The daytime sky at Toyohashi city was observed every five seconds from April 2021 to December 2021 by using two all-sky cameras. Based on the images, the number of the cloud layer was statistically analyzed for every hour. The results indicate that two-layer clouds occupy a large temporal fraction as well as one-layer clouds. Therefore, the motion of the two-layer clouds was examined by the optical flow analysis with Lucas-Kanade method. Two directions were clearly obtained from the polar histogram of the angle of the optical flow vectors.
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