Yoshida - 1981 - Fundamentals of Rice Crop Science

86 FUNDAMENTALS OF RICE CROP SCIENCE
Outside the earth’s atmosphere, a surface normal to the sun’s rays receives
energy at a mean rate of approximately 2 cal/cm 2 per minute, known as the solar
constant. The amount of solar radiation received at any location on the earth’s
surface is a modification of the solar constant by two factors: the geometry of the
earth with respect to the sun; and the absorption, reflection, and scattering in the
atmosphere. As a consequence, the actual maximum radiation received at the
2.14. Solar radiation in some of the world’s major rice-growing areas (Yoshida 1978).