Growing degree days

Daily thermal time by the capped-average method: the mean of the daily maximum and minimum, each first constrained to the interval between the base and upper temperatures, less the base temperature, with negative values set to zero.

Usage

growing_degree_days(tmin, tmax, t_base = 5, t_upper = Inf)

Arguments

tmin, tmax

Numeric vectors of daily minimum and maximum temperature in degrees Celsius.

t_base

Base temperature below which development is taken to stop.

t_upper

Temperature above which further warmth adds no development.

Value

A numeric vector of daily growing degree days, never negative.

Details

This is the interpretation McMaster and Wilhelm (1997) label Method 1 with a horizontal cut-off. The choice matters: the two common interpretations of the same equation can differ by hundreds of degree days over a season, so the method is stated rather than left implicit.

References

McMaster, G. S. & Wilhelm, W. W. (1997) "Growing degree-days: one equation, two interpretations." Agricultural and Forest Meteorology 87, 291-300. doi:10.1016/S0168-1923(97)00027-0

See also

crop_parameters(), phenology_windows()

Examples

growing_degree_days(tmin = c(4, 8, 12), tmax = c(18, 24, 33), t_base = 5)
#> [1]  6.5 11.0 17.5