# ET.Turc

##### Turc Formulation

Implementing the Turc formulation for estimating reference crop evapotranspiration.

##### Usage

```
# S3 method for Turc
ET(data, constants, ts="daily", solar="sunshine hours", humid= F, …)
```

##### Arguments

- data
A list of data which contains the following items (climate variables) required by Turc formulation:

*Tmax*,*Tmin*,*Rs*or*n*or*Cd*- constants
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.- ts
Must be either

`daily`

,`monthly`

or`annual`

, which indicates the disired time step that the output ET estimates should be on. Default is`daily`

.- solar
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`

.- humid
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.- …
Dummy for generic function, no need to define.

##### Details

The alternative calculation options can be selected through argument `solar`

, please see `Arguments`

for details.
Humidity adjustment for the estimations is available through argument `humid`

, please see `Arguments`

for details.

##### Value

The function prints a calculation summary to the screen containing 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.

The function also generates a list containing the following components, which is saved into a `csv`

file named as *ET_Turc.csv* in the working directory:

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.

##### References

McMahon, T., Peel, M., Lowe, L., Srikanthan, R. & McVicar, T. 2012. *Estimating actual, potential, reference crop and pan evaporation using standard meteorological data: a pragmatic synthesis*. Hydrology and Earth System Sciences Discussions, 9, 11829-11910.

Turc, L. 1961, *Estimation of irrigation water requirements, potential evapotranspiration: a simple climatic formula evolved up to date*. Ann. Agron, vol. 12, no. 1, pp. 13-49.

Alexandris, S., Stricevic, R.Petkovic, S. 2008, *Comparative analysis of reference evapotranspiration from the surface of rainfed grass in central Serbia, calculated by six empirical methods against the Penman-Monteith formula*. European Water, vol. 21, no. 22, pp. 17-28.

##### See Also

##### Examples

```
# NOT RUN {
# Use processed existing data set and constants from kent Town, Adelaide
data("processeddata")
data("constants")
# Call ET.Turc under the generic function ET
results <- ET.Turc(data, constants, ts="daily", solar="sunshine hours", humid= FALSE)
# }
```

*Documentation reproduced from package Evapotranspiration, version 1.10, License: GPL (>= 2)*