Solar radiation and the global energy budget - Atmosphere, Weather and Climate - page 45

Figure 3.13 Mean annual albedos (per cent): (A) At the earth's surface. (B) On a horizontal surface at the top of the atmosphere.
Source : After Hummel and Reck; from Henderson-Sellers and Wilson (1983), and Stephens et al . (1981), by permission of the American
Geophysical Union.

Air is an extremely poor conductor, and for this
reason a loose, sandy soil surface heats up rapidly
by day, as the heat is not conducted away. Increased
soil moisture tends to raise the conductivity by filling
the soil pores, but too much moisture increases the
soil's heat capacity, thereby reducing the temperature
response. The relative depths over which the annual and

diurnal temperature variations are effective in wet and
dry soils are approximately as follows:

Diurnal variation Annual variation

Wet soil 0.5 m 9 m

Dry sand 0.2 m 3 m