First of al you need to extract daily total precipitation. On the ECMWF data server you can select as start times 00:00 (midnight) and 12:00 (midday), both with step 12. This gives you two records:

* accumulated precipitation from 00:00 to 12:00 (midnight + 12 hours)

* accumulated precipitation from 12:00 to 24:00 (midday + 12 hours)

Then sum the two values to get the daily total.

Further, the unit is m. To get mm you need to multiply by 1000. The cdo command would be 'cdo -r -b 32 mulc,1000 ifile ofile'. Finally you can sum the daily values to get monthly sums.

Hi Majid Kazemzadeh,

If what you want is to calculate the cumulative value of precipitation over a given month in a netCDF file you can use the function  'momsum' (monthly sum) of the CDO operators (https://code.zmaw.de/projects/cdo). See section 2.8.20. MONSTAT - Monthly statistical values.

Hope it helps.

Augusto

Hi there,

convert meter to mm/day by multiplying the whole data with (1000*24/step), For e.g. if the time step is 12, multiply 2000 to get mm/day. To convert the data from mm/day to mm/month you have to aggregate in CDO or R. I aggregate in R using 'zoo-package'. 

>data.new

Hi Majid,

be aware that precipitation in ECMWF products is provided as accumulation from the beginning of the forecast (see: http://www.ecmwf.int/en/faq/what-accumulation-period-era-40). Best would be to check this issue for your specific dataset. Not sure if e.g. cdo routines account for this issue.

Cheers,

Klemens

I think that depends on the units (chek metadata of your files). If precipitation is given as flux (kg/m2/s) the method of calculation would be to calculate the mean flux and multiply by the number of seconds of the given month. An example for january using cdo would be:

cdo mulc,2678400 -timmean fileprec fileout

the result is given in mm

Best regards

First of al you need to extract daily total precipitation. On the ECMWF data server you can select as start times 00:00 (midnight) and 12:00 (midday), both with step 12. This gives you two records:

* accumulated precipitation from 00:00 to 12:00 (midnight + 12 hours)

* accumulated precipitation from 12:00 to 24:00 (midday + 12 hours)

Then sum the two values to get the daily total.

Further, the unit is m. To get mm you need to multiply by 1000. The cdo command would be 'cdo -r -b 32 mulc,1000 ifile ofile'. Finally you can sum the daily values to get monthly sums.

multiplayer the value of precipitation by the time of (days x hours x min. x sec) .

I think what Jitendra Kumar Meher suggested is correct. I am getting correct value as he suggested.