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Vegetation Start and End Method "ETCCDI"

Source: R/veg_starts.R
method_ETCCDI.Rd

The ETCCDI or StdMeteo method was defined by Expert Team on Climate Change Detection and Indices and is often known as Growing season Length (GSL) and widely used in climate change studies.

Calculation

Implementation of start

first span of at least 6 consecutive days with daily mean temperature TG > 5°C

# mark days warmer than 5°C
df$period <- ifelse(df$Tavg > Tmin, 1, 0)

# find first six day span per year
start <- tapply(df$period, df$year, FUN=function(x){
  sixer <- as.numeric(stats::filter(x, rep(1, 6), sides=1))
  doy <- which(!is.na(sixer) & sixer == 6)
  ifelse(length(doy) == 0, NA, min(doy))
})

Implementation of end

first span after July 1st of 6 consecutive days with TG < 5°C.

# 1. July is DOY 182 and DOY 183 in leap years
years <- unique(df$year)
leap_year <- ifelse((years%%4==0 & years%%100!=0) | years%%400==0, TRUE, FALSE)
jul1 <- ifelse(leap_year, 183L, 182L)

# mark days colder than 5°C
df$period <- ifelse(df$Tavg < Tmin, 1, 0)

# find first six day span per year
end <- ifelse(leap_year, 366L, 365L)
for(i in seq_along(years)){
  temp <- df[df$year == years[i] & df$DOY > jul1[i], ]
  temp$six <-  as.numeric(stats::filter(temp$period, rep(1, 6), sides=1))
  possible.end <- temp[!is.na(temp$six) & temp$six == 6, "DOY"]
  if(length(possible.end) > 0)
    end[i] <- min(possible.end)
}

References

Definition recommended by the CCl/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI) http://etccdi.pacificclimate.org/list_27_indices.shtml http://www.climdex.org/indices.html

European Climate Assessment (ECA) http://eca.knmi.nl/indicesextremes/indicesdictionary.php

ETCCDI (2009) Climate Change Indices: Definitions of the 27 core indices. http://etccdi.pacificclimate.org/list_27_indices.shtml Frich, P., Alexander, L., Della-Marta, P., Gleason, B., Haylock, M., Klein Tank, A. and Peterson, T. (2002) Observed coherent changes in climatic extremes during the second half of the twentieth century. Climate Research, 19, 193–212. https://doi.org/10.3354/cr019193. http://www.climateknowledge.org/heat_waves/Doc2004_Frich_Extremes_Index_ClimResearch_2002.pdf

Zhang, X., Alexander, L., Hegerl, G. C., Jones, P., Tank, A. K., Peterson, T. C., Trewin, B. and Zwiers, F. W. (2011) Indices for monitoring changes in extremes based on daily temperature and precipitation data. Wiley Interdisciplinary Reviews: Climate Change, 2(6), 851–870. https://doi.org/10.1002/wcc.147.