This top-down view solves the steady-state Gaussian plume equation analytically — no particle counting — for ground-level concentration downwind of a point source at height H, with full ground reflection:
C(x,y,0) = Q / (π·u·σy·σz) · exp(−y²/2σy²) · exp(−H²/2σz²)
σy(x), σz(x): Briggs rural, neutral (class D) dispersion coefficients
σy = 0.08x·(1+0.0001x)^−1/2 σz = 0.06x·(1+0.0015x)^−1/2
- Wind speed (u) — dilutes the plume; concentration scales as 1/u.
- Wind direction — rotates the plume axis (x,y are downwind/crosswind, not screen axes).
- Emission rate (Q) — source strength in g/s; scales concentration linearly.
- Stack height (H) — a taller stack pushes the ground-level concentration peak farther downwind and lowers it (the exp(−H²/2σz²) term shrinks as H grows until σz catches up).
- Scrubber toggle — removes ~70% of Q before it leaves the stack.
The heatmap is the exact analytic field, recomputed whenever a control changes — the same Gaussian plume approach environmental engineers use in EPA AERMOD-style tools to site air-quality monitors around factories and power plants.