Nothing
wDC <- function(DCf = 100, rw = 200, a = 0.75, b = 0.75) {
#############################################################################
# Description:
# Computes the over wintering Drought Code (DC) value.
# All variables names are laid out in the same manner as Lawson & Armitage
# (2008).
# Lawson B.D. and Armitage O.B. 2008. Weather Guide for the Canadian Forest
# Fire Danger Rating System. Natural Resources Canada, Canadian Forest
# Service, Northern Forestry Centre, Edmonton, Alberta. 84 p.
# http://cfs.nrcan.gc.ca/pubwarehouse/pdfs/29152.pdf
#
# Args:
# DCf: Final Fall DC Value
# rw: winter precipitation (mm)
# a: user-selected value accounting for carry-over fraction
# b: user-selected value accounting for wetting efficiency fraction
# Returns:
# DCs: Overwintered Drought Code (Spring startup DC value)
#
#############################################################################
#Eq. 3 - Final fall moisture equivalent of the DC
Qf <- 800 * exp(-DCf / 400)
#Eq. 2 - Starting spring moisture equivalent of the DC
Qs <- a * Qf + b * (3.94 * rw)
#Eq. 4 - Spring start-up value for the DC
DCs <- 400 * log(800 / Qs)
#Constrain DC
DCs <- ifelse(DCs < 15, 15, DCs)
return(DCs)
}
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