AET = P + PET - (P^w + PET^w)^(1/w): Fu's (1981) form of the Budyko
curve, as given by Zhang et al. (2004, Water Resources Research 40,
W02502). It is 0 when either P or PET is 0, tends to PET where water is
plentiful and to P where it is scarce, and never exceeds either. omega sets
how closely it hugs those limits; 2.6 is the mean Zhang et al. fitted over
470 catchments.
Usage
wet_aet_budyko(p, pet, omega = 2.6)
Arguments
- p, pet
Long-term mean annual precipitation and potential (reference)
evapotranspiration (mm): numeric vectors or SpatRasters. Negative values
count as 0.
- omega
Fu's parameter, greater than 1.
Value
Actual evapotranspiration (mm), like the inputs.
Details
Applied per cell to long-term annual means, it gives the evaporation that
the local demand and supply imply, whatever a soil-bucket product computed
from a different precipitation.
Examples
# Greata Creek (Okanagan): P 746 mm against a demand of about 650 mm
wet_aet_budyko(746, 650)
#> [1] 481.3161
# the whole curve, as the evaporative index E/P against the dryness index PET/P
dryness <- c(0.25, 0.5, 1, 2, 4)
round(wet_aet_budyko(1, dryness), 2)
#> [1] 0.24 0.44 0.69 0.88 0.96
