Context: When the Sky Turns Purple
July 18, 2026: Salem reports haze hanging around. Pittsburgh declares purple-pain air quality alerts canceling outdoor activity. British Columbia's Big Bar Lake wildfire burns. These aren't abstract headlines—they're extinction coefficients falling across our canopy.
ISS070-E-008930: Wildfire smoke column observed from orbit. NASA Public Domain.
When smoke blankets the Wasatch Front, two mechanisms kill yield:
- Light Extinction: Particulate matter scatters PAR (400–700nm). Net radiation drops non-linearly with optical depth.
- Stomatal Closure: Ozone and ultrafine particles trigger guard-cell collapse. CO₂ intake halts even if photons remain.
This tool maps AQI PM2.5 and visual range to expected Gross Photosynthesis Suppression (%) for Utah's five major crops.
Calculator
Model Parameters
The suppression rate derives from three coupled equations:
- Optical Depth (τ): τ = k × (PM2.5 / 10)^(1.3)
- PAR Transmission: T_PAR = exp(-α × τ)
- Net Suppression: S_net = (1 - T_PAR^β) + γ × f_ozone(PM2.5)
Coefficients by species:
| Species | k | α | β | γ (ozone sensitivity) |
|---|---|---|---|---|
| Alfalfa | 0.084 | 0.62 | 0.85 | 0.31 |
| Barley | 0.071 | 0.58 | 0.79 | 0.24 |
| Potato | 0.095 | 0.71 | 0.92 | 0.42 |
| Corn | 0.063 | 0.54 | 0.73 | 0.19 |
| Tomato | 0.102 | 0.76 | 0.96 | 0.48 |