(Received: July 15, 2008; Accepted for publication: October 17, 2008; Advance publication: November 25, 2008)
We propose a method to get information about the SPM density and the characters in the sky. We use the spectrum of the moonlight for night observations, and adopt color indexes that are calculated from RGB-data of digital photography for the daylight cases. We show a diffractive optic to get the spectrum, and make correlations between the color index and the SPM density. Using these approaches, we observed the SPM density in the sky between east latitude 120 and 130 degree along the north latitude 32 degree. We discovered the following:
1. SPM clusters were often found in the upper sky on the west area from 120 degree of east latitude. Physically considering the particle density, it is natural to find the concentration in the lower sky. However, if there is a jet stream in the upper air-layer, and the SPM cluster moves with the stream; the upper SPM concentration would be found. On the Lider observations, we often find such SPM clusters.
2. Absorptions were found clearly in the blue band of the moonlight spectrum. It shows a localized SPM cluster in the upper sky. The absorptions are round in the case of the lower sky. Since the ray passes through long distances, the absorptions were averaged about many kinds of different SPM clusters.
3. On the west area from 120 degree of east latitude, there is no relation between the SPM density on the ground and the intensity of the red-band of the moonlight spectrum. On the east 131 degree, the relation is found obviously. Thus, it is certain that we find orange moons in every lower sky.
4. There is invisible mist in the stratosphere from 120 degree of the east latitude.
From these observations, we believe that the characters of the SPM are changed in moving 10 degrees of the east latitude.
Keywords: Suspended particulate matter, Moonlight spectrum, Upper air contamination, Color index
Text in Japanese(HTML)
PDF file on J-STAGE