Solar radiation reaching the surface comes in three measured forms: direct radiation (line-of-sight from the sun), diffuse radiation (scattered from the rest of the sky), and shortwave total (direct + diffuse). Open-Meteo reports all three. The integrated quantity drives outdoor photochemistry, the UV portion drives sunburn and vitamin D, and the visible portion drives indoor lux through windows.
For air chemistry, the photochemistry articles (ozone, cloud cover) cover the ozone production mechanism. The dashboard reads shortwave radiation as the most direct input to photochemical forecasts; cloud cover modulates it. A 600 W/m² direct radiation reading at solar noon is a strong ozone-production day; a 200 W/m² reading on the same date is a low ozone day.
For human exposure, UV is the relevant fraction. UV index (see UV index) condenses the harmful UVA + UVB portion into a single number for daily decision-making. Vitamin D production and skin damage both scale with UV; the indoor population receives much less of both because most window glass blocks UVB.
For circadian biology, the relevant signal is indoor visible-light intensity (lux) measured by the OPT3001 sensor. Indoor lux from window-transmitted shortwave radiation is the dominant input to the circadian system for most adults during waking hours; see lux and circadian and ambient context. The dashboard reads outdoor shortwave radiation and indoor lux together: a sunny outdoor day with low indoor lux suggests the user is not getting adequate window exposure.
References
- EPA - Ground-level ozone basics www.epa.gov
- WHO - UV index Q&A www.who.int
- Open-Meteo - Forecast API documentation open-meteo.com
- Jacob - Introduction to Atmospheric Chemistry (Harvard) acmg.seas.harvard.edu
