Dispersion Modeling Calculator

Downwind concentration from AERMOD-style Gaussian dispersion.

Emission rate (g/s)

Wind speed (m/s)

Effective stack height (m)

Downwind distance (m)

Stability class (1=A…6=F)

Tab to move between fields

Ground concentration (µg/m³)

265.67

Max ground conc. (µg/m³)276.66

Max conc. distance (m)850

σy horizontal dispersion (m)38.5

σz vertical dispersion (m)24.4

Plume width at 10% (m)165.4

How to Use This Calculator

Enter Emission rate (g/s), Wind speed (m/s), and Effective stack height (m).
Set Downwind distance (m) and Stability class (1=A…6=F).
Review the Ground concentration (µg/m³) result.
Use Max ground conc. (µg/m³) and Max conc. distance (m) to inform your decision.

How the result changes with Effective stack height (m)

Emission rate (g/s): Pollutant mass emission rate from the source in grams per second.
Wind speed (m/s): Mean wind speed at stack height in meters per second.
Effective stack height (m): Physical stack height plus plume rise in meters.
Downwind distance (m): Distance downwind from the source along the plume centerline.
Stability class (1=A…6=F): Pasquill stability class. 1=A (very unstable, sunny), 4=D (neutral, overcast), 6=F (stable, nighttime).

Ground concentration (µg/m³): Ground-level centerline concentration at the specified downwind distance.
Max ground conc. (µg/m³): Maximum possible ground-level concentration from this source.
Max conc. distance (m): Downwind distance where maximum ground-level concentration occurs.
σy horizontal dispersion (m): Horizontal dispersion coefficient at the downwind distance.
σz vertical dispersion (m): Vertical dispersion coefficient at the downwind distance.
Plume width at 10% (m): Approximate plume width at 10% of centerline concentration (≈4.3σy).

Identify Input Parameters
4 parameters
Emission rate (g/s) = 10, Wind speed (m/s) = 3, Effective stack height (m) = 30, Downwind distance (m) = 1000 = 5 input(s) provided
Calculate Ground concentration
Ground concentration = concentrationGM3 * 1e6
265.673 = 265.673
Calculate Max ground conc.
Max ground conc. = cMax * 1e6
276.663 = 276.663
Calculate Max conc. distance
Max conc. distance = pow(targetSigmaZ / coeff.az, 1 / coeff.bz)
850 = 850