| GDH_linear {fruclimadapt} | R Documentation |
Calculates growing degree hours (GDH) using a linear method
Description
The function calculates the daily heat unit accumulation (GDH) from hourly temperature data, using a standard linear model or the linear model proposed by Anderson and Seeley (1992). The standard model is defined by a base temperature, and the Anderson and Seeley (1992) includes also optimum and critical temperatures. In both variants, heat accumulation begins when temperatures are above a minimum (base temperature, Tb), and growth increases linearly with temperature. In the Anderson and Seeley (1992) variant, growth no longer increases once the optimum temperature (Topt) is reached, meaning that GDH above it are constant. The critical temperature (Tcrit) is the temperature above which growth ceases (i.e. GDH=0). The function allows the user to define Tb, Topt and Tcrit, and uses as default the values set by Anderson et al (1986) for fruit trees: Tb=4ºC, Topt=25ºC and Tcrit=36ºC. In the standard linear model with upper thresholds, use Topt = 999 and Tcrit = 999.
Usage
GDH_linear(Hourdata, Tb = 4, Topt = 25, Tcrit = 36)
Arguments
Hourdata |
a dataframe of hourly temperatures. This data frame must have a column for Year, Month, Day, DOY (day of year),Hour, and Temp (hourly temperature). |
Tb |
the base temperatures to calculate GDH |
Topt |
an optional optimal temperatures to calculate GDH |
Tcrit |
an optional critical temperature |
Value
dataframe with daily data. It contains the columns Date, Year, Month, Day, DOY (day of the year), and GDH
Author(s)
Carlos Miranda, carlos.miranda@unavarra.es
References
Anderson JL and Seeley SD, 1992. Modelling strategy in pomology: Development of the Utah models. Acta Horticulturae 313, 297-306.
Examples
# Generate hourly temperatures for the example dataset
library(magrittr)
library(dplyr)
library(lubridate)
Weather <- Tudela_DW %>%
filter (Tudela_DW$Year==2003)
Tudela_HT <- hourly_temps(Weather,42.13132)
# Calculate GDH using default threshold temperatures
GDH_default <- GDH_linear(Tudela_HT)
# Calculate GDH using an optimal temperature threshold with
# no critical threshold
GDH_custom <- GDH_linear(Tudela_HT, 4.5, 22, 999)