wlai {BIOdry}

Walter-Lieth aridity index

Description

Computing the annual aridity index from Walter-Lieth climate diagrams

Usage

wlai(cd, sqt = TRUE)

Arguments

cd

data.frame. Multilevel climatic data series of monthly precipitation sums (mm), and monthly average temperatures (degree C), with row names being monthly characters in month.abb or month.name.

sqt

logical. Print the square root of the aridity index. If TRUE then computed aridity index is normalized with a square root transformation.

Details

Areas between temperature and precipitation lines when precipitation exceeds temperature are calculated as indicators of moist seasons, and areas where temperature exceeds precipitation are calculated as indicator of dry season. The aridity index is defined as the quotient between the areas of dry and wet seasons. Precipitations over 100 mm are scaled such that 1 degree C is equal to 5 mm.

Value

numeric aridity index and plot of the Walter-Lieth diagram.

Author(s)

Wilson Lara <[e-mail]>, Felipe Bravo <[e-mail]>

References

Manrique E., A. Fernandez-Cancio. 2000. Extreme climatic events in dendroclimatic reconstructions from Spain. Clim. Chang., 44: 123-138.

Examples

##random simulation of climatic records
set.seed(1)
pr <- rnorm(12,1,1)
tm <- rnorm(12,0,1)
cld <- data.frame(pr,tm)
##labels of months from october to september
rownames(cld) <- month.abb[c(10:12,1:9)]
rownames(cld) <- c(10:12,1:9)
##computation of the aridity index and climate diagram
AI <- wlai(cld)
AI