ck_cwn: Cold-Wave Number (CWN)
In climatekit: Unified Climate Indices for Temperature, Precipitation, and Drought

ck_cwn

R Documentation

Cold-Wave Number (CWN)

Description

ET-SCI cold-wave family index. Annual count of distinct cold-wave events, where a cold wave is a span of at least three consecutive days with daily Tmin below the 10th percentile of the calendar-day distribution from a reference period (default 1961 to 1990).

Usage

ck_cwn(tmin, dates, ref_start = 1961L, ref_end = 1990L, min_spell = 3L)

Arguments

`tmin`	Numeric vector of daily minimum temperatures (degrees C).
`dates`	Date vector of the same length as `tmax`. Must contain data covering the reference period.
`ref_start`, `ref_end`	Integer. Reference period boundary years (inclusive). Defaults to 1961 and 1990.
`min_spell`	Integer. Minimum spell length in days (default 3, the ET-SCI standard).

Value

A data frame with columns period, value, index, and unit.

Examples

set.seed(1)
dates <- seq(as.Date("1961-01-01"), as.Date("1991-12-31"), by = "day")
tmin <- 5 + 8 * sin(2 * pi * as.integer(format(dates, "%j")) / 365) +
        rnorm(length(dates))
tail(ck_cwn(tmin, dates))

climatekit documentation built on May 9, 2026, 5:08 p.m.