Potential Evapotranspiration (Hargreaves Method)

Estimate daily PET using the Hargreaves-Samani equation, which requires only daily temperature extremes and latitude.

Usage

ck_pet(tmin, tmax, lat, dates)

Arguments

tmin

Numeric vector of daily minimum temperatures (degrees C).

tmax

Numeric vector of daily maximum temperatures (degrees C).

lat

Numeric. Latitude in decimal degrees.

dates

Date vector of the same length as tmin.

Value

A data frame with columns date, value, index, and unit.

References

Hargreaves, G. H., & Samani, Z. A. (1985). Reference crop evapotranspiration from temperature. Applied Engineering in Agriculture, 1(2), 96-99.

Examples

dates <- as.Date("2024-07-01") + 0:9
tmin <- c(15, 16, 14, 17, 15, 13, 16, 14, 15, 16)
tmax <- c(30, 32, 28, 33, 31, 27, 34, 29, 30, 32)
ck_pet(tmin, tmax, lat = 45, dates = dates)
#>          date    value index unit
#> 1  2024-07-01 6.096361   pet   mm
#> 2  2024-07-02 6.522357   pet   mm
#> 3  2024-07-03 5.655463   pet   mm
#> 4  2024-07-04 6.659415   pet   mm
#> 5  2024-07-05 6.338231   pet   mm
#> 6  2024-07-06 5.483717   pet   mm
#> 7  2024-07-07 7.027908   pet   mm
#> 8  2024-07-08 5.879855   pet   mm
#> 9  2024-07-09 6.017510   pet   mm
#> 10 2024-07-10 6.432733   pet   mm