Computes daily potential evapotranspiration (PET) from air temperature and
latitude alone, following Oudin et al. (2005). Because it needs no radiation,
humidity or wind data, it suits data-scarce settings where only temperature
is available. Extraterrestrial radiation is derived from solar geometry for
the given day of year and latitude.
Usage
pet_oudin(jday, temp_c, lat_deg)
Arguments
- jday
Integer vector of Julian day of year (1–366).
- temp_c
Numeric vector of mean daily air temperature in degrees
Celsius, the same length as jday.
- lat_deg
Latitude in decimal degrees (positive north, negative south).
Value
A numeric vector of PET in millimetres per day, never negative.
References
Oudin, L. et al. (2005) Which potential evapotranspiration input for a lumped
rainfall-runoff model? Journal of Hydrology 303, 290–306.
doi:10.1016/j.jhydrol.2004.08.026
Examples
# A year of PET for Accra (latitude ~5.6 N)
jd <- 1:365
temp <- 28 + 3 * sin(2 * pi * (jd - 40) / 365)
pet <- pet_oudin(jd, temp, lat_deg = 5.6)
range(pet)
#> [1] 4.115981 5.472362