Search found 12 matches

by MarkCohen
April 2nd, 2018, 1:08 pm
Forum: Dispersion Model
Topic: MAXPAR/NUMPAR upper limit
Replies: 6
Views: 254

Re: MAXPAR/NUMPAR upper limit

Hi, sorry it has taken awhile to respond to your last question. In looking at your questions in this thread, I think the key issue is a what a HYSPLIT "particle" really represents. The "particles" being released and tracked in a HYSPLIT simulation (using the default dispersion mode: 3-D particle) sh...
by MarkCohen
March 8th, 2018, 9:26 pm
Forum: Trajectory Model
Topic: Initial heights and mixed layer depth
Replies: 2
Views: 406

Re: Initial heights and mixed layer depth

Hello! Thank you for alerting us to this issue, and our apologies for taking so long to respond. First, thanks for providing the details that you did, and for very clear explanations (with color coding!). With the information you provided, I was able to attempt the same runs here (i.e., same startin...
by MarkCohen
October 18th, 2017, 5:30 pm
Forum: General Comments
Topic: Eulerian Approach
Replies: 1
Views: 686

Re: Eulerian Approach

Hi, yes, I think that you are "right" in the way you are thinking about this, but I will try to elaborate briefly. The quoted statement you mention is contained in the following reference: Draxler, R. R. and G. D. Hess (1998). "An overview of the HYSPLIT_4 modeling system of trajectories, dispersion...
by MarkCohen
June 9th, 2017, 11:08 am
Forum: Users
Topic: Is there a way this can be done?
Replies: 4
Views: 888

Re: Is there a way this can be done?

Hi, one more aspect of this to mention. Note, there is another way to do this, "outside" of the GUI. Basically, you can take any tdump file and edit it to create a simple text file that you can import into your GIS program. Here is what I have done in ArcGIS / ArcMap. There are probably a number of ...
by MarkCohen
June 8th, 2017, 9:59 am
Forum: Users
Topic: Is there a way this can be done?
Replies: 4
Views: 888

Re: Is there a way this can be done?

Hi Quaymat321234, I will try to take a look at this as soon as I can, but it will probably be a few days. Thanks for your question and your patience : )
by MarkCohen
October 17th, 2016, 2:57 pm
Forum: Trajectory Model
Topic: Question about back trajectories starting blow PBL
Replies: 5
Views: 737

Re: Question about back trajectories starting blow PBL

Hi Ren2014, In general, yes, higher-resolution meteorology should usually give more "accurate" trajectories. All things being equal, one could always pick the highest resolution meteorological data available for a simulation. Note that trajectories will stop once they leave the domain of the met dat...
by MarkCohen
October 11th, 2016, 11:40 am
Forum: Trajectory Model
Topic: Question about back trajectories starting blow PBL
Replies: 5
Views: 737

Re: Question about back trajectories starting blow PBL

Hi Ren2014, You can absolutely start back trajectories below the PBL, and in fact, this is probably done in the majority of cases in which back-trajectories are run. It basically depends on the problem you are investigating with the back-trajectory. If, for example, you are wondering where the air c...
by MarkCohen
August 23rd, 2016, 3:33 pm
Forum: Users
Topic: Surface and near surface trajectories - soliciting input
Replies: 1
Views: 414

Re: Surface and near surface trajectories - soliciting input

Hi John, I'm not quite sure what you are asking about. Is it any of these: 1. In a forward "concentration" simulation, what vertical levels should be used for a concentration grid? 2. In a forward "trajectory" simulation, what should the starting height be for a source? 3. In a backward "trajectory"...
by MarkCohen
August 11th, 2016, 6:48 pm
Forum: Dispersion Model
Topic: Integrate over time series
Replies: 11
Views: 1546

Re: Integrate over time series

Hi Stephen, I'm so glad to hear that it is working for you! Regarding additional data layers, I can give you a few suggestions. (1) Your idea of using Google Earth is a good option. As you know, you can run concplot (Concentration -> Display -> Contours) with the option of exporting Google Earth out...
by MarkCohen
August 8th, 2016, 1:36 pm
Forum: Dispersion Model
Topic: Integrate over time series
Replies: 11
Views: 1546

Re: Integrate over time series

Hi Stephen,

The concentration grid layer levels are specified when you specify the concentration grid. The image below shows the steps you'd take to do this in the GUI:
Picture1.png