wind_speed_msnumberdefault: 30.5–20 (step 0.5)Mean wind speed at reference height (m/s)
Higher wind speeds dilute pollutants faster, reducing peak concentrations but spreading them further downwind. Very low speeds (<1 m/s) with stable conditions produce the highest near-source concentrations.
wind_direction_degnumberdefault: 2700–360 (step 10)Wind direction in degrees (0=N, 90=E, 180=S, 270=W)
Buildings downwind of road sources receive the highest concentrations. Changing direction by 90° can dramatically shift which residential areas are most exposed.
stability_classselectdefault: DA | B | C | D | E | FPasquill-Gifford atmospheric stability class (A=very unstable, F=stable)
Class A (sunny, low wind) produces rapid vertical mixing — wide plumes, lower peak concentrations. Class F (night, calm) produces narrow, highly concentrated plumes. Class D is neutral, used for worst-case screening.
source_typeselectdefault: road-trafficroad-traffic | point-source | area-sourceType of emission source to model
Road traffic distributes emissions along the road network. A point source (stack, vent) creates a concentrated plume. Area source (industrial zone, car park) spreads emissions over a polygon.
emission_rate_g_snumberdefault: 0.10.001–10 (step 0.01)Emission rate in g/s per source unit
For road traffic, this is per 100m road segment. Typical urban arterials: 0.05–0.3 g/s NOx. Industrial stacks may emit 1–10 g/s. Concentration scales linearly with emission rate.
Default settings represent neutral stability (class D) with road traffic emissions — a standard screening scenario. Key explorations: - Use stability class F with low wind speed (0.5–1 m/s) for worst-case night-time inversion conditions - Increase emission rate for a busy arterial or motorway (0.3–1.0 g/s) - Add the roads layer for accurate source placement along the road network - Compare stability classes A vs F to understand the range of concentration outcomes - Buildings flagged in the table exceed WHO guideline values and may warrant detailed CFD or monitoring