1 Example 10 Particle Dispersion Configure HYSPLIT to emit 500 particles over 1 hour between 10 and 3000 m (the depth of the 3 Florida trajectories from Example 8) and observe the dispersion each hour over a 9 hour period.

2 Run particle dispersion model with NAMF12 forecast data from the Workshop archive.

3 Choose Source Location Enter a starting location at: N and W

4 Total run time: 9 hours Source top height: 3000 m AGL Source bottom height: 10 m AGL Particle dump interval: 1 hour Number of particles released per cycle: 500 (minimum) Request Dispersion Run

5 Submit the job and view the results

6 When complete, the model results page will include a link to the animation. Particle Dispersion Results Notice how the particles are moving away from the source to the east at the higher levels and toward the southwest at the lower levels, as was expected based on the 3 trajectories computed earlier. Also notice how the particles become few and far between with time (indicating too few particles). Use the back button on the browser to rerun the case with 5000 particles (no rerun option exists yet).

7 Number of particles released per cycle: 5000 Request Dispersion Run

8 Submit the job and view the results

9 Particle Dispersion Results Running HYSPLIT with 5000 particles shows the same pattern as before, but with many more particles helping to define the plume shape. The red line attempts to create a cross-section through the bulk of the plume, the result of which is displayed below the map. Particles are color-coded based on their position above the ground.