A list of climate data required for estimating evapotranspiration which differs for each evapotranspiration formulations, see specific formulations for details.

A list named constants consists of constants required for the ET models which mdiffer for specific ET models - refer to the manual for individual models for details.

Arguments to be passed to methods which differs for each evapotranspiration formulations, see specific formulations for details.

A list of data in class "Abtew" which contains the following items (climate variables) required by Abtew formulation:
Tmax, Tmin (degree Celcius), Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Abtew formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Abtew actual evapotranspiration.

Monthly aggregated estimations of Abtew actual evapotranspiration.

Annually aggregated estimations of Abtew actual evapotranspiration.

Monthly averaged estimations of daily Abtew actual evapotranspiration.

Annually averaged estimations of daily Abtew actual evapotranspiration.

Name of the formulation used which equals to Abtew.

Type of the estimation obtained which is Actual Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A list of data which contains the following items (climate variables) required by Blaney-Criddle formulation:
Tmax, Tmin (degree Celcius), RHmin (per cent), n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of PenPan formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
z - height of wind instrument in m,
e0,e1,e2,e3,e4 - recommended values of 0.81917, -0.0040922, 1.0705, 0.065649, -0.0059684, -0.0005967 respectively (Table 1 in Frevert et al., 1983).

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either sunshine hours or cloud:
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data.
Default is sunshine hours.

Must be T or F, indicating if adjustment for site elevation for arid and semi-arid regions is applied in Blaney-Criddle formulation (Allen and Brockway, 1983).
Default is F for no adjustment.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface
- Option for calculating solar radiation (i.e. the value of argument solar)
- If height adjustment has been applied on results (i.e. the value of argument height)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Blaney-Criddle reference crop evapotranspiration.

Monthly aggregated estimations of Blaney-Criddle reference crop evapotranspiration.

Annually ggregated estimations of Blaney-Criddle reference crop evapotranspiration.

Monthly averaged estimations of daily Blaney-Criddle reference crop evapotranspiration.

Annually averaged estimations of daily Blaney-Criddle reference crop evapotranspiration.

Name of the formulation used which equals to Blaney-Criddle.

Type of the estimation obtained which is Reference Crop Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if height adjustment has been applied to calculated Blaney-Criddle reference crop evapotranspiration.

A list of data which contains the following items (climate variables) required by Brutsaert-Strickler formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of Brutsaert-Strickler formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Any numeric value between 0 and 1 (dimensionless), albedo of the evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.23 for surface covered with short reference crop.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo, surface resistance, crop height and roughness height
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Brutsaert-Strickler actual areal evapotranspiration.

Monthly aggregated estimations of Brutsaert-Strickler actual areal evapotranspiration.

Annually aggregated estimations of Brutsaert-Strickler actual areal evapotranspiration.

Monthly averaged estimations of daily Brutsaert-Strickler actual areal evapotranspiration.

Annually averaged estimations of daily Brutsaert-Strickler actual areal evapotranspiration.

Name of the formulation used which equals to Brutsaert-Strickler.

Type of the estimation obtained which is Actual Areal Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A list of data which contains the following items (climate variables) required by Chapman formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of Chapman formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1,
lat - latitude in degrees,
alphaA - albedo for Class-A pan,
ap - a constant in PenPan = 2.4.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be T or F, indicating if the PenPan formulation is used for estimating Class-A pan evaporation required in Chapman formulation. If T PenPan will be used and if F the actual data of Class-A pan evaporation will be used. Default is T for using the PenPan formulation.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Any numeric value between 0 and 1 (dimensionless), albedo of the evaporative surface incident radiation that is reflected back at the surface.
Default is 0.23 for surface covered with short reference crop.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated, and the value of pan coefficient (only for when potential ET is estimated)
- Evaporative surface with values of albedo
- Option for calculating solar radiation (i.e. the value of argument solar)
- If the PenPan formulation is used for estimating Class-A pan evaporation required in Chapman formulation (i.e. the value of argument PenPan)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Chapman potential evapotranspiration.

Monthly aggregated estimations of Chapman potential evapotranspiration.

Annually aggregated estimations of Chapman equivalent Penmen-Monteith evapotranspiration.

Monthly averaged estimations of daily Chapman potential evapotranspiration.

Annually averaged estimations of daily Chapman potential evapotranspiration.

Name of the formulation used which equals to Chapman.

Type of the estimation obtained which is Potential Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if the Class-A pan evaporation is from actual data or from PenPan estimation.

A list of data which contains the following items (climate variables) required by Granger-Gray formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of Granger-Gray formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.
G - soil heat flux in MJ.m^-2.day^-1, = 0 when using daily time step.
The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

The version of Penman wind function that will be used within the Penman formulation. Must be either 1948 or 1956.
1948 is for applying the Penman's 1948 wind function (Penman, 1948);
1956 is for applying the Penman's 1956 wind function (Penman, 1956) Default is 1948.

Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.23 for surface covered with short reference crop.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo
- Option for calculating solar radiation (i.e. the value of argument solar)
- The version of Penman wind function has been used (i.e. the value of argument windfunction_ver)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Granger-Gray actual areal evapotranspiration.

Monthly aggregated estimations of Granger-Gray actual areal evapotranspiration.

Annually aggregated estimations of Granger-Gray actual areal evapotranspiration.

Monthly averaged estimations of daily Granger-Gray actual areal evapotranspiration.

Annually averaged estimations of daily Granger-Gray actual areal evapotranspiration.

Name of the formulation used which equals to Granger-Gray.

Type of the estimation obtained which is Actual Areal Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about which version of the Penman wind function has been used.

A list of data which contains the following items (climate variables) required by Hamon formulation:
Tmax, Tmin (degree Celcius), n (hour)

Dummy argument with a NULL value.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Hamon potential evapotranspiration.

Monthly aggregated estimations of Hamon potential evapotranspiration.

Annually aggregated estimations of Hamon potential evapotranspiration.

Monthly averaged estimations of daily Hamon potential evapotranspiration.

Annually averaged estimations of daily Hamon potential evapotranspiration.

Name of the formulation used which equals to Hamon.

Type of the estimation obtained which is Potential Evapotranspiration.

A list of data which contains the following items (climate variables) required by Hargreaves-Samani formulation: Tmax, Tmin (degree Celcius)

A list named constants consists of constants required for the calculation of Hargreaves-Samani formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Hargreaves-Samani reference crop evapotranspiration.

Monthly aggregated estimations of Hargreaves-Samani reference crop evapotranspiration.

Annually aggregated estimations of Hargreaves-Samani reference crop evapotranspiration.

Monthly averaged estimations of daily Hargreaves-Samani reference crop evapotranspiration.

Annually averaged estimations of daily Hargreaves-Samani reference crop evapotranspiration.

Name of the formulation used which equals to Hargreaves-Samani.

Type of the estimation obtained which is Reference Crop Evapotranspiration.

A list of data which contains the following items (climate variables) required by Jensen-Haise formulation: Tmax, Tmin, Rs or n or Cd Tmax, Tmin (degree Celcius), Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Jensen-Haise formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Jensen-Haise potential evapotranspiration.

Monthly aggregated estimations of Jensen-Haise potential evapotranspiration.

Annually aggregated estimations of Jensen-Haise potential evapotranspiration.

Monthly averaged estimations of daily Jensen-Haise potential evapotranspiration.

Annually averaged estimations of daily Jensen-Haise potential evapotranspiration.

Name of the formulation used which equals to Jensen-Haise.

Type of the estimation obtained which is Potential Evapotranspiration.

A list of data which contains the following items (climate variables) required by Linacre formulation:
Tmax, Tmin, Tdew (degree Celcius)

A list named constants consists of constants required for the calculation of Linacre formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lat - latitude in degrees.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Linacre actual evapotranspiration.

Monthly aggregated estimations of Linacre actual evapotranspiration.

Annually aggregated estimations of Linacre actual evapotranspiration.

Monthly averaged estimations of daily Linacre actual evapotranspiration.

Annually averaged estimations of daily Linacre actual evapotranspiration.

Name of the formulation used which equals to Linacre.

Type of the estimation obtained which is Actual Evapotranspiration.

A list of data which contains the following items (climate variables) required by Makkink formulation:
Tmax, Tmin (degree Celcius), Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Makkink formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Makkink reference crop evapotranspiration.

Monthly aggregated estimations of Makkink reference crop evapotranspiration.

Annually aggregated estimations of Makkink reference crop evapotranspiration.

Monthly averaged estimations of daily Makkink reference crop evapotranspiration.

Annually averaged estimations of daily Makkink reference crop evapotranspiration.

Name of the formulation used which equals to Makkink.

Type of the estimation obtained which is Reference crop evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A list which contains the following items (climate variables) required by Matt-Shuttleworth formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of Matt-Shuttleworth formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1,
Roua - mean air density = 1.20 kg.m^-3,
Ca - specific heat of air = 0.001013 MJ.kg^-1.oC^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.23 for surface covered with short reference crop, which is for the calculation of Matt-Shuttleworth reference crop evaporation.

Any value (seconds per metre), surface resistance depends on the type of reference crop.
Default is 70 for short reference crop.

Any value (metres), crop height depends on the reference crop.
Default is 0.12 for short reference crop.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo, surface resistance and crop height
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Matt-Shuttleworth reference crop evapotranspiration.

Monthly aggregated estimations of Matt-Shuttleworth reference crop evapotranspiration.

Annually aggregated estimations of Matt-Shuttleworth reference crop evapotranspiration.

Monthly averaged estimations of daily Matt-Shuttleworth reference crop evapotranspiration.

