TotalSpellTimeExceedingThreshold: Total Spell Time Exceeding Threshold

Description

The number of days (when daily data is provided) that are part of a spell (defined by its minimum length e.g. 6 consecutive days) that exceed (or not exceed) a threshold are calculated with TotalSpellTimeExceedingThreshold. This function allows to compute indicators widely used in Climate Services, such as:

'WSDI', Warm Spell Duration Index that count the total number of days with at least 6 consecutive days when the daily temperature maximum exceeds its 90th percentile.

This function requires the data and the threshold to be in the same units. The 90th percentile can be translate into absolute values given a reference dataset using function Threshold or the data can be transform into probabilites by using function AbsToProbs. See section @examples.

Usage

TotalSpellTimeExceedingThreshold(
  data,
  threshold,
  spell,
  op = ">",
  dates = NULL,
  start = NULL,
  end = NULL,
  time_dim = "time",
  ncores = NULL
)

Value

A multidimensional array with named dimensions containing the number of days that are part of a spell within a threshold with dimensions of the input parameter 'data' except the dimension where the indicator has been computed.

Arguments

data: A multidimensional array with named dimensions.
threshold: If only one threshold is used: it can be a multidimensional array with named dimensions. It must be in the same units and with the common dimensions of the same length as parameter 'data'. It can also be a vector with the same length of 'time_dim' from 'data' or a scalar. If we want to use two thresholds: it can be a vector of two scalars, a list of two vectors with the same length of 'time_dim' from 'data' or a list of two multidimensional arrays with the common dimensions of the same length as parameter 'data'. If two thresholds are used, parameter 'op' must be also a vector of two elements.
spell: A scalar indicating the minimum length of the spell.
op: An operator '>' (by default), '<', '>=' or '<='. If two thresholds are used it has to be a vector of a pair of two logical operators: c('<', '>'), c('<', '>='), c('<=', '>'), c('<=', '>='), c('>', '<'), c('>', '<='), c('>=', '<'),c('>=', '<=')).
dates: A multidimensional array of dates with named dimensions matching the temporal dimensions on parameter 'data'. By default it is NULL, to select aperiod this parameter must be provided.
start: An optional parameter to defined the initial date of the period to select from the data by providing a list of two elements: the initial date of the period and the initial month of the period. By default it is set to NULL and the indicator is computed using all the data provided in data.
end: An optional parameter to define the final date of the period to select from the data by providing a list of two elements: the final day of the period and the final month of the period. By default it is set to NULL and the indicator is computed using all the data provided in data.
time_dim: A character string indicating the name of the dimension to compute the indicator. By default, it is set to 'time'. It can only indicate one time dimension.
ncores: An integer indicating the number of cores to use in parallel computation.

Details

This function considers NA values as the end of the spell. For a different behaviour consider to modify the 'data' input by substituting NA values by values exceeding the threshold.

Examples

Run this code

data <- array(1:100, c(member = 5, sdate = 3, time = 214, lon = 2))
Dates <- c(seq(as.Date("01-05-2000", format = "%d-%m-%Y"), 
              as.Date("30-11-2000", format = "%d-%m-%Y"), by = 'day'),
          seq(as.Date("01-05-2001", format = "%d-%m-%Y"), 
              as.Date("30-11-2001", format = "%d-%m-%Y"), by = 'day'),
          seq(as.Date("01-05-2002", format = "%d-%m-%Y"), 
              as.Date("30-11-2002", format = "%d-%m-%Y"), by = 'day'))
dim(Dates) <- c(sdate = 3, time = 214)

threshold <- array(1:4, c(lat = 4))
total <- TotalSpellTimeExceedingThreshold(data, threshold, dates = Dates, 
                                         spell = 6, start = list(21, 4), 
                                         end = list(21, 6))