tempResponse_hourtable function

Add metric accumulation to table of hourly temperatures

This function calculates cumulative values for temperature response metrics for every hour of an hourly temperature record. The count is restarted on a specified date each year. The function is a generalized version of chilling_hourtable, which only worked with three predefined chilling one predefined heat metrics.

tempResponse_hourtable(
  hourtemps,
  Start_JDay,
  models = c(Chill_Portions = Dynamic_Model, GDH = GDH_model)
)

Arguments

• hourtemps: a dataframe of stacked hourly temperatures (e.g. produced by stack_hourly_temps). This data frame must have a column for Year, a column for JDay (Julian date, or day of the year), a column for Hour and a column for Temp (hourly temperature).
• Start_JDay: the start date (in Julian date, or day of the year) of the calculation for the four metrics. The count is restarted on this date every year.
• models: named list of models that should be applied to the hourly temperature data. These should be functions that take as input a vector of hourly temperatures. This defaults to c(Chill_Portions = Dynamic_Model, GDH = GDH_model), which refer to the Dynamic chill model and the Growing Degree Hours model functions contained in chillR.

Returns

data frame consisting of all the columns of the THourly input data frame, plus one additional column for each model, which contains the cumulative number of model metrics since the last Start_JDay).

Note

After doing extensive model comparisons, and reviewing a lot of relevant literature, I do not recommend using the Chilling Hours or Utah Models, especially in warm climates! The Dynamic Model (Chill Portions), though far from perfect, seems much more reliable.

Examples

weather<-fix_weather(KA_weather[which(KA_weather$Year>2008),])

hourtemps<-stack_hourly_temps(weather,latitude=50.4)

cht<-chilling_hourtable(hourtemps,20)

References

Model references:

Dynamic Model:

Erez A, Fishman S, Linsley-Noakes GC, Allan P (1990) The dynamic model for rest completion in peach buds. Acta Hortic 276, 165-174

Fishman S, Erez A, Couvillon GA (1987a) The temperature dependence of dormancy breaking in plants - computer simulation of processes studied under controlled temperatures. J Theor Biol 126(3), 309-321

Fishman S, Erez A, Couvillon GA (1987b) The temperature dependence of dormancy breaking in plants - mathematical analysis of a two-step model involving a cooperative transition. J Theor Biol 124(4), 473-483

Growing Degree Hours:

Anderson JL, Richardson EA, Kesner CD (1986) Validation of chill unit and flower bud phenology models for 'Montmorency' sour cherry. Acta Hortic 184, 71-78

Review on chilling models in a climate change context:

Luedeling E, 2012. Climate change impacts on winter chill for temperate fruit and nut production: a review. Scientia Horticulturae 144, 218-229

Author(s)

Eike Luedeling