fruclimadapt (version 0.4.5)

GDD_linear: Calculates growing degree days (GDD) using a linear method

Description

The function calculates the daily heat unit accumulation (GDD) from daily temperature data with a linear method based on averaging the daily maximum and minimum temperatures (Arnold, 1960). GDD are calculated by subtracting the plant's lower base temperature (Tb) from the average daily air temperature. The user can define an upper temperature threshold (Tu) so that all temperatures above Tu will have equal value in GDD summation.

Usage

GDD_linear(Temp_Day, Tb, Tu = 999)

Value

dataframe consisting of the columns Year, Month, Day, Tmax, Tmin, Tmean and GDD.

Arguments

Temp_Day

a dataframe of daily temperatures. This data frame must have a column for Year, Month, Day, and daily minimum (Tmin) and maximum (Tmax) temperatures.

Tb

the base temperature required to calculate GDD.

Tu

an optional upper temperature threshold.

Author

Carlos Miranda,

References

Arnold, C.Y. 1960. Maximum-minimum temperatures as a basis for computing heat units. Proc.Amer. Soc. Hort. Sci. 76:682–692.

Examples

# Calculate GDD in the example dataset using 4.5ºC as base temperature and no 
# upper threshold.
library(magrittr)
library(dplyr)
GDD <- GDD_linear(Tudela_DW,4.5)
# Calculate GDD in the example dataset using 4.5ºC as base temperature and an 
# upper threshold at 25ºC.
GDD <- GDD_linear(Tudela_DW,4.5,25)