Evapotranspiration (version 1.14)

ET.HargreavesSamani: Hargreaves-Samani Formulation

Description

Implementing the Hargreaves-Samani formulation for estimating reference crop evapotranspiration.

Usage

# S3 method for HargreavesSamani
ET(data, constants, ts="daily",
message="yes", AdditionalStats="yes", save.csv="yes", …)

Arguments

data

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

constants

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.

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.

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 - 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.

Value

The function generates a list containing the following components:

ET.Daily

Daily aggregated estimations of Hargreaves-Samani reference crop evapotranspiration.

ET.Monthly

Monthly aggregated estimations of Hargreaves-Samani reference crop evapotranspiration.

ET.Annual

Annually aggregated estimations of Hargreaves-Samani reference crop evapotranspiration.

ET.MonthlyAve

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

ET.AnnualAve

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

ET_formulation

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

ET_type

Type of the estimation obtained which is Reference Crop Evapotranspiration.

Details

This formulation provides a single calculation method with no alternatives available.

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.

Hargreaves, G.H.Samani, Z.A. 1985, Reference crop evapotranspiration from ambient air temperature. American Society of Agricultural Engineers.

See Also

ET,data,defaultconstants,constants

Examples

# NOT RUN {
# Use processed existing data set and constants from kent Town, Adelaide
data("processeddata")
data("constants")

# Call ET.HargreavesSamani under the generic function ET
results <- ET.HargreavesSamani(data, constants, ts="daily", message="yes", 
AdditionalStats="yes", save.csv="yes")
# }