R/sucal.R

In sirad: Functions for Calculating Daily Solar Radiation and Evapotranspiration

sucal <-
  function(days,lat,rad_mea,extraT =NULL,tmax,tmin,cc) {
    
    i <- dayOfYear(days)
    latt <- radians(lat)
    if (is.null(extraT)) extraT <-  extrat(lat=latt,i)$ExtraTerrestrialSolarRadiationDaily  # [MJ]
    
    Y <- rad_mea/extraT          
    dtemp <- sqrt(tmax-tmin)  
    cl <- sqrt(1-cc/8)   
    m <- lm(I(Y) ~ dtemp + cl + I(1/extraT) - 1)
    rval <- c(m$coefficients,summary(m)$r.squared)
    names(rval) <- c("Sa","Sb","Sc","Sr2")
    rval
  }