A dense canopy attenuates both incoming solar radiation and wind, decoupling the sub-canopy air from the free atmosphere above. That buffering keeps the forest floor cooler and moister by day, and warmer by night, than the open air — the forest's own microclimate.
U(z) = U_ref · exp(−a·(1 − z/h)) (wind attenuation under canopy)
I(z) = I_0 · e^(−k·LAI) (Beer–Lambert radiation extinction)
RH increases as evapotranspiration accumulates in still, shaded sub-canopy air
- Canopy density — sets leaf-area index; denser canopy blocks more sun and wind.
- Time of day — moves the sun, changing incoming radiation and surface heating.
- Outside wind — free-atmosphere wind speed above the canopy top.
- Layer toggle — switches the colored particle layers between temperature, humidity and wind-speed views.
Foresters and climate scientists use exactly this buffering effect to explain why old-growth forests act as refugia for species sensitive to heat extremes as the regional climate warms.