Search found 145 matches

by alicec
June 17th, 2019, 11:03 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

Please check that your concentration grid is large enough so that the particles are not being deposited outside of your grid.
That would cause the number of particles that you are calculating from the output file to be lower than you expect.
by alicec
June 17th, 2019, 9:52 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

1. Small particles reach a terminal fall velocity very quickly. So the gravitational settling velocity is a constant. There is extensive literature on how to estimate the terminal fall velocity of a particle given shape, size, and density. This is probably not relevant for insects though. 2. Yes - d...
by alicec
June 17th, 2019, 8:05 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

Please see this help page and some of the references quoted within. https://ready.arl.noaa.gov/hysplitusersguide/S314.htm The deposition velocity is simply defined such that the the flux of material to the surface is the deposition velocity multiplied by the concentration above the surface. e.g. (kg...
by alicec
June 14th, 2019, 2:41 pm
Forum: 2019 HYSPLIT Workshop Questions
Topic: The resistance method for particle deposition
Replies: 1
Views: 74

Re: The resistance method for particle deposition

Great - we will talk about this at the sessions on Monday and Tuesday.
Thanks for attending the workshop.
by alicec
June 14th, 2019, 11:39 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

Did you convert degrees to radians when using the cosine function in excel?
by alicec
June 14th, 2019, 10:04 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

I made an error when writing down the formula. Please see the edited answer.

The area is calculated as
(111198.323)^2 * latspan * lonspan * cos(lat)

latspan and lonspan are the lengths (in degrees latitude, longitude) of the sides of the concentration grid.
by alicec
June 13th, 2019, 7:47 pm
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

I was not able to reproduce your problem with the following CONTROL and SETUP. Using 10,000 particles each with 1 unit mass. calculating from the deposition I get 1087 particles "in" the deposition layer and the MESSAGE file indicates 8913 particles left in the simulation. Also - yes you are correct...
by alicec
June 13th, 2019, 5:10 pm
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

I'm editing this answer because I made a mistake in writing down the formula for the area. So you are getting more particles that you would expect from the deposition value? One thing to take into account is that your deposition grid area may not be square – depending on your location. The area is c...
by alicec
June 12th, 2019, 11:15 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

Questions 1 & 2 – With ichem=5 the deposition routine will transfer the entire mass of one particle to the deposition layer. So you can think of that particle as now being in the deposition layer and you are not going to be double counting it. (The fact that it stays in the particle array with 0 mas...
by alicec
June 10th, 2019, 11:44 am
Forum: Dispersion Model
Topic: Time Step and Concentration Calculation
Replies: 35
Views: 725

Re: Time Step and Concentration Calculation

I don't know what you mean by the number of particles on the deposition layer.
Maybe if you explain what you think this number is going to represent physically in the real world or what information
you hope to get from this number I can help you better.