3. Surface albedo effects and the heating of soils (Walter Jehne)
When the solar radiation that has not been absorbed by the liquid humid haze micro-droplets reaches the Earth’s surface it is either reflected back into the air and out to space or absorbed by that surface. The albedo effect measures the level of this reflection. White reflective surfaces such as clean snow may reflect 90% of the incident 300+ w/m2 whereas dark surfaces such as bare soils, may reflect less than 10% of this incident heat.
The level of ground cover, be it by suspended leaves, pastures or litter will also influence how well that surface is insulated and protected from warming by the solar radiation that was not reflected.
Similarly the organic matter and thus moisture content of the soil will also influence the ability of soils to absorb heat and the degree to which its temperature will rise as a consequence.
Thus soils that are well protected and insulated mostly can’t absorb enough solar heat to get warmer than 20oC. By contrast bare, dry, dark unprotected soils in full tropical sunlight will often have very low albedo levels and absorb most of the incident heat and warm up to over 50 and even 70oC.
Walter explains surface albedo effects in this video at about 1.03.35.