Annually averaged estimations of daily Matt-Shuttleworth reference crop evapotranspiration.

Name of the formulation used which equals to Matt-Shuttleworth.

Type of the estimation obtained which is Reference Crop Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A list of data which contains the following items (climate variables) required by McGuinness-Bordne formulation: Tmax, Tmin (degree Celcius)

A list named constants consists of constants required for the calculation of Jensen-Haise formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of McGuinness-Bordne potential evapotranspiration.

Monthly aggregated estimations of McGuinness-Bordne potential evapotranspiration.

Annually aggregated estimations of McGuinness-Bordne potential evapotranspiration.

Monthly averaged estimations of daily McGuinness-Bordne potential evapotranspiration.

Annually averaged estimations of daily McGuinness-Bordne potential evapotranspiration.

Name of the formulation used which equals to McGuinness-Bordne.

Type of the estimation obtained which is Potential Evapotranspiration.

A list of data which contains the following items (climate variables) required by Morton CRAE formulation:
Tmax, Tmin, Tdew (degree Celcius) or va or RHmax and RHmin, Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Morton CRAE formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lat_rad - latitude in radians,
PA - annual precipitation in mm, required when precipitation data is not available,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1,
lat - latitude in degrees,
epsilonMo - surface emissivity = 0.92 (Morton, 1986),
fz - A constant in Morton's procedure = 28.0 Wm^-2.mbar^-1 for T >= 0 degree Celcius, and = 28.0*1.15 Wm^-2.mbar^-1 for T >= 0 degree Celcius for CRAE model (Morton, 1983),
b0 - a constants in Morton's procedure, = 1 for CRAE model (Morton, 1983),
b1 - a constant in Morton's procedure, = 14 for CRAE model (Morton, 1983),
b2 - a constant in Morton's procedure, = 1.2 for CRAE model (Morton, 1983),
gammaps - Produce of Psychrometric constant and atmospheric pressure as sea level, = 0.66 mbar. degree Celcius^-1 for T >= 0 degree Celcius, = 0.66/1.15 mbar. degree Celcius^-1 for T < 0 degree Celcius (Morton, 1983),

alphaMo - a constant in Morton's procedure, = 17.27 when T >= 0 degree Celcius, = 21.88 when T < 0 degree Celcius (Morton, 1983),
betaMo - a constant in Morton's procedure, = 237.3 degree Celcius when T >= 0 degree Celcius, = 265.5 degree Celcius, when T < 0 degree Celcius (Morton, 1983),
sigmaMo - Stefan-Boltzmann constant in Morton's procedure, = 5.67e-08 W.m^-2.K^-4 (Morton, 1983),
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,

Must be either monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is monthly.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either potential ET, wet areal ET or actual areal ET:
potential ET proceeds to estimating potential evapotranspiration;
wet areal ET proceeds to estimating wet-environmental areal evapotranspiration;
actual areal ET proceeds to estimating actual areal evapotranspiraion.
Default is potential ET.

Must be T or F, indicating if real data of dew point temperature is used for calculating the radiation in Morton's formulations, if T the data will be used and if F the dew point temperature will be calculated from data of daily vapour pressure. Default is T for using actual dew point temperature data.

Only needed if argument solar has value of data.
Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is NULL in line with the default use of sunshine hours to estimate solar radiation (i.e. argument solar is sunshine hours.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated (i.e. the value of argument est)
- Option for calculating solar radiation (i.e. the value of argument solar)
- If the actual dew point temperature data are used (i.e. the value of argument Tdew)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Morton CRAE potential evapotranspiration, wet-environment areal evapotranspiration or actual areal evapotranspiration.

Monthly aggregated estimations of Morton CRAE potential evapotranspiration, wet-environment areal evapotranspiration or actual areal evapotranspiration.

A zoo object containing annually aggregated estimations of Morton CRAE potential evapotranspiration, wet-environment areal evapotranspiration or actual areal evapotranspiration.

A zoo object containing monthly averaged estimations of daily Morton CRAE potential evapotranspiration, wet-environment areal evapotranspiration or actual areal evapotranspiration.

A zoo object containing annually averaged estimations of daily Morton CRAE potential evapotranspiration, wet-environment areal evapotranspiration or actual areal evapotranspiration.

Name of the formulation used which equals to MortonCRAE.

Type of the estimation obtained which is either Potential Evapotranspiration, Wet-environment Areal Evapotranspiration and Actual Areal Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if actual dew point temperature has been used in the calculations or alternative calculations has been performed without dew point temperature data.

