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how to set the prec_acc_dt properly?

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Dear Colleges,

I need to set the prec_acc_dt to 180 min, assuming total precipitation amount for the last three siulation hours (prec_acc_nc).
However, after setting the prec_acc_dt = 180, 180, in the &physics section (the namelist.input is attached), the wrfout files show accumulated precipitation amount for the last one hour (60 min). I checked that comparing the wrfout files at different time steps for my d02.
I think this might be due to setting the history_interval = 360, 60, i.e 60 min for d02. Or maybe I am wrong, it just use the default value?

However, I need to set history_interval to 60 min to have more frequent output of other variables (not precipitation).
Is it possible to solve this issue?

Best regards,


  • namelist.input.txt
    6.3 KB · Views: 85
1) Can you let me know which version of the model you are using?
2) Can you run this again, but first set debug_level = 0. We don't recommend setting this, as it rarely provides any insightful messages and simply add a lot of junk to your log files, making them hard to read through.
3) Once you rerun without the debug option, I assume you will still see the same problem. If so, please attach your rsl.out.0000 file (or running log file if you don't have rsl.* files), along with one of your wrfout_d02* files so that I can take a look. If the file is too large to attach, and you don't have another method to link the file to me, please see the home page of this forum for instructions on providing large files.

Dear Kelly,

1) I am using WRF V4.0.
2) I re-run the model with debug_level = 0 for 18 hours (see the nemelist.input file).
3) The all needed files can be downloaded at:

Please, check the PREC_ACC_NC in the wrfout_d02_2019-04-17_13:00:00 showing the simulated precipitation amount over the last one hour, i.e. the RAINNC in the wrfout_d02_2019-04-17_13:00:00 - RAINNC of wrfout_d02_2019-04-17_12:00:00.

However, in my namelist.input file I set prec_acc_dt = 180, 180, and I expect that the PREC_ACC_NC in the wrfout_d02_2019-04-17_13:00:00 should be equal to RAINNC in the wrfout_d02_2019-04-17_13:00:00 - RAINNC of wrfout_d02_2019-04-17_10:00:00.

Best regards,
I believe this is behaving properly. Because you have this set to 180, that means that the value starts over after each 3 hour cycle. This means that prec_acc_nc at hour 12 should be the total RAINNC that accumulated over hours 10, 11, and 12, and then at hour 13 it starts over with only the total that accrued since the previous hour. So:

prec_acc_nc (hour 10) = RAINNC(hour 10) - RAINNC(hour 9)
prec_acc_nc (hour 12) = RAINNC(hour 10 - hour 9) + RAINNC(hour 11 - hour 10) + RAINNC(hour 12 - hour 11)
prec_acc_nc (hour 13) = RAINNC(hour 13 - hour 12)

I took a point in your domain and determined that the calculation works out correctly.

Dear Kelly,

Thank you so much for your kind explanations! Now it is clear for me how the prec_acc_nc is estimated.

Best regards,