T_max = 30, T_min = 20, region = "inter")
SolRad(n = 7.1, N = 10.9, R_a = 25.1) SolRad(R_a = 25.1, T_max = 30, T_min = 20, region = "inter")
SunHA
returns the value of sunset hour angel [rad].
SunHA(phi, delta)
SunHA(phi, delta)
phi |
A numeric scalar that denotes the latitude [rad]. |
delta |
A numeric scalar that denotes the solar declination [rad]. |
This is a function to calculate the sunset hour angel.
The function returns the value of sunset hour angel as a numeric scalar.
SunHA(phi = -0.35, delta = 0.12)
SunHA(phi = -0.35, delta = 0.12)
WndSp
returns the value of wind speed at the height 2 m above the ground surface.
WndSp2m(u_z, z, speed = NULL)
WndSp2m(u_z, z, speed = NULL)
u_z |
Optional. A numeric scalar that denotes the measured wind speed at z m above ground surface [m/s]. |
z |
A numeric scalar that denotes the height of measurement above ground surface [m]. |
speed |
Optional. A character string that denotes the wind speed general class and can be assigned
|
This is a function to calculate the wind speed [m/s]. If u_z
is missing, the function estimate the
wind speed based on wind general or empirical classes.
The function returns the value of the wind speed [m/s] as a numeric scalar.
WndSp2m(u_z = 3.2, z = 10) WndSp2m(speed = "mod2str")
WndSp2m(u_z = 3.2, z = 10) WndSp2m(speed = "mod2str")