Drag the time slider and watch the sun cross the sky while PPFD rises and falls. Compare summer and winter at your latitude.

Clean-atmosphere model at 100 m above sea level: sun position from the NOAA algorithm, sunrise and sunset including refraction (−0.833°), direct beam after Meinel, cloud attenuation after Kasten–Czeplak (partly cloudy ≈ 6 oktas, overcast ≈ 8 oktas). The time scale is true solar time. Dust, local climate and terrain are not accounted for — real values may differ.