. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography ~i i r 60 40 30 AIR MASS 20 20 n i i i 30 40 60 DEC. 1, 1964 DEC. 8, 1963 "l 1. Figure 2. Direct solar radiation data for Amundsen-Scott (South Pole) Stationsj Antarctica (after Viebroek and Flowers3 1968). for determining long-term changes in atmospheric transmittance, it is not a quantitative measure of turbidity as are the classical turbidity terms. The important question that must be answered concerning geophysical monitoring is: what measu
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography ~i i r 60 40 30 AIR MASS 20 20 n i i i 30 40 60 DEC. 1, 1964 DEC. 8, 1963 "l 1. Figure 2. Direct solar radiation data for Amundsen-Scott (South Pole) Stationsj Antarctica (after Viebroek and Flowers3 1968). for determining long-term changes in atmospheric transmittance, it is not a quantitative measure of turbidity as are the classical turbidity terms. The important question that must be answered concerning geophysical monitoring is: what measurement accuracy and what time period is re- quired to resolve a long-term trend to a certain resolution? If we ap- ply the turbidity trend problem to this question, we have the following result. If we assume a change in radiation intensity of percent per decade, based on Davos data (McCormick and Ludwig, 1967), and assume a need to resolve this change to one part in 10, then an percent ac- curacy in long-term series of measurements will require 18 years of data to obtain the necessary resolution of the trend. Similarly, an accuracy of percent will require 36 years of data in order to obtain the spec- ified resolution. Angstrom's turbidity factor, a, also critically depends on the ac- curacy of the intensity measurement. For example, with an instrument accuracy of percent, it is possible to resolve a only to about 50 percent, in the normal range of values. The turbidity factor a is use- ful because it provides a single index measure of the size distribution of the aerosol particles. Use of the word accuracy is a problem in semantics. For a long- term geophysical monitoring program, it is necessary to reproduce the same radiation scale in a series of instruments to be employed over a 1275. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may
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