Impact of the HYSPLIT model top to trajectories

Topics about the HYSPLIT trajectory model.
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michael_wrf
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Joined: May 27th, 2022, 5:56 am
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Impact of the HYSPLIT model top to trajectories

Post by michael_wrf »

Hello,

I am running the HYSPLIT model with WRF input data. The WRF simulation is aimed on leeside warming of a mountain range (max. elevation about 1300 m ASL). The WRF model top is 25 hPa (ca. 25 000 m). I would like to compute trajectiories in HYSPLIT to get information about the source region of subsiding air. However, I am a bit confused by the impact of the option Top of model in HYSPLIT (under Trajectory - Setup run) on computed backward trajectories.

When this parameter is set to 25 000 m, the trajectory is short and stops just before the mountains.
Computed trajectory for HYSPLIT model top 25 000 m
Computed trajectory for HYSPLIT model top 25 000 m
When set to 40 000 m the trajetory is reasonably long with regard to environmental wind speed and gets to > 1500 m ASL
Computed trajectory for HYSPLIT model top 40 000 m
Computed trajectory for HYSPLIT model top 40 000 m
For 100 000 m, the trajectory is very similar but not completely the same as for 40 000 m.
Computed trajectory for HYSPLIT model top 100 000 m
Computed trajectory for HYSPLIT model top 100 000 m
I am thus wandering what setup of HYSPLIT model top is the best for my case and why there are the differences.
I am enclosing trajectories for all cases.

Thank you very much!
Michael
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