The radiation balance of a soil surface can be written as: R=[(H+H)-(+H)×a]+(G-E) =(1+H)(1-0)-r where r is the net radiation received per unit area. I is the sun directly radiation, H is atmospheric radiation; ais the albedo and represents the fraction of r which is reflected by the soil surface, G is the incoming longwave radiation, E is the longwave emission of the surface• The radiation balance of a soil surface can be written as: • R = [(I+H) – (I + H)×α] + (G – E) • = (I + H) (1 - α) – r • where R is the net radiation received per unit area. I is the sun directly radiation, H is atmospheric radiation; αis the albedo and represents the fraction of R which is reflected by the soil surface, G is the incoming longwave radiation, E is the longwave emission of the surface