Application of HYSPLIT for tracing flying insects

Post user applications of the HYSPLIT trajectory or dispersion model.
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Juhyeong Han
Posts: 1
Joined: February 8th, 2022, 10:17 pm
Registered HYSPLIT User: Yes

Application of HYSPLIT for tracing flying insects

Post by Juhyeong Han »

Hello, fellow HYSPLIT users!

I started a new project regarding tracing flying insects(pests). I wish to know where precisely the insects are originating from (using back trajectory) and to predict which region they would affect severely(using forward trajectory) for sake of crop yields and economy.

I have read many papers that utilized the HYSPLIT model to do the similar research, but none of them specifically mentioned what parameters they used and/or their rationale. Moreover, I was told that the 5.1.0 version of the model includes insect horizontal speed to trajectory calculations, but I can't find it, although I am using the very version.

I would love to ask the following example questions:
Can I put the weight of flying insects' weight in 'Density(g/cc)'? (as shown in the attachment)
Can I put the average flying velocity of insects 'Vel(m/s)'?
Can I put the size of insects in 'Particle Diameter(um)'?

Could you please give me some inspiration on parameter decisions for this project?

Thanks a lot!

Best,
Juhyeong
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MarkCohen
Posts: 17
Joined: August 5th, 2016, 11:56 am
Registered HYSPLIT User: Yes

Re: Application of HYSPLIT for tracing flying insects

Post by MarkCohen »

Hello Juhyeong,

Thank you for your interest and your questions regarding the use of HYSPLIT to track insects. I will try to provide a few answers and ideas for you to consider.

Most scientists who use HYSPLIT or a similar model to simulate insect dispersal do not treat the insects as a "particle" that would be deposited, i.e., they do not include things like the weight or size of the insect. And in fact, most applications of HYSPLIT for insects only consider trajectories, and trajectories do not include wet or dry deposition at all. Trajectories are only the movement of the air mass. The typical assumption is that the insects are simply blown along by the wind, and that they follow the air mass trajectory. So, to answer your overall question, there are really no parameters to set. You simply need to estimate the starting location and time, and then start the trajectory from there and follow it as long as you think is relevant. (or the ending location and time, and then go backwards, for as long as you think relevant)

Now, the behavior of insect flight is of course quite complicated. Recently, we have developed an App that adds a number of layers of complexity to this simulation. The app was developed for locusts, but could be used for any insect if the approach was considered to be applicable. In the "Locust Migration App" -- https://www.ready.noaa.gov/READYLocusts.php -- the locusts take off and land each day according to the user's specifications, and the locusts can be specified to fly at a certain height (or heights) by the user. This App may be potentially useful for your work if the insects take off and land each day. We also have options for the locusts to not land each day, i.e., to fly all night. But in any event, you can also just run the HYSPLIT trajectory model forward or backward to simulate any insect that is blown along by the wind. One thing you would want to think about would be vertical motion. For the locust App, the typical use is for the user to specify a height (or heights) and a "constant height" trajectory is simulated. But, other vertical motion options can be chosen in that App, and also, of course, if you are running HYSPLIT trajectories with the model in general. In fact, with HYSPLIT, the default is to use the vertical motion as determined by the vertical motion of the wind. This may or may not be what you want in simulating the insects that you are interested in.

Recently, one scientist contacted us and told us that the insect he was modeling did not necessarily fly exactly with the wind, but that had some ability to go faster than the wind. So, we added in a new parameter (VBUG) in which the user can specify an added velocity over and above the air trajectory velocity that the insects will be governed by. This parameter is not set in the Graphical User Interface (GUI) yet, though, and must be set in SETUP.CFG. The default is VBUG=0.0, but if this value is set in SETUP.CFG, then an additional velocity (m/sec) is added to the trajectory velocity at each step of the way.

I hope this helps.
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