ambient_wind_speed_msnumberdefault: 40–20 (step 0.5)Reference wind speed above rooftop level
Canyon wind speed scales linearly with ambient wind speed. Low ambient speeds (<2 m/s) often result in stagnant skimming-flow canyons failing to meet ventilation targets.
wind_direction_degnumberdefault: 2700–360 (step 10)Prevailing wind direction in degrees (0=N, 90=E, 180=S, 270=W)
Wind perpendicular to a canyon drives cross-canyon flow; wind parallel drives along-canyon flow. Oblique angles produce intermediate regimes. The model applies higher attenuation for across-canyon winds.
target_achnumberdefault: 61–30 (step 1)Target air changes per hour for natural ventilation
Residential natural ventilation typically requires 4–6 ACH. Urban air quality standards may demand higher values in polluted areas. Reducing the target will show more streets meeting ventilation criteria.
pollutant_sourceselectdefault: traffictraffic | industrial | backgroundType of dominant pollutant source in the canyon
Traffic sources are concentrated at road level. Industrial sources may be elevated. Background represents distributed regional pollution. This affects the urgency of ventilation efficiency targets shown in the report.
Default settings represent a moderate westerly wind in a mixed-density district. Key explorations: - Reduce ambient wind speed to 1–2 m/s to identify worst-case stagnation zones - Increase target ACH to 10 for an air quality-sensitive district - Switch pollutant source to 'traffic' to assess residential exposure in canyon streets - Cross-reference results with the Pollutant Dispersion model for concentration estimates