Evapotranspiration (version 1.10)

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", …)

Arguments

data

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

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.

…

Dummy for generic function, no need to define.

Value

The function prints a calculation summary to the screen containing 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.

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")
# }