Possible issue with NAM SPHU at model levels

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trhanley
Posts: 1
Joined: October 9th, 2019, 10:25 am
Registered HYSPLIT User: No

Possible issue with NAM SPHU at model levels

Post by trhanley » October 9th, 2019, 10:50 am

I've been scratching my head trying to figure out why the values I'm seeing coming out of the 3-km NAM CONUS and 2.5 km HI grid files (e.g. hysplit.t00z.namsf00.CONUS and hysplit.t00z.namsf.HI) seem to have specific humidity values at model levels 2 and 10 that appear to be much higher than the values in the neighboring levels. I went back and looked at some older files and found this was not the case before the 21 Mar 2017 NAM upgrade (https://www.weather.gov/media/notificat ... pdates.pdf), so I suspect that changed something. I don't see any issues with any of the other variables at those levels, only specific humidity (SPHU). I'm thinking that perhaps model level 2 and 10 somehow got mixed up with heights of 2 and 10 meters and that those are what are written out into the files, based on how close the values are to the first model level. I don't think the issue affects the model itself, only what is written out into these HYSPLIT files, as if the 10th model level were biased high, I would expect that to bleed over into levels 9 and 11, but I'm not seeing that.

I'm using a custom file reader I wrote in Matlab, so I want to make sure this isn't some mistake I made with my reader and was wondering if anyone else could confirm what I'm seeing.

I realize this is not a bug in the HYSPLIT software itself, so I apologize it this is the wrong place to post this.

Thanks for any assistance!

barbara.stunder
Posts: 336
Joined: November 9th, 2012, 4:23 pm
Registered HYSPLIT User: Yes

Re: Possible issue with NAM SPHU at model levels

Post by barbara.stunder » October 15th, 2019, 12:38 pm

We are working on an operational fix, then will need to fix the archived files. This applies to all the "nams" files.

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