A list of data which contains the following items (climate variables) required by Morton CRWE formulation:
Tmax, Tmin, Tdew (degree Celcius) or va or RHmax and RHmin, Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Morton CRWE formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lat_rad - latitude in radians,
PA - annual precipitation in mm, required when precipitation data is not available,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1,
lat - latitude in degrees,
epsilonMo - surface emissivity = 0.92 (Morton, 1986),
fz - A constant in Morton's procedure = 25.0 Wm^-2.mbar^-1 for T >= 0 degree Celcius, and = 28.75 Wm^-2.mbar^-1 for T >= 0 degree Celcius for CRWE model (Morton, 1986),
b0 - A constants in Morton's procedure, = 1.12 for CRWE model, (Morton, 1986) b1 - A constant in Morton's procedure, = 13 for CRWE model (Morton, 1986),
b2 - A constant in Morton's procedure, = 1.12 for CRWE model (Morton, 1986),
gammaps - Produce of Psychrometric constant and atmospheric pressure as sea level, = 0.66 mbar. degree Celcius^-1 for T >= 0 degree Celcius, = 0.66/1.15 mbar. degree Celcius^-1 for T < 0 degree Celcius (Morton, 1983),

alphaMo - a constant in Morton's procedure, = 17.27 when T >= 0 degree Celcius, = 21.88 when T < 0 degree Celcius (Morton, 1983),
betaMo - a constant in Morton's procedure, = 237.3 degree Celcius when T >= 0 degree Celcius, = 265.5 degree Celcius, when T < 0 degree Celcius (Morton, 1983),
sigmaMo - Stefan-Boltzmann constant in Morton's procedure, = 5.67e-08 W.m^-2.K^-4 (Morton, 1983),
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,

Must be either monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is monthly.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either potential ET or shallow lake ET:
potential ET proceeds to estimating potential evapotranspiration;
shallow lake ET proceeds to estimating shallow lake evaporation.
Default is potential ET.

Must be T or F, indicating if real data of dew point temperature is used for calculating the radiation in Morton's formulations, if T the data will be used and if F the dew point temperature will be calculated from data of daily vapour pressure. Default is T for using actual dew point temperature data.

Only needed if argument solar has value of data.
Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is NULL in line with the default use of sunshine hours to estimate solar radiation (i.e. argument solar is sunshine hours.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated (i.e. the value of argument est)
- Option for calculating solar radiation (i.e. the value of argument solar)
- If the actual dew point temperature data are used (i.e. the value of argument Tdew)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of MortonCRWE potential evapotranspiration or shallow lake evaporation.

Monthly aggregated estimations of MortonCRWE potential evapotranspiration or shallow lake evaporation.

Annually aggregated estimations of MortonCRWE potential evapotranspiration or shallow lake evaporation.

Monthly averaged estimations of daily MortonCRWE potential evapotranspiration or shallow lake evaporation.

Annually averaged estimations of daily MortonCRWE potential evapotranspiration or shallow lake evaporation.

Name of the formulation used which equals to MortonCRWE.

Type of the estimation obtained which is either Potential Evapotranspiration or Shallow Lake Evaporation.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if actual dew point temperature has been used in the calculations or alternative calculations has been performed without dew point temperature data.

A list of data which contains the following items (climate variables) required by PenPan formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of PenPan formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1,
lat - latitude in degrees,
alphaA - albedo for Class-A pan,
ap - a constant in PenPan = 2.4.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Any numeric value between 0 and 1 (dimensionless), albedo of surface surrounding the evaporation pan representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.23 for surface covered with short reference crop.

Must be T or F, indicating if adjustment for the overestimation (i.e. divided by 1.078) of Class-A pan evaporation for Australian data is applied in PenPan formulation.
Default is F for no adjustment.

Must be either pan or potential ET to specify if estimation for the Class-A pan evaporation or potential evapotranspriation is performed.
Default is potential ET for estimating potential evapotranspriation.

Only required if argument est has value of potential ET, which defines the pan coefficient used to adjust the estimated pan evaporation to the potential ET required.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated (i.e. the value of argument est), and the value of pan coefficient (only for when potential ET is estimated)
- Evaporative surface with values of albedo
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of PenPan Class-A pan evaporation/potential evapotranspiration.

Monthly aggregated estimations of PenPan Class-A pan evaporation/potential evapotranspiration.

Annually aggregated estimations of PenPan Class-A pan evaporation/potential evapotranspiration.

Monthly averaged estimations of daily PenPan Class-A pan evaporation/potential evapotranspiration.

Annually averaged estimations of daily PenPan Class-A pan evaporation/potential evapotranspiration.

Name of the formulation used which equals to PenPan.

Type of the estimation obtained which is Class-A Pan Evaporation or Potential Evapotranspiration depending on the value of est.

A message to inform the users about how solar radiation has been calculated by using which data.

