. Compendium of meteorology. Meteorology. SOLAR RADIANT ENERGY 23 is in excellent agreement with Linlce's results [55, p. 248]. Spectral Scattering by Water Vapor. The atmosphere is, however, never pure nor dry; both dust and water vapor are ever present in varying degree. Fowle [28] examined the transmission of the atmosphere at wave lengths where water vapor does not absorb. At those wave lengths, if dust is neglected, h = /ox exp(—Saxm) exp( —s„xwm) = /ox (a„xfCx)'" = /oxax. (14) Here the transmission coefficient through one dry at- mosphere at vertical incidence is given by aa\ = exp(
. Compendium of meteorology. Meteorology. SOLAR RADIANT ENERGY 23 is in excellent agreement with Linlce's results [55, p. 248]. Spectral Scattering by Water Vapor. The atmosphere is, however, never pure nor dry; both dust and water vapor are ever present in varying degree. Fowle [28] examined the transmission of the atmosphere at wave lengths where water vapor does not absorb. At those wave lengths, if dust is neglected, h = /ox exp(—Saxm) exp( —s„xwm) = /ox (a„xfCx)'" = /oxax. (14) Here the transmission coefficient through one dry at- mosphere at vertical incidence is given by aa\ = exp( —Sax) and thi'ough one centimeter of precipitable water vapor by a-„.,x = exp( —s„x). From equation (14) or a\ = aaxflffiX, In a\ = In a^x -f- w In a„x. (15) (16) A plot of In a\ against w should yield a straight line whose slope is In a„\ and whose intercept at t« = 0 is In aa\. Hence, a„x and aa\ can be determined. As might be expected, for a given X the observed cor- responding values of In a\ and w do not fall exactly on a straight line. In order to remove random fluctuations Fowle compiled average values, but it is not clear whether he averaged values of a\ or of In a\. At any rate, Fowle plotted his average In a\ against w. The points still scatter quite a bit, but the "best" straight line was drawn through the data, and the correspond- ing flax and a„x were determined. His values of a„x are given by List [56]. Fowle [28] assumed that the X~^ law (equation (11)) applied also for scattering by water vapor and found that his transmission coefficients a^,\ were such that the scattering is greater than might be expected from the number of water-vapor molecules. He concluded from this that the water vapor existed as aggregates of water-vapor molecules (see also [76]). Moon, however, using Fowle's data, plotted the logarithm of the average a„\ against In X, and found that flwX x-2. (17) Any relation between a,„x and X (such as equation
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