I don't know the software mentioned.  I find it unusual on the times.  Usually for each 6 hour period within a day, at 30 minute intervals, 0030-0600, 0630-1200, 1230-1800, 1830-2400 hours.  If younstart with 0000, that reading will include rainfall from the previous day.  If you start with 0030, that is the rain accumulated during the first 30 minutes.  If I had your 30 minute file in excel, it would be no problem accumulating 2, 12, 24, and 48 30 minute reading combinations into 1, 6, 12 and 24 hour composites in separate columns.  Software can be great, but it does not hurt to know what to do so you can check answers.  The daily sum however should be from 0030-2400.  The rain caught from 0000-0030 is reported at 0030 hours.

should work using timeselsum by using the timesteps you want to accumulate:

cdo timeselsum,11 file.nc outfile.nc

Thank you all for your useful suggestions. I finally used CDO and the following two lines of code:

cdo timselsum,12 mergedfiles_withTime.nc4 sixhourSum.nc4

CDO_TIMESTAT_DATE=last cdo -f nc4 -z zip9 -shifttime,-45min -shifttime,-2hour sixhourSum.nc4 sixhourSumFinal.nc4

Hope this helps someone in need of a solution. Our paper is now online at http://journals.ametsoc.org/doi/abs/10.1175/JHM-D-16-0187.1

You can use daysum from CDO as:

cdo daysum foo_hourly.nc foo_daily_sum.nc

Also, there are daily aggreggators:

cdo daymean foo_hourly.nc foo_daily_mean.nc

cdo daymin foo_hourly.nc foo_daily_min.nc

cdo daymax foo_hourly.nc foo_daily_max.nc

Dears,

I have similar problem to sum " accumulated precipitation from 00:00 to 12:00 (time 00:00 + step 12)" + " accumulated precipitation from 12:00 to 24:00 (time 12:00 + step 12) " to get the daily total precipitation.

I've attached the data file. I'll be thankful if I have your help.

Sincerely

Zilefac Elvis Asong I also want to calculate sum 6h rainfall from hourly data starting from 00UTC to 23UTC. I applied "cdo timselsum,6 ifile ofile"; but it seemed to be wrong since the time step of the ofile showed 02:30 - 08:30 - 14:30 - 20:30. Besides, when I displayed the final steps by grads, it presented undefined values. Do you have any idea about this problems? Can I apply the code you suggested to get the accumulated 6 hour precipitation? Thank you so much.

Hi Hoa,

you may try to set the noffset and nskip to zeros:

"cdo -O -f nc4c -z zip -L -timselsum,6,0,0 infile outfile"

Hoa Thi Thanh Pham I think the issue is with the timestamp after applying ' cdo timselsum,6 ifile ofile'. The values should be correct. In which case you can shift the time backwards by making necessary changes in this line of code:

cdo -f nc4 -z zip9 -shifttime,-45min -shifttime,-2hour ifile outfile

Or you can use noffset , nskip as Mohanad Zaghloul indicated above.

hope this helps.

Cheers

Elvis

Mohanad Zaghloul Zilefac Elvis Asong Thank you so much for your valuable feedbacks. Your both codes worked fine with my initial file. The problem appeared when I shifted the time 12 hours backward since I tried to fix the time of this data with the observation data which started from 12 UTC.

Could you please teach me how to do this in R? Many thanks!

cdo daysum IN OUT

cdo timselsum,11,0,1 input output