A list which contains the following items (climate variables) required by Penman formulation:
Tmax, Tmin, RHmax, RHmin, Rs or n or Cd, u2 or uz

A list named constants consists of constants required for the calculation of Penman formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - only for when cloud data is used for calculating radiation i.e. solar = "cloud" - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - only for when cloud data is used for calculating radiation i.e. solar = "cloud" - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either yes or no.
yes indicates that the calculation will use real data of wind speed;
no indicates that the alternative calculation without using wind data will be used in Penman formulation (Valiantzas 2006, Equation33).
Default is yes.

The version of Penman wind function that will be used within the Penman formulation. Must be either 1948 or 1956.
1948 is for applying the Penman's 1948 wind function (Penman, 1948);
1956 is for applying the Penman's 1956 wind function (Penman, 1956) Default is 1948.

Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.08 for open-water surface which is for the calculation of Penman open-water evaporation, all other values will trigger the calculation of Penman potential evapotranspriation.

Any value (metres), roughness height of the evaporative surface.
Default is 0.001 for open-water surface which is for the calculation of Penman open-water evaporation, all other values will trigger the calculation of Penman potential evapotranspriation.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo and roughness height
- Option for calculating solar radiation (i.e. the value of argument solar)
- If actual wind data has been used for calculation (i.e. the value of argument wind) and which version of Penman wind function has been used (i.e. the value of argument windfunction_ver)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Penman open-water evaporation or potential evapotranspiration.

Monthly aggregated estimations of Penman open-water evaporation or potential evapotranspiration.

Annually aggregated estimations of Penman open-water evaporation or potential evapotranspiration.

Monthly averaged estimations of daily Penman open-water evaporation or potential evapotranspiration.

Annually averaged estimations of daily Penman open-water evaporation or potential evapotranspiration.

Name of the formulation used which equals to Penman.

Type of the estimation obtained which is either Open-water Evaporation or Potential Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if actual wind data has been used in the calculations or alternative calculations has been performed without wind data, and which version of the Penman wind function has been used.

A list which contains the following items (climate variables) required by Penman-Monteith formulation:
Tmax, Tmin, RHmax, RHmin, Rs or n or Cd, u2 or uz

A list named constants consists of constants required for the calculation of Penman-Monteith formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.
G - soil heat flux in MJ.m^-2.day^-1, = 0 when using daily time step.
The following constants are also required when argument solar has value of sunshine hours:
as - only for when cloud data is used for calculating radiation i.e. solar = "cloud" - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - only for when cloud data is used for calculating radiation i.e. solar = "cloud" - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either yes or no.
yes indicates that the calculation will use real data of wind speed;
no indicates that the alternative calculation without using wind data will be used in Penman formulation (Valiantzas 2006, Equation33).
Default is yes.

Must be either short or tall.
short indicates that the method for FAO-56 hypothetical short grass will be applied (Allen et al., 1998, Equation 6);
tall indicates that the method for ASCE-EWRI Standardised crop will be applied (ASCE, 2005, Equation 1, Table 1).
Default is short.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo, surface resistance, crop height and roughness height
- Option for calculating solar radiation (i.e. the value of argument solar)
- If actual wind data has been used for calculation (i.e. the value of argument wind)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Penman-Monteith rerference crop evapotranspiration.

Monthly aggregated estimations of Penman-Monteith rerference crop evapotranspiration.

Annually aggregated estimations of Penman-Monteith rerference crop evapotranspiration.

Monthly averaged estimations of daily Penman-Monteith rerference crop evapotranspiration.

Annually averaged estimations of daily Penman-Monteith rerference crop evapotranspiration.

Name of the formulation used which equals to either Penman-Monteith FAO56 or Penman-Monteith ASCE-EWRI Standardised.

A character string containing the type of the estimation obtained which is Reference Crop Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if actual wind data has been used in the calculations or alternative calculations has been performed without wind data.

A list which contains the following items (climate variables) required by Priestley-Taylor formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Priestley-Taylor formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1,
alphaPT - Priestley-Taylor coefficient = 1.26 for Priestley-Taylor model (Priestley and Taylor, 1972)
G - soil heat flux in MJ.m^-2.day^-1, = 0 when using daily time step.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.23 for surface covered with short reference crop, which is for the calculation of Priestly-Taylor reference crop evaporation.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo
- Option for calculating solar radiation (i.e. the value of argument solar)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Priestley-Taylor potential evaporation.

Monthly aggregated estimations of Priestley-Taylor potential evaporation.

Annually aggregated estimations of Priestley-Taylor potential evaporation.

Monthly averaged estimations of daily Priestley-Taylor potential evaporation.

Annually averaged estimations of daily Priestley-Taylor potential evaporation.

A character string containing the name of the formulation used which equals to Priestley-Taylor.

Type of the estimation obtained which is Potential Evaporation.

A message to inform the users about how solar radiation has been calculated by using which data.

A list of data which contains the following items (climate variables) required by Romanenko formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent)

Dummy argument with a NULL value.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Romanenko potential evapotranspiration.

Monthly aggregated estimations of Romanenko potential evapotranspiration.

