Generating Daily Extremes for Local Timezone

[jbellino]

Hello,

I'm currently running WRF with output_diagnostics = 1 so I can get daily minima/maxima for my runs and I want to be sure that I'm using the inputout_begin_h option correctly. I want WRF to calculate the minima/maxima for the 24-hour period coincident with Eastern Standard Time (USA) so I've set "auxhist3_begin_h = -5" in my namelist file. Does this work in the way that I'm imagining it does? The closest thing I've found to an answer is this thread in which the user states:

Since I need daily extremes of temperature, I set my wrfxtrm interval as 1440 (one day) and the wrfxtrm_begin_h=17

The expected output is to have files save at 17:00:00 for each day to match the UTC time with the Local time.

but they do not specify which timezone they are converting to and I want to be sure the "-5" is working the way I want it to and that I'm not supposed to use "+19" instead.

And further, I see the description of the output variable TT2MIN as "TIME OF MINIMUM TEMPERATURE AT 2M HEIGHT IN DIAGNOSTIC OUTPUT INTERVAL". Does the "diagnostic output interval" refer to the modified time with respect to wrfxtrm_begin_h or to the simulation time of the model?

Thanks!

 

[kwerner]

Hi,
The value given to auxhist3_begin_h corresponds to the simulation hour. There is no conversion for different time zones. All times used in WRF are in UTC (Z). For e.g., if you are running a simulation from 2023-01-01_12:00:00 to 2023-01-03_00:00:00, and you don't need the output diagnostic variables until 2023-01-02_00:00:00:00 (12 hours into the simulation), you can set auxhist3_begin_h = 12.

I believe the value given for TT2MIN will be similar - the model integration time (not taking into account the begin_h time you used). You can test this to make sure.

 

[jbellino]

Thank you for your reply. So, the value given to auxhist3_begin_h, "-5" in my case, tells WRF when I want the output diagnostic variables to start. And if I have auxhist3_interval set to 1440, does this mean that the diagnostic variables will then be given every 1440 minutes from that point onward? So that I can effectively set the beginning of the tracking of the output diagnostic variables to be offset from the internal time in UTC? More directly, by using "-5" am I getting once-daily minima and maxima for these variables accordant to an interval that would be considered 00:00 to 24:00 Eastern Standard Time (i.e. 05:00 to 05:00 UTC)?

 

[jbellino]

More directly, by using "-5" am I getting once-daily minima and maxima for these variables accordant to an interval that would be considered 00:00 to 24:00 Eastern Standard Time (i.e. 05:00 to 05:00 UTC)?

Ok I think I've answered my own question after having plotted up some of the results I've gotten so far. Given the location of the minimum value at the change of date at midnight (UTC) Jan 3-4 it seems that there is no shift in the 24-hour period being reported, just a change in when the reporting starts.

 

[kwerner]

I'm glad you were able to see the results. Sometimes the best way to understand the settings is to play around with values and visualize the results.

I don't believe you would use a negative value for the auxhist3_begin_h parameter, though. That would indicate you wanted to start the output 5 hours prior to the start of the simulation.

 

[jbellino]

I don't believe you would use a negative value for the auxhist3_begin_h parameter, though. That would indicate you wanted to start the output 5 hours prior to the start of the simulation.

Right, this would only make sense in the context of trying to match time zones, which this option does not do. Thanks!