Plumescape is an educational screening tool. It solves a steady-state Gaussian plume for one hour of weather, so you can see how stack design, wind and stability shape a plume. It follows the structure of US EPA dispersion models, but it is not AERMOD and its results are not a regulatory assessment.
Weather
Pasquill–Gifford stability classes A (very unstable) to F (moderately stable). Wind at stack top uses a power-law profile with the EPA rural or urban exponents. Mixing heights default to typical daytime values for classes A–D and no lid for E–F, or you can set one.
Plume rise
Briggs plume rise with the buoyancy/momentum crossover temperature, gradual rise to the final height, stack-tip downwash when exit velocity is below 1.5 × wind speed, and stable-air rise from the potential-temperature gradient (0.020 K/m for E, 0.035 K/m for F). Buoyancy-induced dispersion (Δh/3.5) is added to both sigmas.
Dispersion
Briggs open-country or urban σy and σz curves. Concentrations include ground reflection, multiple reflections from the mixing lid, and a well-mixed limit once σz exceeds 1.6 × the mixing height. In classes A–D a plume whose final height exceeds the mixing height is treated as fully penetrating and gives no ground-level concentration, as in ISC.
Hills
Hills use AERMOD's two-state idea: the concentration is a weighted mix of a plume that stays level and a plume that follows the terrain. In stable air the weight comes from the critical dividing-streamline height (Hc = hill height − u/N); otherwise the two states are weighted equally. This is a simplified version of AERMOD's method.
Comparing with WHO guidelines
Results are 1-hour averages. Where the WHO 2021 guideline uses another averaging time, the 1-hour result is scaled for comparison: 24-hour = 0.6 × 1-hour (AERSCREEN factor), 10-minute = 1.43 × 1-hour (power law, exponent 0.2).
- NO₂ 200 µg/m³, 1-hour
- SO₂ 500 µg/m³, 10-minute
- CO 35 mg/m³, 1-hour
- PM₁₀ 45 µg/m³, 24-hour
- PM₂.₅ 15 µg/m³, 24-hour
Not included: building downwash, background concentrations, chemistry (NOx to NO₂), deposition, calms, and sequential hourly weather.
Using the views
- Plan: drag stacks, hills and receptors. Drag a hill's ring to resize it. Drag empty space to pan; scroll or pinch to zoom.
- Sections follow the selected stack. Drag the marker in the plan or section view to move the crosswind slice.
- Panels move by their title bar and resize from their edges. Double-click a title bar to maximise.