Annually aggregated estimations of Romanenko potential evapotranspiration.

Monthly averaged estimations of daily Romanenko potential evapotranspiration.

Annually averaged estimations of daily Romanenko potential evapotranspiration.

Name of the formulation used which equals to Romanenko.

Type of the estimation obtained which is Potential Evapotranspiration.

A list of data which contains the following items (climate variables) required by Szilagyi-Jozsa formulation:
Tmax, Tmin (degree Celcius), RHmax, RHmin (per cent), Rs (Megajoules per sqm) or n (hour) or Cd (okta), u2 or uz (meter per second)

A list named constants consists of constants required for the calculation of Szilagyi-Jozsa formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
z - height of wind instrument in m,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be either yes or no.
yes indicates that the calculation will use real data of wind speed;
no indicates that the alternative calculation without using wind data will be used in Penman formulation (Valiantzas 2006, Equation33), which is required in the Szilagyi-Jozsa model.
Default is yes.

The version of Penman wind function that will be used within the Penman formulation. Must be either 1948 or 1956.
1948 is for applying the Penman's 1948 wind function (Penman, 1948);
1956 is for applying the Penman's 1956 wind function (Penman, 1956) Default is 1948.

Any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface representing the portion of the incident radiation that is reflected back at the surface.
Default is 0.23 for short reference crop.

Any value (metres), roughness height of the evaporative surface.
Default is 0.23 for short reference crop.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface with values of albedo, as well as the roughness height
- Option for calculating solar radiation (i.e. the value of argument solar)
- If actual wind data has been used for calculation (i.e. the value of argument wind) and which version of Penman wind function has been used (i.e. the value of argument windfunction_ver)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Szilagyi-Jozsa actual evapotranspiration.

Monthly aggregated estimations of Szilagyi-Jozsa actual evapotranspiration.

Annually aggregated estimations of Szilagyi-Jozsa actual evapotranspiration.

Monthly averaged estimations of daily Szilagyi-Jozsa actual evapotranspiration.

Annually averaged estimations of daily Szilagyi-Jozsa actual evapotranspiration.

Name of the formulation used which equals to Szilagyi-Jozsa.

A character string containing the type of the estimation obtained which is Actual Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if actual wind data has been used in the calculations or alternative calculations has been performed without wind data, and which version of the Penman wind function has been used.

A list of data which contains the following items (climate variables) required by Turc formulation:
Tmax, Tmin (degree Celcius), Rs (Megajoules per sqm) or n (hour) or Cd (okta)

A list named constants consists of constants required for the calculation of Turc formulation which must contain the following items:
Elev - ground elevation above mean sea level in m,
lambda - latent heat of vaporisation = 2.45 MJ.kg^-1,
lat_rad - latitude in radians,
Gsc - solar constant = 0.0820 MJ.m^-2.min^-1,
sigma - Stefan-Boltzmann constant = 4.903*10^-9 MJ.K^-4.m^-2.day^-1.

The following constants are also required when argument solar has value of sunshine hours:
as - fraction of extraterrestrial radiation reaching earth on sunless days,
bs - difference between fracion of extraterrestrial radiation reaching full-sun days and that on sunless days.

Must be either daily, monthly or annual, which indicates the disired time step that the output ET estimates should be on. Default is daily.

Must be either data, sunshine hours, cloud or monthly precipitation:
data indicates that solar radiation data is to be used directly for calculating evapotranspiration;
sunshine hours indicates that solar radiation is to be calculated using the real data of sunshine hours;
cloud sunshine hours is to be estimated from cloud data;
monthly precipitation indicates that solar radiation is to be calculated directly from monthly precipitation.
Default is sunshine hours.

Must be T or F, indicating if adjustment for non-humid conditions is applied in Turc formulation (Alexandris et al., 2008, Equation 5b).
Default is F for no adjustment.

Must be either yes or no, indicating whether message should be printed for calculation summary including the following elements:
- ET model name and ET quantity estimated
- Evaporative surface
- Option for calculating solar radiation (i.e. the value of argument solar)
- if adjustment for non-humid conditions has been applied (i.e. the value of argument humid)
- Time step of the output ET estimates (i.e. the value of argument ts)
- Units of the output ET estimates
- Time duration of the ET estimation
- Number of ET estimates obtained in the entire time-series
- Basic statistics of the estimated ET time-series including mean, max and min values.

"yes" or "no" indicating whether monthly averaged and annual averaged ET should be calculated.

Must be either yes or no, indicating whether a .csv of ET estimates should be saved to working directory.

Dummy for generic function, no need to define.

Daily aggregated estimations of Turc reference crop evapotranspiration.

Monthly aggregated estimations of Turc reference crop evapotranspiration.

Annually aggregated estimations of Turc reference crop evapotranspiration.

Monthly averaged estimations of daily Turc reference crop evapotranspiration.

