It calculates dry/wet spell duration.

dw.spell(
  data,
  valmin = 0.5,
  origin = "1961-1-1",
  extract = NULL,
  month = 1:12,
  melting.df = FALSE,
  from.start = FALSE,
  only.inner = FALSE
)

Arguments

data: data frame R object containing daily precipitation time series for several gauges (one gauge time series per column).
valmin: threshold precipitation value [mm] for wet/dry day indicator.
origin: character string "yyyy-mm-dd" indicated the date of the first row of "data".
extract: string character referred to the state to be extracted, eg. "dry" or "wet"
month: integer vectors containing the considered months. Default is 1:12 (all the year).
melting.df: logical value. If it TRUE the output is melted into a data frame. Default is FALSE.
from.start: logical value. If is TRUE the spell is referenced to its first day, if it is FALSE (default) the spell is referenced to its last date.
only.inner: logical value. It is used in case extract is not NULL, if the value is TRUE, it extracts dry/wet spells completely inside the selected month period. Default is FALSE.

Value

Function returns a list of data frames containing the spell length expressed in days

Examples

 


data(trentino)

year_min <- 1961
year_max <- 1990

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[,1:3]

origin <- paste(year_min,1,1,sep="-")
dw_spell <- dw.spell(prec_mes,origin=origin)
dw_spell_dry <- dw.spell(prec_mes,origin=origin,extract="dry")

hist(dw_spell_dry$T0001$spell_length)



## Single Gauging Station

prec_mes <- prec_mes[,1]

origin <- paste(year_min,1,1,sep="-")
dw_spell <- dw.spell(prec_mes,origin=origin)
dw_spell_dry <- dw.spell(prec_mes,origin=origin,extract="dry")
dw_spell_dry_start <- dw.spell(prec_mes,origin=origin,extract="dry",
  month=5:8,from.start=TRUE) ## dry spell 
dw_spell_dry_start_2 <- dw.spell(prec_mes,origin=origin,extract="dry",
month=5:8,from.start=TRUE,only.inner=TRUE) ## dry spell 
## is referenced to the first day instead of the latest one as default. 

hist(dw_spell_dry[[1]]$spell_length)