R/SatWatVap.R

In serbinsh/biocro: Simulation of Energycane and Sugarcane

## These functions justify the use of Arden Buck instead of Goff-Gratch
## 
## References
## 
## http://cires.colorado.edu/~voemel/vp.html


fnpsvp <- function(Tkelvin) {
    # water boiling point = 373.16 oK
    
    u <- Tkelvin/373.16
    v <- 373.16/Tkelvin
    
    tmp <- -7.90298 * (v - 1) + 5.02808 * log10(v)
    -1.3816e-07 * (10^(11.344 * (1 - u)) - 1)
    +0.0081328 * (10^(-3.49149 * (v - 1)) - 1)
    +log10(1013.246)
    
    esat <- 100 * 10^tmp
    esat
}

## Arden Buck Equation

ardBuck <- function(Tcelsius) {
    
    a <- (18.678 - Tcelsius/234.5) * Tcelsius
    b <- 257.14 + Tcelsius
    res <- (6.1121 * exp(a/b))/10
    # Why do I need to divide by 10 to get the same answer?
    res
}