Annually averaged estimations of daily Turc reference crop evapotranspiration.

Name of the formulation used which equals to Turc.

Type of the estimation obtained which is Reference Crop Evapotranspiration.

A message to inform the users about how solar radiation has been calculated by using which data.

A message to inform the users about if adjustment for non-humid conditions has been applied to calculated Turc reference crop evapotranspiration.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.
The default is NULL if the user requires the comparison between only two sets of results.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.
The default is NULL if the user requires the comparison among only three sets of results.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.
The default is NULL if the user requires the comparison among only four sets of results.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.
The default is NULL if the user requires the comparison among only five sets of results.

A list named results which has been derived from function ET which can be from any model such as Penman, Penman-Monteith or Priestley-Taylor.
The default is NULL if the user requires the comparison among only six sets of results.

A character vector with the length equal to the number of sets of results to compare, defining the labels for the comparison plots

Only used when argument type is Daily, Monthly or Annual to define the start date for the plotting windows, which can be defined by user in the format YYYY-MM-DD; if missing the default is the first day of data is used.

Only used when argument type is Daily, Monthly or Annual to define the end date for the plotting windows, which can be defined by user in the format YYYY-MM-DD; if missing the default is the last day of data is used.

A numeric vector of length 2 defining the lower and upper limit of the y-axis for plotting, if missing the default is from 0 to 1.5 times of maximum value from the first set of result that is used to compare with others.

A character string indicating the type of plot produced, can be one of the following:
Daily - comparison plots of estimated daily evapotranspiration;
Monthly - comparison plots of monthly aggregated evapotranspiration;
Annual - comparison plots of annually aggregated evapotranspiration;
MonthlyAve - comparison plots of monthly averaged daily evapotranspiration;
AnnualAve - comparison plots of annually averaged daily evapotranspiration.

A list of data named data which must contain a component with the name of a climate variable that the estimated evapotranspiration should be plotted against, see forcing.

A list named results which has been derived from function ET.

A character string as the name of a climate variable that the estimated evapotranspiration should be plotted against, can be any of:
Tmax - maximum temperature,
Tmin - minimum temperature,
u2 - average wind speed at 2m,
uz - average wind speed,
Rs - solar radiation,
n - daily sunshine hours,
Precip - precipitation,
Epan - Class-A pan evaporation,
RHmax - maximum relative humidity,
RHmin - minimum relative humidity,
Tdew - average dew point temeprature.

A list named results which has been derived from function ET..().

A character string of either Aggregation or Average to indicate the type of plot required. The default is Aggregation. For aggregation plot the user can define the start and end date of plotting or by default using the calculation period for plotting. For average plot the plotting period equals to the calculation period.

A list named OBS which has been derived from function ReadOBSEvaporation.

Must be eith TRUE or FALSE. TRUE indicates that the observed evaporation will be plotted together with the estimations and FALSE indicates that the observations will not be shown on the plots.

Only used when type = Aggregation to define the start date for the plotting windows, the default is the first day for the estimate evapotranspiration, but can be defined by user in the format YYYY-MM-DD.

Only used when type = Aggregation to define the end date for the plotting windows, the default is the last day for the estimate evapotranspiration, but can be defined by user in the format YYYY-MM-DD.

A character vector with length equals to the number of climate variables to be processed. Can include any element from: Tmax, Tmin, Temp, Tdew, RHmax, RHmin, RH, Rs, n, Cd, Precip, uz, u2, Epan, va, vs.

Each variable is detailed as below:

Tmax - daily maximum temperature in degree Celcius,
Tmin - daily minimum temperature in degree Celcius,
Temp - subdaily temperature in degree Celcius
Tdew - dew point temperature in degree Celcius, either daily or subdaily accepted,
RHmax - daily maximum relative humidity in percentage,
RHmin - daily minimum relative humidity in percentage,
RH - subdaily relative humidity in percentage,
Rs - incoming solar radiation in Megajoules per square metres per day, either daily or subdaily accepted,
n - daily sunshine hour in hours,
Cd - daily cloud cover in oktas,
Precip - precipitation in millimitres, either daily or subdaily accepted,
u2 - wind speed measured at 2 metres from the ground surface in metres per second, either daily or subdaily accepted,
uz - wind speed in metres per second, either daily or subdaily accepted,
Epan - daily Class-A pan evaporation in millimitres,
va - average vapour pressure in KPa, either daily or subdaily accepted,
vs - saturated vapour pressure in KPa, either daily or subdaily accepted.

A data frame named "climatedata" containing the raw data of date and climate variables.
The data frame must have objects named as Year, Month and Day to indicate the date.
The climate variables to include should be consistent with varnames.
In order to determine which variables are needed for ET estimation, please see ET for the specific data requirements for different formulations.

Should be either daily or subdaily to specify the time step of raw climate data used.

