Annual summary of the daily Excess Heat Factor heatwave intensity metric. EHF combines a 3-day mean daily temperature anomaly above the 95th percentile of the reference period with an acclimatisation term (3-day mean minus previous 30-day mean). Positive EHF days indicate heatwave conditions; larger values indicate more severe or less-acclimatised events. This is the operational heatwave metric used by the Australian Bureau of Meteorology.
Usage
ck_ehf(
tmax,
tmin,
dates,
ref_start = 1961L,
ref_end = 1990L,
stat = c("max", "n_positive", "sum_positive")
)Arguments
- tmax
Numeric vector of daily maximum temperatures (degrees C).
- 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.
- stat
One of
"max","n_positive", or"sum_positive".
Details
Three annual summaries are exposed via the stat argument:
"max"(default): peak EHF in the year. Strongest single-day intensity."n_positive": count of days withEHF > 0. A frequency-of-heatwave-conditions measure."sum_positive": sum of EHF on days withEHF > 0. A severity-weighted total.
References
Nairn, J. R., & Fawcett, R. J. B. (2013). Defining heatwaves: heatwave defined as a heat-impact event servicing all community and business sectors in Australia. CAWCR Technical Report No. 060.
Perkins, S. E., & Alexander, L. V. (2013). On the measurement of heatwaves. Journal of Climate, 26(13), 4500-4517. doi:10.1175/JCLI-D-12-00383.1 .
Examples
set.seed(1)
dates <- seq(as.Date("1961-01-01"), as.Date("1991-12-31"), by = "day")
s <- 2 * pi * as.integer(format(dates, "%j")) / 365
tmax <- 20 + 10 * sin(s) + rnorm(length(dates))
tmin <- 10 + 8 * sin(s) + rnorm(length(dates))
tail(ck_ehf(tmax, tmin, dates))
#> period value index unit
#> 26 1986-01-01 3.351686 ehf_max °C^2
#> 27 1987-01-01 3.760517 ehf_max °C^2
#> 28 1988-01-01 3.311125 ehf_max °C^2
#> 29 1989-01-01 3.024947 ehf_max °C^2
#> 30 1990-01-01 3.067609 ehf_max °C^2
#> 31 1991-01-01 3.301835 ehf_max °C^2