ET.MortonCRWE: Morton CRWE Formulation

Description

Implementing the Morton CRWE formulation for estimating potential evapotranspiration or shallow lake evaporation.

Usage

## S3 method for class 'MortonCRWE':
ET(data, constants, est, solar, Tdew, alpha=NULL, \dots)

Arguments

data

A list of data in class "MortonCRWE" which contains the following items (climate variables) required by Morton CRWE formulation: "Tmax", "Tmin", "Tdew", "n" or "Cd".

constants

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 pre

solar

Must be either "sunshine hours" or "data". "sunshine hours" indicates that solar radiation is to be calculated using the real data of sunshine hours; "data" indicates that direct solar radiation measurements are used.

est

Must be either "potential" or "shallow lake". "potential" proceeds to estimating potential evapotranspiration; "shallow lake" proceeds to estimating shallow lake evaporation.

Tdew

Logical, must be either TRUE or FALSE, indicating if real data of dew point temperature is used for calculating the radiation in Morton's formulations, if TRUE the data will be used and if FALSE the dew point temperature will be calculated from data of da

alpha

Only needed if solar == "data". Can be any numeric value between 0 and 1 (dimensionless), albedo of evaporative surface (or surrounding surface for Penpan formulation) representing the portion of the incident radiation that is reflected back at the surfac

...

Dummy for generic function, no need to define.

Value

This function returns a object of class MortonCRWE. Such objects are list with components:
ET.DailyA zoo object containing daily aggregated estimations of MortonCRWE potential evapotranspiration or shallow lake evaporation.
ET.MonthlyA zoo object containing monthly aggregated estimations of MortonCRWE potential evapotranspiration or shallow lake evaporation.
ET.AnnualA zoo object containing annually aggregated estimations of MortonCRWE potential evapotranspiration or shallow lake evaporation.
ET.MonthlyAveA zoo object containing monthly averaged estimations of daily MortonCRWE potential evapotranspiration or shallow lake evaporation.
ET.AnnualAveA zoo object containing annually averaged estimations of daily MortonCRWE potential evapotranspiration or shallow lake evaporation.
ET_formulationA character string containing the name of the formulation used which equals to "MortonCRWE".
ET_typeA character string containing the type of the estimation obtained which is either "Potential Evapotranspiration" or "Shallow Lake Evaporation".
message1A message to inform the users about how solar radiation has been calculated by using which data.
message6A 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.

Details

The type of evapotranspiration calculated can be selected through argument est, please see "Arguments" for details. The alternative calculation options can be selected through argument solar and Tdew, please see "Arguments" for details.

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. MORTON, F. I. 1986. Practical Estimates of Lake Evaporation. Journal of Applied Meteorology, 25, 371-388.

Examples

Run this code

# Use processed existing data set from kent Town, Adelaide
data("processeddata")
data("constants")

# Set data class to be "MortonCRWE" to call function
funname <- "MortonCRWE" 
class(data) <- funname 

# Call generic function ET(data, ...) with class "MortonCRWE"
results <- ET(data, constants, est = "potential", solar = 
"sunshine hours", Tdew = TRUE)

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