chill_hours function

Calculation of chill hours from hourly temperature data (Weinberger model)

The function calculates chill hours using the Weinberger (1950), or 0-7.2ºC method. Sums chill hours over winter, with one chill hour accumulated for hourly temperatures between 0 and 7.2°C. This is a classic method but highly inefficient, particularly for warm regions and in climate change scenarios, as it disregards temperature ranges that are now known to contribute to the fulfilment of chilling requirements. For that reason, its use is not recommended, it is offered only for educational purposes (i.e. comparison of model performance) and compatibility with older bibliography.

chill_hours(climdata, Start)

Arguments

• climdata: a dataframe with hourly temperature data. It must contain the columns Year, Month, Day, DOY, Hour, Temp.
• Start: parameter indicating the day of the year when chill accumulation is supposed to start.

Returns

dataframe with the chill accumulated for all the seasons in the dataset. Seasons begin at the start date and end the day before the start date of the following year. It contains the columns Year, Month, Day, DOY and Chill.

Examples

# Generate hourly temperatures
library(magrittr)
library(dplyr)
library(lubridate)
Tudela_Sel <- Tudela_DW %>% filter(Tudela_DW$Year<=2002)
Tudela_HT <- hourly_temps(Tudela_Sel,42.13132)
# Calculate chill as chill hours, starting on DOY 305
Chill_h <- chill_hours(Tudela_HT,305)

References

Weinberger JH, 1950. Chilling requirements of peach varieties. Proc Am Soc Hortic Sci 56, 122-128.

Author(s)

Carlos Miranda, carlos.miranda@unavarra.es