ABSTRACT
The direct and diffuse radiation together received on a unit horizontal surface is termed the global radiation. The albedo of bare soil depends on the water and organic matter content, on soil texture and, again, on the angle of incidence of the radiation. Reflectivity decreases with increasing wetness as radiation is trapped by internal reflection in soil pores. The intensity of direct radiation from the sun is a crucial factor when it comes to recording sunshine as opposed to radiation. Sunshine recorders may be of two types, the first utilizing the heating power of the radiation, the second the chemical action produced by visible and ultra-violet rays. Air temperature over land depends on the fraction of net radiation that is used in heating the air via the ground, plus any energy brought in by the air motion. The lowest temperatures are experienced in August, in the middle of the cloudiest season with marine influences at a maximum.
