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Odor Source Back Trajectory

Posted: June 16th, 2021, 9:26 am
by mcwilliams@coj.net
. I am a regulator, and we respond to odor complaints. I often use trajectories to get an idea of which facility might be the odor source (this is independent of sending inspectors in the field). I run trajectories using online HYSPLIT with HRRR (archive or forecast) at a height of 10 m AGL (Jacksonville Florida so no terrain issues). The distance of interest is 2 to 10 miles. Many times trajectories have provided useful information. Sometimes not. Any thoughts on our setup?

Re: Odor Source Back Trajectory

Posted: June 16th, 2021, 9:56 am
by christopher.loughner
Your setup seems fine. You may want to consider making multiple trajectories with multiple starting heights. HRRR is the highest resolution met product that we have available on READY, so that is a good choice. I suggest comparing HRRR winds with observations to get an idea on model error. Note that HYSPLIT and the met products that are available on READY do not include urban building impacts, so HYSPLIT cannot accurately simulate trajectories through a complex urban environment.

If meteorological observations are available, some users may want to consider using user entered meteorology for short range trajectories, but not in your case since your are located near a coastline with complex sea / land breeze circulations.

Re: Odor Source Back Trajectory

Posted: June 17th, 2021, 9:16 am
by mcwilliams@coj.net
We often receive many odor complaints on days when there is an overnight, running into early morning temperature inversion. Would it make sense to set the height to "Automatic mid-boundary layer height?" (option in online version of HYSPLIT)?

Re: Odor Source Back Trajectory

Posted: June 17th, 2021, 9:55 am
by alicec
Yes this would be a good option to use. It would be good to use that option in conjunction with a few fixed heights to
get an idea of how sensitive your results are to starting height.