A list named "constants" consists of constants required for data pre-processing which may contain the following items:
a_0, b_0, c_0, d_0.
These four constants which are constants required to calculate daily sunshine hours from daily cloud cover (see Equation S3.10 in McMahon et al., 2012) - if the user requires such calculation these constants must be included in "constants".
The suggested values for various Australian locations are presented in Chiew and McMahon (1991), in which the four constants are named as a0, b0, c0, d0.

A numeric vector of length 3:
- the first value represents the maximum percentage of missing data that the user can tolerate;
- the second value represents the maximum percentage of the duration of missing data to the total data duaration that the user can toleratre;
- the third value represents the maximum percentage of missing days (within the date data, as a fraction of the total number of days) that the user can tolerate.
All values should be numbers between 1 and 99.
The percentages of the number and duration of missing data in the date data and each input variable are compared to the corresponding threshold; if any of the threshold is exceeded the program will be terminated due to unsatisfactory data quality.

T or F, indicating if missing days (within the date data) should be interpolated, with a default of F which assigns NA to data at the missing days.

T or F, indicating if missing data entries within individual climate variables should be interpolated, with a default of F which assigns NA to the missing entries.

T or F, if abnormal values within individual climate variables should be interpolated, with a default of F which leaves the abnormal values unchanged.
Abnormal values are defined differently according to the input variable, as following:

- Tmax > 100 or < -50 degree Celcius
- Tmin > Tmax or < -50 degree Celcius
- Temp > 100 or < -50 degree Celcius
- Tdew > 100 or < -50 degree Celcius
- RHmax > 100 or < 0 per cent
- RHmin > RHmax or < 0 per cent
- RH > 100 per cent
- Rs < 0 MJ.m^2
- n < 0 hour
- Cd < 0 Okta
- Precip < 0 mm
- uz < 0 m/s
- u2 < 0 m/s
- Epan < 0 mm
- vs < 0 KPa
- va < 0 KPa

A character string for the name of the interpolated methods chosen for filling in missing days and missing data entries. Can be either:

monthly average - replacement with same-month average (adapted from Narapusetty et al., 2009);
seasonal average - replacement with same-season average (adapted from Narapusetty et al., 2009);
DoY average - replacement with same day-of-the-year average (Narapusetty et al., 2009);
neighbouring average - interpolation between the two bounding values, which is only suitable for time increments in which values are available at adjacent increments (McMahon et al., 2013). When there is more than one consecutive missing entry, this interpolation fails, with a warning given.

A character string for the name of the interpolated methods chosen for replacing data entries with abnormal values. Can be either:

monthly average - replacement with same-month average (adapted from Narapusetty et al., 2009);
seasonal average - replacement with same-season average (adapted from Narapusetty et al., 2009);
DoY average - replacement with same day-of-the-year average (Narapusetty et al., 2009);
neighbouring average - interpolation between the two bounding values, which is only suitable for time increments in which non-abnormal values are available at adjacent increments (McMahon et al., 2013). When there is more than one consecutive abnormal entry, this interpolation fails, with a warning given.

"yes" or "no" indicating whether checking messages should be printed on screen.

A zoo object containing the date in daily step in the format of yyyy-mm-dd.

A zoo object containing the date in daily step in the format of mmm-yyyy.

A zoo object containing the Julian Day for every day during the period that the data spans.

A zoo object containing the month number for every day during the period that the data spans.

A zoo object containing the number of days for every month during the period that the data spans.

A zoo object containing the daily maximum temperatures in degree Celcius.

A zoo object containing the daily minimum temperatures in degree Celcius.

A zoo object containing the daily wind speed at 2m from the ground in m/s.

A zoo object containing the daily wind speed measured at the height of wind instrument in m/s.

A zoo object containing the daily solar radiation in MJ/m^2/day.

A zoo object containing the daily sunshine hours.

A zoo object containing the daily cloud cover in oktas.

A zoo object containing the daily precipitation in mm.

A zoo object containing the daily Class-A pan evaporation in mm.

A zoo object containing the daily maximum relative humidity in percentage.

A zoo object containing the daily minimum relative humidity in percentage.

A zoo object containing the average daily dew temperatures in degree Celcius.

A list of evaporation data named E_OBS which must contain the following columns:
Year, Month, Day as the date and,
EVAP.Obs as the observed evaporation in mm.
The observations can be of daily and monthly time steps and must match with the corresponding dates recorded.

A list of data named data which contains data of climate variables over the same period as the evaporation data

A zoo object containing the date data with time step consistent with the raw evaporation data in E_OBS.

A zoo object containing the daily evaporation data.

A zoo object containing the monthly aggregaated observed evaporation in mm.

A zoo object containing the annually aggregated observed evaporation in mm.

A zoo object containing the monthly averaged daily evaporation from observation in mm/day.

A zoo object containing the annually average daily evaporation from observation in mm/day.