Hysplit options related to horizontal/vertical dispersion

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hlbutterfly
Posts: 10
Joined: September 30th, 2020, 10:56 am
Registered HYSPLIT User: Yes

Hysplit options related to horizontal/vertical dispersion

Post by hlbutterfly »

Dear all,

I am doing a very simple CH4 concentration simulation from a single point continuous source, using both pure puff (initd=1) and hybrid (initd=3) mode and HRRR met. data. The simulation last for an hour and with the hybrid mode I am using 15000 particles in total. I am using mostly default parameters. However, the vertical and horizontal dispersion results seem unreasonable in the following aspects:

(1) The horizontal spread is much bigger than the same simulation performed with calpuff or observation.

About ~200m downwind the source, the sigma y of the plume calculated from Hysplit is about 80 m while Calpuff's results and observations suggest a sigma y of only 8~9m.

(2) Vertical dispersion seems sudden.

I am seeing weird Hysplit results vertically during the daytime. For instance, during the time day, the concentration gets dispersed vertically almost instantaneously. Calpuff seems to give more reasonable and smooth vertical dispersion.

There seems to be several configurations that are related to the vertical mixing, for example, kmix0, kblt, kzmix, etc. but I am not sure which one or ones are important. Can anyone suggests which options or parameters that I should pay attention to, with respect to dispersion? I am attaching my CONTROL and SETUP.CFG file for reference. Is there anything wrong with my settings?

Thank you very much!
SETUP.CFG.txt
SETUP.CFG
(863 Bytes) Downloaded 77 times
CONTROL.txt
CONTROL
(725 Bytes) Downloaded 32 times
alicec
Posts: 338
Joined: February 8th, 2016, 12:56 pm
Registered HYSPLIT User: Yes

Re: Hysplit options related to horizontal/vertical dispersion

Post by alicec »

HYSPLIT minimum time step is currently 1 minute and it looks like you are trying to use
very high spatial and temporal resolution.

It looks like you have
horizontal resolution of 0.0001 degree = 1m
Total domain size of 0.006 degree = 666m
1 vertical level only 0-2 m.
output every 1 minute.
3km HRRR as NWP input

Some of the conversation here regarding use of HYSPLIT at very high spatial and temporal resolutions may be useful.
viewtopic.php?f=28&t=2308
hlbutterfly
Posts: 10
Joined: September 30th, 2020, 10:56 am
Registered HYSPLIT User: Yes

Re: Hysplit options related to horizontal/vertical dispersion

Post by hlbutterfly »

Alice,

Thank you so much for the reply! We read carefully of the other post you pointed. Based on our interpretation, given the use of HRRR or a single onsite met data and the spatial resolution our near-source application may not be appropriate for HYSPLIT? Our alternative plan is using CALPUFF. Do you agree?

Thanks
Ling
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