CDO

Hi Syed!

Here is an example usage of trend: suppose you have temperature evolution like this:

I created it with

cdo -f nc -settaxis,2001-01-01,12:00:00,1days -expr,'Temp=25*sin(seq*3.141529/360)+seq/100' -seq,1,10000

if you want to do a computation of the trend on a decade, you have to select each decade separately and to the trend calculation I guess

cheers
ralf

thanks for the explanation ralf. what number does "equal" represents in this cdo trend[,equal] infile outfile1 outfile2 ?

it's not a number, but a boolean - must be set 'true' or 'false'

what is the affect on output by setting it true or false?

it has to do with the time-axis. Normally the operators expects an equally spaced time-axis. with 'false' given, it can be unequally spaced, like years and months. this triggers another trend-algorithm.

cheers
ralf

@ ralf
how would be the trend calculated if we want to do it for a variable like seal level pressure for a month lets say july over a time period of 1980-2016...check the attached file for consideration also.

the trend operator is on only useful for time-series data. your input is horizontally distributed - so it doesn't work in that case

@Ralf Thehos Mueller

What if i choose single level for the said variable (as this variable is already single level 1000hPa). while time is already mentioned (july month since 1980-2016). then?

you have to select a single horizontal location or reduce this dimension in any other way (maybe a horizontal mean is suitable, too). I cannot say what is useful for you

can you check these files. they are vertically reduced to single level..

your files have only a single timestep - that's nothing I could create a time-series from, sorry.

cheers
ralf