medfate (version 0.7.4)

hydrology.rainInterception: Rainfall interception

Description

Function hydrology.rainInterception calculates the amount of rainfall intercepted daily by the canopy, given a rainfall and canopy characteristics. Two canopy interception models are currently available: the sparse Gash (1995) model and the Liu (2001) model. In both cases the current implementation assumes no trunk interception.

Usage

hydrology.rainInterception(Rainfall, Cm, p, ER=0.05, method="Gash1995")

Arguments

Rainfall

A numeric vector of (daily) rainfall.

Cm

Canopy water storage capacity.

p

Proportion of throughfall (normally 1 - c, where c is the canopy cover).

ER

The ratio of evaporation rate to rainfall rate.

method

Rainfall interception method (either "Gash1995" or Liu2001).

Value

Returns a vector of the same length as Rainfall containing intercepted rain values.

Details

The function is prepared to accept both vectors or scalars for parameters Cm, p and ER. If they are supplied as vectors they should be of the same length as Rainfall.

References

Liu (2001). Evaluation of the Liu model for predicting rainfall interception in forests world-wide. - Hydrol. Process. 15: 2341-2360.

Gash (1979). An analytical model of rainfall interception by forests. - Quarterly Journal of the Royal Meteorological Society

Gash et al. (1995). Estimating sparse forest rainfall interception with an analytical model. - Journal of Hydrology

See Also

spwb

Examples

# NOT RUN {
throughfallMatrixGash<-function(P = seq(1,50, by=1), Cm = seq(1,5, by=1), 
                                ER = 0.08,p=0.8) {
  m2<- P - hydrology.rainInterception(P,Cm[1],p,ER=ER)
  for(i in 2:length(Cm)) {
    m2<-rbind(m2,P-hydrology.rainInterception(P,Cm[i],p,ER=ER))
  }
  colnames(m2)<-P
  rownames(m2)<-Cm
  return(m2)
}

Cm = c(0.5,seq(1,4, by=1))
P = seq(1,50, by=1)

m2 = throughfallMatrixGash(P=P, p=0.2, Cm=Cm,ER = 0.05)
rt = sweep(m2,2,P,"/")*100
matplot(t(rt), type="l", axes=TRUE, ylab="Relative throughfall (%)", 
        xlab="Gross rainfall (mm)", xlim=c(0,length(P)), 
        lty=1:length(Cm), col="black", ylim=c(0,100))
title(main="p = 0.2 E/R = 0.05")
legend("bottomright",lty=1:length(Cm), legend=paste("Cm =",Cm), bty="n")

# }