The Branas index combines temperature and precipitation during the
growing season to estimate disease pressure (especially downy mildew)
in vineyards. It is the sum of (monthly mean temperature) times
(monthly precipitation total) over the five months of the growing
season: April-August in the Northern Hemisphere; October-February
in the Southern Hemisphere. The Southern Hemisphere season spans
two calendar years and is reported under the year in which it
starts.
Usage
ck_branas(precip, tavg, dates, lat = 50)
Arguments
- precip
Numeric vector of daily precipitation (mm).
- tavg
Numeric vector of daily mean temperatures (degrees C).
- dates
Date vector of the same length as precip.
- lat
Numeric. Latitude in decimal degrees, used to select the
hemisphere convention. Default 50 (Northern Hemisphere).
Value
A data frame with columns period, value, index, and unit.
References
Branas, J., Bernon, G., & Levadoux, L. (1946).
Elements de viticulture generale.
Examples
dates <- seq(as.Date("2024-04-01"), as.Date("2024-08-31"), by = "day")
set.seed(42)
tavg <- rnorm(length(dates), mean = 12, sd = 3)
precip <- rgamma(length(dates), shape = 0.5, rate = 0.2)
ck_branas(precip, tavg, dates)
#> period value index unit
#> 1 2024-01-01 4246.801 branas mm·°C