CDO

Hi Dino,

from the user 'Climate indices with CDO' documentation (https://code.mpimet.mpg.de/projects/cdo/embedded/cdo_eca.pdf):
eca_hwfi - Warm spell days index w.r.t. 90th percentile of reference period (default 6days)

infile=air_temperature_climate-projections-8km-over-italy_historical_318269.nc

cdo -timpctl,90 $infile -timselmin,5 $infile -timselmax,5 $infile tas_90pctl.nc

#-- to get rid of the error:  cdo    eca_hwfi (Abort): Input streams have different time values!
cdo -add tas_90pctl.nc -sub $infile $infile tas_90pctl_with_timesteps.nc

cdo eca_hwfi $infile tas_90pctl_with_timesteps.nc outfile.nc

Thank you very much Dr Meier-Fleischer.
The solution seems to work, however, I'm not sure that it produces what I need.
As the final product, I need a raster with the number of consecutive days above the 90th percentile.
I've tried to run your script for just one year (1979) and for the spring period (months 4-6).

cdo selmonth,4/6 air_temperature_climate-projections-8km-over-italy_historical_308464.nc spring.nc

infile=spring.nc

I've calculated the 90 percentile considering all years as you suggested.
cdo -timpctl,90 $infile -timselmin,5 $infile -timselmax,5 $infile tas_90pctl.nc
cdo -add tas_90pctl.nc -sub $infile $infile tas_90pctl_with_timesteps_spring.nc

Then I calculated the index just for the year 1998
cdo eca_hwfi -selyear,1998 $infile -selyear,1998 tas_90pctl_with_timesteps_spring.nc eca_hwfi_spring_1998.nc

tas_90pctl_with_timesteps_spring is above > 146 MB so here's a google drive link: https://drive.google.com/file/d/1tqBFUrXEibxC9tQx1cU-20gawWA79243/view?usp=sharing

The two variables that I get are:

1. Warm spell day index, ranging from 20 to 90
2. Warm spell periods per period, ranging from 1 to 4.

I'm perplexed about two things:
1. How can this index range from 10 to 80? This year there were up to 80 consecutive days above the 90th percentile? It seems absurd.
2. Also up to 5 warm spells in just 3 months seems a bit off.

I need to produce a final raster with the number of consecutive days > tas_90pctl averaged across the years 1979-2000. Is what am doing really producing what I need?

Thank you very much for your precious assistance.
Dino

Sorry if I come back at you again, I'm stuck on this issue. Could you please provide me with some guidance? Thanks.

Hi Dino,

here is another try using the more complex etccdi index. Note that usually the daily maximum temperature should be used for this index.

1. Calculate a running min and max :

cdo ydrunmin,5,rm=c $tasmax $tasmaxrunmin
cdo ydrunmax,5,rm=c $tasmax $tasmaxrunmax

you take 5 days into account and `rm=c` means that the last time steps are extending the 5 days for the first time steps of the time series as well as that the first time steps are extending the 5 days of the last time steps.

2. You then calculate the 90th percentile with a specific percentile method (r8) by using:

cdo ydrunpctl,90,5,pm=r8,rm=c $tasmax ${tasmaxrunmin} ${tasmaxrunmax} ${tx90thresh}

Note that cdo creates a histogram for calculating the percentile. If you do not have enough memory, the histogram is created by evenly divide the interval between tasmaxrunmin and tasmaxrunmax into iso-size bins. If you have enough memory to store all values of the entire grid in memory to create sorted histograms, you can set:
export CDO_PCTL_NBINS=$((5*(endyear-startyear+1)*2+2))
This means you need to hold 2 * 5 (window size) * the time series in memory (+2 to be sure) for each grid cell. In this case, tasmaxrunmin and tasmaxrunmax are not really needed for calculation.

3. Afterwards, you calculate the wsdi with:

cdo etccdi_wsdi $tasmax $tx90thresh $cdoWsdi

I hope you have better results with this approach.

Best,
Fabi

Hello Fabi,

I'm interested in calculating the WSDI for only the April to July (summer) months. I have data from 01-01-1980 until 31-12-2022. I'm including all the steps that I followed:

cdo selmonth,4,5,6,7 tmax.nc tmax_summer.nc

cdo ydrunmin,5,rm=c tmax_summer.nc tmax_summer_runmin.nc

cdo ydrunmax,5,rm=c tmax_summer.nc tmax_summer_runmax.nc

cdo ydrunpctl,90,5,pm=r8,rm=c tmax_summer.nc tmax_summer_runmin.nc tmax_summer_runmax.nc tx90thresh.nc

cdo etccdi_wsdi tmax_summer.nc tx90thresh.nc wsdi.nc

I followed exactly the steps you mentioned to calculate WSDI; however, when I did CDO SHOWDATE tx90thresh.nc, I found that the dates are from 01-04-2022 until 29-07-2022. However, the last two dates are from 30-07-2021 and 31-07-2021, which are from 2021. Could you tell me why this happened or if I am doing something wrong?