Greenhouse effect Glass transmits most of the short wavelength solar radiation, but it prevents most of the long wavelength terrestrial radiation from passing through. The absorbed portion of long wavelength radiation is converted to heat, which radiates back into the greenhouse, raising the temperature inside. The same thing happens in the atmosphere, due in large measure to the H2O vapor that is present in the air. When the medium contains particles that are smaller than the wave length of the light rays, the light rays are scattered. Therefore, short wavelengths are scattered first, producing blue sky. The principal effect of dust or haze is scattering rather than absorbing. Solar radiation Pyrheliometer measures solar radiation. Maximum solar constant = 1.94 gm.cal./cm2/min. This is equivalent to 4.5 million horsepower/mile2. This figure will vary ± 2%. The average solar constant for the entire year = 0.4785 gm.cal./cm2/min. Incoming solar radiation (short wave) reaching the earth's atmosphere is distributed as follows: 25% is lost through reflection without reaching the earth. 9% is scattered back to space. 19% is absorbed by the atmosphere on its way through. 24% is directly absorbed at the earth's surface. 17% is diffused through clouds, etc. before reaching the earth. 6% is scattered to earth. Thus, 66% reaches the earth, 34% is lost without effect