Warm Spell Days (Series-Quantile Approximation) — ck_warm

Count the number of days in warm spells, where a warm spell is defined as at least six consecutive days with Tmax above the threshold quantile of the full input series. This is a quick approximation driven by a single series-wide quantile, and does not require a reference period.

Usage

ck_warm_spell(tmax, dates, threshold = 0.9, period = "annual")

Arguments

tmax: Numeric vector of daily maximum temperatures (degrees C).
dates: Date vector of the same length as tmax.
threshold: Numeric. Quantile threshold (default 0.9, i.e. 90th percentile).
period: Character. Aggregation period: "annual" (default) or "monthly".

Value

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

Details

For the canonical ETCCDI WSDI definition (1961-1990 calendar-day base, six-day spell rule), use ck_wsdi().

The quantile is estimated with the Hyndman and Fan type 8 estimator, matching every other percentile in climatekit. Before v0.2.1 this function alone used R's default type 7. The two estimators differ by order 1/n, so counts rarely change on multi-year daily series.

Examples

dates <- as.Date("2024-01-01") + 0:364
set.seed(42)
tmax <- rnorm(365, mean = 20, sd = 5)
ck_warm_spell(tmax, dates)
#>       period value      index unit
#> 1 2024-01-01     0 warm_spell days