Growing Degree Days and Thermal Indices — thermal

Usage

thermal_indices(
  tmax,
  tmin,
  base_temp = 10,
  sunshine_hours = NULL,
  day_length = NULL,
  crop_yield = NULL,
  biomass = NULL,
  verbose = TRUE,
  upper_temp = NULL,
  method = c("average", "modified")
)

Arguments

tmax: Daily maximum temperature (degrees C).
tmin: Daily minimum temperature (degrees C).
base_temp: Base temperature (degrees C). Default 10.
sunshine_hours: Daily bright sunshine hours (optional, for HTU).
day_length: Daily day length in hours (optional, for PTU); see day_length.
crop_yield: Economic yield (kg/ha) for HUE (optional).
biomass: Total biomass (kg/ha) for HUE (optional).
verbose: Logical. If TRUE (default), prints the results.
upper_temp: Optional upper threshold temperature (degrees C) above which development does not increase.
method: "average" (default): GDD = max(0, (Tmax + Tmin)/2 - Tbase), with the mean capped at upper_temp. "modified": Tmax and Tmin are each limited to the range from base_temp to upper_temp before averaging (McMaster and Wilhelm, 1997, method 2).

Value

An object of class aridagri_thermal: a list with summary (index, value, unit), gdd_total and daily (daily and cumulative GDD, HTU and PTU).

Details

HTU = sum of GDD x bright sunshine hours; PTU = sum of GDD x day length (Rajput, 1980). HUE = yield / GDD (kg/ha per degree-day); HTUE = yield / HTU.

References

McMaster, G.S. and Wilhelm, W.W. (1997). Growing degree-days: one equation, two interpretations. Agricultural and Forest Meteorology, 87(4), 291-300. doi:10.1016/S0168-1923(97)00027-0

Rajput, R.P. (1980). Response of soybean crop to climatic and soil environments. PhD thesis, IARI, New Delhi.

Author

Lalit Kumar Rolaniya, Ram Lal Jat, Monika Punia, Raja Ram Choudhary, Hemant Poonia

Examples

tmax <- c(31, 33, 35, 36, 38, 40, 41, 39, 37, 36)
tmin <- c(16, 17, 19, 20, 22, 24, 25, 24, 22, 21)
thermal_indices(tmax, tmin, base_temp = 10, upper_temp = 40,
                sunshine_hours = rep(9.5, 10),
                day_length = day_length(28, 70:79), crop_yield = 1250)
#> 
#> ======================================================================
#>  THERMAL INDICES
#> ======================================================================
#>  Days = 10   Base temperature = 10.0 C   Upper = 40.0 C   Mean Tmax = 36.6 C   Mean Tmin = 21.0 C
#> 
#>  Index                                Value    Unit                       
#>  Growing degree days (GDD)             188.000 degree C day               
#>  Mean daily GDD                         18.800 degree C day per day       
#>  Helio-thermal units (HTU)            1786.000 degree C day hour          
#>  Photo-thermal units (PTU)            2224.127 degree C day hour          
#>  Heat use efficiency (grain)             6.649 kg/ha per degree C day     
#>  Helio-thermal use efficiency (grain)    0.700 kg/ha per degree C day hour