# ET.BrutsaertStrickler

##### Brutsaert-Strickler Formulation

Implementing the Brutsaert-Strickler formulation for actual areal evapotranspiration

##### Usage

```
# S3 method for BrutsaertStrickler
ET(data, constants, ts="daily", solar="sunshine hours", alpha=0.23,
message="yes", AdditionalStats="yes", save.csv="yes", …)
```

##### Arguments

- data
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)- constants
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.- 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`

.- alpha
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.

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

- save.csv
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.

##### Details

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

, please see `Arguments`

for details.
User-defined evaporative surface is allowed through argument `alpha`

, please see `Arguments`

for details.

##### Value

The function also generates a list containing the following components:

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.

##### 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.

##### See Also

##### Examples

```
# NOT RUN {
# Use processed existing data set and constants from kent Town, Adelaide
data("processeddata")
data("constants")
# Call ET.BrutsaertStrickler under the generic function ET
results <- ET.BrutsaertStrickler(data, constants, ts="daily", solar="sunshine hours",
alpha=0.23, message="yes", AdditionalStats="yes", save.csv="yes")
# }
```

*Documentation reproduced from package Evapotranspiration, version 1.14, License: GPL (>= 2)*