gdd {pollen}

Growing Degree Days Function

Description

This function calculates growing degree days (GDD) using the average of the daily maximum and minimum temperatures, a base temperature and a maximum base temperature

Usage

gdd(tmax, tmin, tbase, tbase_max, type = "C")

Arguments

tmax

daily maximum temperature

tmin

daily minimum temperature

tbase

base temperature

tbase_max

maximum base temperature

type

either "B", "C", or "D". The default is "C". Type "B" - The heat units are calculated based on the difference between the mean daily temperature and the threshold ('tbase'). In the case when the value of 'tmin' is lower than 'tbase', then it is replaced by 'tbase'. Type '"C"' - same as type '"B"' and when the value of 'tmax' is larger than 'tbase_max', then it is replaced by 'tbase_max'. Type '"D"'- same as type '"B"' and when the value of 'tmax' is larger than 'tbase_max', then no heat units are added.

Value

a numeric vector with GDD values

References

Baskerville, G., & Emin, P. (1969). Rapid Estimation of Heat Accumulation from Maximum and Minimum Temperatures. Ecology, 50(3), 514-517. doi:10.2307/1933912

See Also

[base_temp()] for determining a base temperature

Examples

set.seed(25)
df <- data.frame(tmax = runif(100, 6, 10), tmin = runif(100, 4, 6))

gdd(tmax = df$tmax, tmin = df$tmin, tbase = 5, tbase_max = 30)