FAQs Dispersion Parameters

There is no height variable available to model in Playground. The model is set to output surface concentrations, that is, first 100m above ground. The XY limits reduce the length and width of the domain to that area surrounding your fire location, therefore there are fewer meteorological grids for the model to resolve, thus decreasing the time it takes for the model to run.

The number of particles and the grid resolution are two different (yet, still related) things.

HYSPLIT runs in particle mode, meaning that it uses thousands of particles to simulate the emissions. The greater the number of particles, the more improved the solution. But also, the greater the number of particles, the longer it takes for the model to run.

The grid resolution here refers to the gird sizes of the dispersion output. The higher the grid resolution (i.e., the smaller the size of each grid, and thus a larger number of grids), the more calculations the model needs to do. This also increases the time it takes the model to run, but it does help resolve complex terrain features.

In both cases, the decision should be selecting between an improved solution versus runtime.

Remember that the two options are not mutually exclusive. If the user wants to attain an improved solution by just picking one (increasing the number of particles or increasing the grid resolution), we suggest increasing the grid resolution.