continuity_ratio function

Calculates the continuity ratio of a set of precipitation measured or generated data in several sites as defined by Wilks, 1998 (see reference link)

continuity_ratio(data, lag = 0, valmin = 0.5)

Arguments

• data: containing daily precipitation time series for several gauges (one gauge time series per column)
• lag: numeric lag (expressed as number of days) used for computation for "cross" continuity ratio and joint probability of prercipitation (no)occurrence.
• valmin: threshold precipitation value [mm] for wet/dry day indicator. If precipitation is lower than valmin, day is considered dry. Default is 0.5 mm.

Returns

A list containing the following matrices:

continuity_ratio : lag-day lagged continuity ratio ,

occurrence : joint probability of lag-day lagged precipitation occurrence

nooccurrence : joint probability of lag-day lagged no precipitation occurrence.

nooccurrence_occurrence : joint probability of lag-day lagged no precipitation and precipitation occurrence respectively.

occurrence_nooccurrence : joint probability of lag-day lagged precipitation and no precipitation occurrence respectively.

probability_continuity_ratio: lag-day lagged ratio about precipitation probability contitioned to no precipitation/preciitation occurrence in the other site

Note

If lag==0 the function returns the continuity ratio and joint probability as described by Wilks, 1998. Otherwise the precipitation values for each couple of rain gauges are taken with lag-day lag.

Examples

data(trentino)

year_min <- 1961
year_max <- 1990
origin <- paste(year_min,1,1,sep="-")

period <- PRECIPITATION$year>=year_min & PRECIPITATION$year<=year_max
station <- names(PRECIPITATION)[!(names(PRECIPITATION) %in% c("day","month","year"))]
prec_mes <- PRECIPITATION[period,station]  

## removing nonworking stations (e.g. time series with NA)
accepted <- array(TRUE,length(names(prec_mes)))
names(accepted) <- names(prec_mes)
for (it in names(prec_mes)) {
                 accepted[it]  <- (length(which(!is.na(prec_mes[,it])))==length(prec_mes[,it]))
}

prec_mes <- prec_mes[,accepted]
## the dateset is reduced!!! 
prec_mes <- prec_mes[,1:2]

continuity_ratio <-continuity_ratio(data=prec_mes,lag=0,valmin=0.5)
continuity_ratio1 <-continuity_ratio(data=prec_mes,lag=-1,valmin=0.5)

References

see the following URL references: http://onlinelibrary.wiley.com/doi/10.1002/joc.2305/abstract

and http://www.sciencedirect.com/science/article/pii/S0022169498001863