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### Re: Vertical Mass Distribution

Posted: **February 16th, 2021, 9:48 am**

by **mingwang**

Dear alicec,

Thanks for your reply.

So the settings for the simulation attached in my previous post are correct?

I am just wondering if NUMPAR is set to be 15,000,000 (1 particle is equivalent to 1 mass unit), but HYSPLIT actually released 9,289,945 particles. What did happen to the missing particles (5,710,055 = 15,000,000 - 9,289,945)?

After the simulation, I calculated the total number of particles in the model. There were 14,987,809 (~15,000,000) particles including both particles suspended in the atmosphere and particles deposited on the ground.

Did those particles (5,710,055) immediately fall to the ground in the release locations? Is that why they were not shown in the message file? Or other reasons?

Thank you very much for your help, again.

Kind Regards,

Ming

### Re: Vertical Mass Distribution

Posted: **February 17th, 2021, 4:16 pm**

by **alicec**

A few observations

-Your source locations are only 1m above the ground. You may want to revisit this choice.

https://www.ready.noaa.gov/hysplitusersguide/S310.htm
-you are using ichem=5

https://www.ready.noaa.gov/hysplitusersguide/S628.htm
If you use ichem=5, then whole particles are deposited rather than a fraction of the mass of a particle. Once those particles are deposited they are removed from the simulation and will no longer appear in the MESSAGE file.

You have a particle size, density and shape defined which means your particles will gravitationally settle.

Your particles are pretty large – 2.76mm. And you are using the Ganser formulation which is appropriate for large particles.

The density of your particles is very small - 0.0012g/cc. This is close to the density of air which doesn't make sense.

https://www.ready.noaa.gov/hysplitusersguide/S314.htm
Because your particles are not very dense, the gravitational settling will be small. But as they are starting at 1m, they are already in

the lowest layer where a certain percentage of them will be removed for deposition.

With this combination, yes, a lot of the particles will immediately be deposited on the ground and removed from the simulation.

### Re: Vertical Mass Distribution

Posted: **February 18th, 2021, 8:40 am**

by **mingwang**

Dear alicec,

Thank you very much for your reply. Your explanation is very helpful. It all makes sense to me now.

I would like to confirm something about the multiple sources (emission area) with you.

I notice that we are able to specify the size of the source with its emission rate.

3(1)- Enter starting location (lat, lon, meters, Opt-4, Opt-5)

So Opt-4 will override the value of the emission rate (line 12-2), if Opt-4 is specified? Am I correct?

If I specify a source (Opt-5) as 600 m2 and Opt-4 is specified as 100 particles/hour (1 particle = 1 mass unit) and the emission duration is 6 hours, how HYSPLIT will choose the release locations within that area (600 m2) to release 100 particles for each hour?

Does HYSPLIT randomly pick up a location in the area of 600 m2 to release 100 particles for each hour?

It would be great if you could give me an example to describe it.

Your help would be much appreciated. Thanks.

Kind Regards,

Ming

### Re: Vertical Mass Distribution

Posted: **February 25th, 2021, 10:26 am**

by **alicec**

Yes you are correct.

opt-4 will over-ride the emission rate in line(12-2).

https://www.ready.noaa.gov/hysplitusersguide/S310.htm
If you specify opt-5, an area, then the initialization will randomly distribute particles

over that area. The fortran random number generator is used for this purpose.

If you have a complex emissions setup then consider using an

EMITIMES file.

https://www.ready.noaa.gov/hysplitusersguide/S417.htm

### Re: Vertical Mass Distribution

Posted: **February 26th, 2021, 9:56 am**

by **mingwang**

Dear alicec,

Thanks for your reply and help.

'The initialization will randomly distribute particles over that area.'

If a source (Opt-5) is specified as 600 m2 and the emission rate (Opt-4) is specified as 100 particles/hour (1 particle = 1 mass unit) and the emission duration is 6 hours,

HYSPLIT will randomly distribute 100 particles over 600 m2 for each hour (i.e. HYSPLIT will reset the random distribution process every hour)?

Or HYSPLIT will just randomly distribute all the particles (600 particles) over 600 m2 for the whole emission duration (6 hours) once during the initialization?

Which one is the correct answer?

Your help would be much appreciated. Thanks.

Kind Regards,

Ming

### Re: Vertical Mass Distribution

Posted: **March 4th, 2021, 9:55 am**

by **alicec**

I'm not sure I understand the question.

HYSPLIT will create/emit new computational particles at every time step during the emission time period.

When the emission routine is called at each time step, it distributes the new particles

over the specified area by adding a randomly chosen displacement to the center point.

### Re: Vertical Mass Distribution

Posted: **March 12th, 2021, 5:56 am**

by **mingwang**

Dear alicec,

Thank you very much for your reply and help. You have answered my questions. It all makes sense to me now. Thanks.

Kind Regards,

Ming

### Re: Vertical Mass Distribution

Posted: **March 29th, 2021, 2:20 pm**

by **lefebvre**

I am having a similar issue where if I integration the average mass concentration for the first sample time I get more mass then I initialized with.

I am using PARINIT to start HYSPLIT.

The PARINIT file contains 1.03124e+09 grams of mass.

The PARDUMP coordinates this with the same mass at startup and 3.89337e+08 grams at T+1.

I would expect that if I integrate the cdump for the average mass concentration for H+1 that I would get something between 1.03e9 and 3.89e8,

but if I integrate the average mass concentration I get 1.1454183E+09 grams at T+1.

If I switch to snapshot, as opposed to average mass concentration, the T+1 mass from integrating the mass concentration is equal to the PARDUMP T+1 mass at 3.89337e+08 grams.

If I expand the sample interval from 1 hour to 6 hours, the average mass concentration drops but only slightly to 1.1348e+09. This still exceeds the PARINIT total mass.

I have attached my inputs. I attempted to attach the binary PARINIT file as PARINIT.binary.txt, but it appears to still have issues attaching.

Regards,

Jordan

### Re: Vertical Mass Distribution

Posted: **March 30th, 2021, 1:00 pm**

by **alicec**

Can you attach the MESSAGE file from the HYSPLIT run?

Thank you.

### Re: Vertical Mass Distribution

Posted: **March 30th, 2021, 1:30 pm**

by **lefebvre**

Here is the message file for the 6 hour run.

Thank you,

Jordan