R/FMCcalc.r

In fwi.fbp: Fire Weather Index System and Fire Behaviour Prediction System Calculations

  .FMCcalc<-function(LAT,LONG,ELV,DJ,D0){                                                                                               # if D0, date of min FMC, is not known then D0 = NULL.
      FMC  <- rep(-1,length(LAT))
      LATN <- rep(0,length(LAT))   
      LATN <- ifelse(D0<=0,ifelse(ELV<=0,46+23.4*exp(-0.0360*(150-LONG)),43+33.7*exp(-0.0351*(150-LONG))),LATN) #eqs (1)/(3)
      D0   <- ifelse(D0<=0,ifelse(ELV<=0,151*(LAT/LATN),142.1*(LAT/LATN)+0.0172*ELV),D0) #eqs(2)/(4)
      
      D0 <- round(D0,0) #need to round D0 to the nearest integer it is a date, not a partial date
      ND   <- abs(DJ-D0) #eq (5)
      FMC  <- ifelse(ND<30,85+0.0189*ND^2,ifelse(ND>=30&ND<50,32.9+3.17*ND-0.0288*ND^2,120)) #eqs(6)/(7)/(8)
  FMC}