ExpoAir-Modelling

Dispersion suite

by Risk Exposome360° · SRG Industrial Hygiene HUB

Three dispersion engines in one workbench — a classic Gaussian plume, a Monin–Obukhov boundary-layer model with a bi-Gaussian convective treatment, and Lagrangian puff transport.

Examples — or model any source:

Scenarios

Open file

Saved in this browser. “Save file” downloads a portable .expoair.json you can reopen or share.

Emission source

Pollutant (site-wide)

Source east m

Source north m

Emission rate g/s

Stack height m

Stack diameter m

Exit velocity m/s

Exit temperature K

Meteorology

Wind speed (10 m) m/s

Wind direction (from) °

Ambient temperature K

Mixing height m

Terrain

Building downwash

Huber–Snyder wake treatment. Enable to model a nearby building pulling the plume into its turbulent wake.

Terrain

Dividing-streamline two-state (terrain-following vs horizontal-plume) weighting via a critical streamline height. Enable to add idealised hills or load real elevation (DEM).

Deposition & decay

Well-mixed-box dry/wet deposition and first-order decay. Enable to deplete the plume and report ground deposition flux.

Surface & boundary layer

Surface type

Solar elevation °

Cloud cover frac

Surface roughness z₀ m

Bowen ratio

Albedo

Receptors

Add discrete receptor points (a village, school, or monitor) to read off the summed concentration from every source.

Site & basemap

Basemap

Site origin

Latitude °

Longitude °

Peak ground conc.

188.0 µg/m³

Peak distance

0.84 km

Sources

Receptors

Boundary-layer state

Convective (CBL) · ≈ class A

u★

0.32 m/s

-18 m

w★

1.56 m/s

H flux

177 W/m²

800 m

Rₙ

442 W/m²

Peak is 470% of the WHO 24-hr 40 µg/m³ — exceedance predicted.

Modelled 188.0 µg/m³ (≈ 71.8 ppb) vs guideline 40 µg/m³. Steady-state ~1-hr estimate; scale to longer averaging periods before formal comparison.

Ground-level plan view

log scale · viridis

Concentration footprint at ground level, north up. Red outline = WHO exceedance contour. Source ● at centre.

Centreline concentration

Ground-level concentration along the plume centreline (log distance axis).

Method & limitations

Continuous Monin–Obukhov boundary-layer scaling (u★, L, w★ from the surface energy balance) replaces discrete stability classes; turbulence-based σ; and a bi-Gaussian convective vertical distribution (updraft/downdraft split). Methodology after Cimorelli et al. (2005) — the AERMOD model formulation — and Weil et al. (1997). A reduced research implementation, not the certified AERMOD executable.

Not yet modelled: full AERMAP/CTDM terrain processing & FLOWSTAR, full PRIME building wake, plume chemistry, rigorous Horst surface-depletion, 3-D met fields (CALMET), and regulatory validation. Use for screening, training and scenario comparison — not as a regulatory substitute.