Relations between the Sky Hue and Aerosol Scattering

Abstract

We find air pollution at every place in the northern hemisphere today; i.e., it is observed as meteorological phenomena, polar smog, yellow sand in Eastern Asia, brown haze in Southeast Asia, etc. We may see other types of polluted phenomena in addition to those obvious examples. The environmental problem becomes worse naturally without our detection; in spite of such inherent spontaneousness, it is very difficult to remove the sources. Therefore, we believe it is important that many people record conditions of the atmosphere, and detect the pollution as if becomes worse gradually, and recognize the serious situation in the future. During the stepwise recognition, it is important for us to have common consciousness and a will to remove the problem crisis.
Suspended Particulate Matter (SPM) is a kind of aerosol in the atmosphere. A simple measurement to detect the SPM is known, which is to photograph the sky by using a digital camera. We discuss the backgrounds and limitations of the method. On the Red-Green-Blue (RGB) tri-color system, we define the relation between RGB-intensities and the wavelength. Where, the hue angle is evaluated and the meaning of existence of purple color is discussed. And, it is discussed that B/R and G/R ratios depend on scattering intensities of particles. As an example, we show the B/R and G/R ratios of the haze sky. Next, we propose a method to visualize the 2-dimensional distribution of the B/R and G/R values. The method detects very dilute SPM layer in the atmosphere, which is not detected by others.
We believe that these methods are useful to detect air pollution for every person.