agroclim (version 0.3.0)

gdd: Growing Degree Days

Description

Growing Degree Day (GDD) or Winkler index. Useful as a zoning tool to differentiate between grape varieties and climate (Winkler et al. 1974).

Usage

gdd(mx, mn, dates, lati = NULL, iniday, endday)

Value

The sum of growing-degree-days is returned as a numeric value.

Arguments

mx

vector of daily maximum temperature series.

mn

vector of daily minimum temperature series.

dates

vector of dates corresponding with daily temprature series

lati

(optional) numeric value indicating the latitude of location.

iniday

initial date in text format ("YYYY-mm-dd"). If "lati" is defined, "iniday" and "endday" are automatically set.

endday

last date in text format ("YYYY-mm-dd"). If "lati" is defined, "iniday" and "endday" are automatically set.

Details

Depending on the latitude, the function detects the hemisphere and considers growing season from 1st April to 31st October (northern hemisphere) or from 1st October to 30rd April (southern hemisphere).

References

Winkler AJ, Cook JA, Kliwer WM, Lider LA (1974) General viticulture. University of California Press, Berkeley, CA

Examples

  gdd(mx = daily_tmax,
    mn = daily_tmin,
    dates = seq.Date(as.Date('1981-01-01'),
            as.Date('2010-12-31'), by ='day'),
            lati = 42)